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Urine patches from grazing ruminants contain high concentrations of nitrogen (N) and are the main source of N leaching from grazed pastoral farming systems. While there have been various options identified to substantially reduce N leaching, in general these practices increase the cost of production or reduce production per hectare. In New Zealand, multi‐species pastures were evaluated as a cheaper option that would potentially retain productivity. Early research showed these pastures had lower urinary N excretion from grazing animals and increased plant N uptake, compared with standard New Zealand perennial ryegrass/white clover (PR‐WC) pastures. Further research highlighted the beneficial attributes of the pasture herb narrow‐leaved plantain (Plantago lanceolata; PL), specifically: reduced urine N concentration, reduced urine N excretion, and reduced rate of soil nitrification. Significant reductions (14%–89%) in N leaching were found from cow urine applied to lysimeters with pastures including PL, compared with PR‐WC pasture. Paddock‐scale measurements confirmed the effects of PL, with 20%–60% lower N leaching when PL comprised 30%–40% of the dry matter (DM) of PL‐PR‐WC grazed pastures. There were no negative effects on milk production and composition when feeding PL to dairy cows, but small positive effects on fatty acid profiles. However, weed and pest management, palatability and persistence remain challenging in pastures containing PL on commercial farms. Management options need to be clarified to ensure successful establishment and maintenance of PL. Additionally, the cultivar differences in secondary compounds and their impact on nitrification rate and N leaching need to be better understood. [ABSTRACT FROM AUTHOR]

Context: Biological nitrogen (N) fixation through the rhizobia–legume symbiosis is a sustainable and cost-effective source of N for agriculture. In New Zealand (NZ), white clover (Trifolium repens) is a key component of pastures and rhizobial inoculation of clover is widely used. The current commercial inoculant for white clover, TA1, was isolated in Australia in the 1950s and may not be the best partner for modern white clover cultivars. Aims: To identify Rhizobium leguminosarum bv. trifolii (Rlt) isolates suitable for use in NZ pastures. Methods: The symbiotic potential of >230 isolates collected from throughout NZ was evaluated in plant bioassays. Selected isolates were further evaluated in pot and field trials. Key results: Approximately 40% of NZ isolates supported better clover growth than TA1 under N-limited conditions in vitro. Of 24 Rlt isolates evaluated in a glasshouse trial, five produced significantly higher clover biomass than TA1. Three (S11N9, S20N7, S4N6) of nine isolates evaluated in two field trials in 2018–2019 significantly increased clover growth (12–38%) compared with paired uninoculated clover at several harvests, whereas inoculation with TA1 did not improve yield. In a third trial in 2020, S11N9 and S20N7 increased clover growth compared with the uninoculated control at two of three harvests; S4N6 performed better than TA1 at one harvest. When tested with four white clover cultivars, five Rlt isolates had higher symbiotic potential than TA1. Conclusions: Inoculating white clover would be beneficial if improved inoculant isolates were available. Implications: We recommend some NZ Rlt isolates could be developed into commercial inoculants to improve white clover performance in NZ. Enhancing biological nitrogen fixation through the rhizobia–legume symbiosis is urgent, as concerns over environmental impacts of intensive agriculture increase. Despite the importance of legumes in New Zealand's pastures, there has been little emphasis placed on rhizobium, and modern white clover cultivars still rely on a commercial inoculant TA1 isolated from 1950s. A few rhizobial isolates identified in this study performed better than TA1 and could be developed into commercial inoculants to improve white clover performance in New Zealand. [ABSTRACT FROM AUTHOR]

Context: Tagasaste (Cytisus proliferus), a fast-growing leguminous tree, has potential to supplement pasture production in steep-hill country and to increase pasture resilience. Aims: In the companion paper, we quantified tagasaste production characteristics. Here, we determine the effect of proximity of 10-year-old tagasaste trees on productivity of eight pasture species including grasses (perennial ryegrass, Lolium perenne ; cocksfoot, Dactylis glomerata ; prairie grass, Bromus willdenowii ; microlaena, Microlaena stipoides), perennial legumes (white clover, Trifolium repens ; red clover, T. pratense ; lotus, Lotus pedunculatus), and an annual legume (subterranean clover, T. subterraneum). Methods: A site was established in the East Coast region of the North Island of New Zealand on steep-hill country (>20° slope). Herbage production, nutritive value and survival of pasture species established as spaced transplants were measured over 3 years. Results: Cocksfoot had high survival, herbage production and metabolisable energy content but was negatively affected by proximity to tagasaste. Microlaena was not significantly affected by proximity to tagasaste; however, it was much less productive and had lower nutritive values than the other grasses. Only 40% of perennial ryegrass transplants survived 3 years, and survival of perennial legumes was negligible. Subterranean clover was able to set seed in the open and in shade. Conclusions: Cocksfoot was the most productive grass species, and microlaena was least affected by proximity to tagasaste. Given the poor persistence of perennial clovers, annual clovers may be better suited to a tagasaste silvopasture on steep, dry hillsides. Implications: Mixtures of cocksfoot and subterranean clover may be well suited to summer-dry hillsides, between and under trees in a tagasaste silvopasture. Microlaena may provide some forage and can maintain groundcover despite shade. Growth and survival of eight pasture species in proximity to the forage shrub tagasaste were quantified in drought-prone hill country. Cocksfoot and subterranean clover were highly productive only in lightly shaded areas, whereas microlaena, although less productive than other grasses, was not significantly affected by shade treatment, and perennial legumes showed negligible survival. Cocksfoot and subterranean clover could be established between trees in a tagasaste silvopasture, with naturalised microlaena maintained beneath the canopy to provide groundcover. [ABSTRACT FROM AUTHOR]

Legumes have underpinned transformational change on New Zealand sheep and beef farms over the last 30 years. This was through an emphasis on ewe nutrition based on lucerne or red clover dominant pastures, and increased use of subterranean and white clovers on uncultivatable hill country. Pre- and post-weaning lamb growth rates have increased, and enabled earlier slaughter of heavier lambs. The farm systems results include greater numbers of hoggets mated, higher lambing percentages and greater ewe efficiency (kg lamb weaned/kg ewe mated). Extension packages to support legume use have compared growth rates of resident and legume-based pastures, economic analyses of successful farms and management packages for the most appropriate legume in different environments. Over the same period, the dairy industry rapidly expanded in cow numbers and area onto flat irrigated land on the Canterbury Plains. The nitrogen deficiency of perennial ryegrass was overcome by a linear increase in nitrogen fertiliser use. Environmental concerns from this intensification has led to a legislated nitrogen cap of 190 kg/ha.year. This, coupled with a recent trebling in urea price, has returned attention to increasing the white clover content of these pastures. Nitrogen applications can be minimised by using diverse pastures sown with a legume, herb and <8 kg/ha of perennial ryegrass. Work on other legumes, including annuals and those with condensed tannins, has to date failed to increase their use in most pastoral settings, with the exception of the perennial lupin which is adapted to high-aluminium soils in the South Island High Country. Legumes have underpinned the New Zealand pastoral-based economy for over 100 years. White clover remains the most widely sown, but specialist red clover based pastures are providing high quality feed for fattening livestock in wetter regions of the country. In the drier east coast, lucerne management has been refined based on crop physiology principles. This has allowed earlier lambing, leading to transformational change on-farm. Subterranean clover remains the dominant annual legume used. Successful integration of legumes on-farm has required understanding of the genotype by environment by management interactions. [ABSTRACT FROM AUTHOR]

International seed trading provides a significant introductory pathway for weed seeds, and many globally established weeds originated as contaminants in agricultural seed lots. Management of these trade systems helps minimize agricultural losses and is an important means of preventing future biological incursions. Forage crop seed lots could be considered higher risk than seed lots of arable and vegetable crops, as they have been found to have a higher percentage of contaminated seed lots. Two of the most commonly used temperate forage crops worldwide are perennial ryegrass (Lolium perenne) and white clover (Trifolium repens). New Zealand is one of the top producers of these crop seeds globally, and both species are commonly used in New Zealand pastures. Using historical and current seed lot analytical purity test results, we examined the frequency, identity and temporal changes of weed seeds found within agricultural seed lots of perennial ryegrass and white clover grown in New Zealand from 1912 to 2019. Overall, the percentage of contaminated forage seed lots decreased between approximately three to sixfold over the study period, indicating that herbicide availability, seed certification and improved crop management have been effective for weed control. However, we identified a handful of annual weed species that could become more problematic in the future, either because they showed an increasing presence trend in seed lots or were identified as the most common contaminants. In 2019, Vulpia bromoides was the most common contaminant in perennial ryegrass seed lots, and Chenopodium album was the most common in white clover seed lots. Sherardia arvensis and Poa annua, both significant species with an increasing presence trend, had the largest increases in perennial ryegrass seed lots over the study period. Conversely, Rumex acetosella had the largest presence decline for both crop species. There was a significant difference between the percentage of contaminant species that were grass weeds between study crops, where perennial ryegrass seed lots had approximately four times more grass species than white clover. Considering New Zealand trades crop seed with approximately half of the world's countries and contributes substantially to the global supply of forage seed, our study provides a unique insight into changes of the weed spectrum throughout the seed for sowing system over the last century. [ABSTRACT FROM AUTHOR]

Background: Experimental work using pot trials and mesocosm studies has indicated that species combinations are more effective than single species mitigating the soil nutrient constraints that limit pasture productivity in New Zealand's hill country, but there is little field evidence to support this. Aim: We question whether coexistence of species provides an opportunity to facilitate enhanced uptake and improved procurement of key soil nutrients in these mid-altitude grasslands. Methods: Native and exotic legumes and co-occurring plant species were sampled according to whether they were growing together in close proximity or in single species patches. Foliar concentrations of nutrients were compared. Results: Nutrient concentrations in a native broom, Carmichaelia petriei, were higher when it was growing in combination with native tussock grasses. Higher concentrations of eight nutrients were recorded in foliage of an exotic legume, Lotus pedunculatus, when it was growing with native grasses or within the acuminate foliage of Aciphylla aurea (golden spaniard). Foliar concentrations of only P and Mn were elevated in white clover (Trifolium repens) foliage when it was growing in combination with grasses. Conclusions: These findings point to mutual facilitation of nutrient uptake by combinations of species growing together. Some species that are less desirable from an agricultural perspective improve acquisition of soil nutrients by the plant community. Novel native species assemblages represent a potential opportunity to refine pasture management, facilitating optimal exploitation of nutrients. This could reduce fertiliser requirements and enhance and protect native biodiversity in pastoral grasslands. [ABSTRACT FROM AUTHOR]

The expanded usage of white clover has increased the importance of understanding white clover dynamics in pastures. It is assumed that clover plants have a higher tolerance for moisture and nutrient deficiencies when the taproot is still present. Therefore, the survival of the seminal taproot can influence the dynamics of clover. Past breeding efforts in countries like New Zealand have focussed on increasing the taproot longevity through hybridisation with a close relative of white clover. However, there is no direct evidence whether increased survival of the taproot results in increased performance of white clover. In this study, we aimed to (i) assess the relationship between taproot volume and taproot survival, and (ii) whether the timing of death of the seminal taproot influences the population dynamics of white clover varieties. In a two‐year field experiment with 18 white clover varieties grown in monoculture and in mixture with Lolium perenne L, the taproot characteristics and population dynamics were studied. It was shown that taproot volume was positively correlated to both leaf size and taproot presence during autumn 2017, 1 year after sowing. The combination of the timing of death of the seminal tap root and the development of stolons seems to play a more important role in increasing the persistence of white clover than the absolute survival of the seminal taproot. Future research should focus on understanding the transition from a taprooted white clover to a stolonous white clover plant in relation to specific weather events such as winter frost conditions. [ABSTRACT FROM AUTHOR]

Perennial ryegrass (PRG, Lolium perenne L.) breeding effort in New Zealand (NZ) has increased since c. 1990, resulting in greater functional trait diversity (e.g. heading date, ploidy, and associated Epichloë endophyte strain) in commercial products. This study quantified the variation, associations and interactions in dry matter (DM) yield, nutritive value and persistence‐related traits among commercial cultivar‐endophyte combinations released between 1973 and 2012, as a basis for assessing gains in value being delivered to the pasture‐based livestock industries. Twenty‐four or 28 combinations were compared over 3 years in two trials in each of two regions: Waikato in northern NZ (dryland), and Canterbury in central eastern South Island (irrigated). Cultivar‐endophyte combinations were sown in mixtures with white clover, and pastures were intensively grazed 8–11 times per year by dairy cows. Principal Component Analysis identified 4 distinct clusters for the DM yield variables and for metabolisable energy (ME) content in each of the four trials. A broadly‐adapted group of three late‐season flowering, AR37‐infected diploids with NZ and Spanish breeding backgrounds dominated the highest‐yielding clusters. Tetraploids dominated the high ME content clusters. Interactions with region were observed throughout the data set: the strongest of these was driven by endophyte strain effects in Waikato. High‐yielding cultivar‐endophyte combinations in these trials were also generally high‐yielding in the standard cultivar merit testing system operated in New Zealand, as interpreted via the DairyNZ Forage Value Index. However, alignment was poorer for medium‐ and lower‐yielding cultivar‐endophyte combinations. Several implications for forage evaluation methods and end‐user industries are identified. [ABSTRACT FROM AUTHOR]

BACKGROUND: The setting and following of phytosanitary standards for weed seeds can lessen the impacts of weeds on agriculture. Standards adopted by seed companies, laboratories and regulators ensure the contamination rates do not exceed some thresholds. Globally sample size standards are set based on the amount needed to obtain a contaminant in a random sample of the seed lot, not detectability. New Zealand requires a 95% confidence that the maximum pest limit of 0.01% of quarantine weed seed contamination is not exceeded in an imported seed lot. We examined 24 samples each containing approximately 150 000 seeds of either perennial ryegrass (12 samples) or white clover seeds (12 samples) that were then spiked with seeds (contaminants) from 12 non-crop species (3–8 seeds of each). We considered factors that may impact detection rates: shape, color, size, and texture relative to the crop, and technician (including a commercial seed laboratory). RESULTS: A linear mixed model fitted to the data indicated significant observer, crop, and seed color, shape, and size effects on detection. Detectability increased by 20% ± 7.7 (± standard error) when seeds had a distinct shape or color (28% ± 8.1), or were larger (23% ± 8.7) rather than smaller, relative to the crop. Commercial laboratory identifications were usually correct at the level of genus, and species for common weeds, but some misidentifications occurred. CONCLUSION: Sample sizes for border inspections should be based on detectability of regulated weed seeds in the crop in combination with weed risk for the crop and location. [ABSTRACT FROM AUTHOR]

Historic pollination networks are important to understand interactions between different plant and pollinator species, as well as to differentiate between causes and consequences of present insect population decline. Natural history collections in museums store biological proxy data, which is used to reconstruct historic pollination networks of bumble bees. Four bumble bee species (Bombus terrestris, B. ruderatus, B. hortorum and B. subterraneus) were introduced to Aotearoa New Zealand in 1885 specifically for pollination purposes. Pollen samples were collected from museum specimens of three of the four NZ species of bumble bee (excluding B. subterraneus) collected between 1954 and 1972 from 56 locations across the South Island, New Zealand. The most common plants identified on all three bumble bee species were Calluna vulgaris (heather), Ulex (gorse), Cytisus (broom), and Trifolium repens (white clover). However, all three bumble bee species also carried pollen from several native plants (e.g. Arthropodium, Weinmannia, Plagianthus, Quintinia, Veronica, Melicytus) and potentially had been involved in the pollination of these species. This study adds new plant species known to be foraged upon by bumble bees in Aotearoa New Zealand. Further studies on pollination networks in New Zealand will help us understand any changes in host plant preferences over time and after the time period covered by this study. [ABSTRACT FROM AUTHOR]

Grapevine leafroll disease (GLD) affects grapevines worldwide. The primary causal agent of GLD is grapevine leafroll-associated virus 3 (GLRaV-3), which spreads to uninfected grapevines via mealybugs and soft-scale insects. Pseudococcus calceolariae (Hemiptera: Pseudococcidae) is a mealybug vector of GLRaV-3 in New Zealand. P. calceolariae also colonizes clovers (Trifolium spp.) growing naturally as vineyard ground cover. Separating mealybug from GLRaV-3 grapevine host could be enhanced by a trap plant: an alternative host attractive to and retentive of the target pest. We evaluated the association between P. calceolariae and ‘Grasslands Huia’ white clover (GHWC). GHWC seed was sown under grapevines in a commercial vineyard (14 × 0.4 ha plots); the control was under-vine herbicide use (7 × 0.4 ha plots, where only few Trifolium spp. plants grew). After 2 years, GHWC cover peaked at 40% mealybug infestation in 2019. From 2018 to 2021, P. calceolariae detection and abundance on GHWC was significantly higher than plants from the control plots. There was no treatment effect for mealybug infestation of grapevine leaves nor of GLRaV-3 incidence, independent of vintage. A glasshouse trial found no transmission of GLRaV-3 by P. calceolariae to any of 256 plants among five clover cultivars tested (Trifolium spp.), including GHWC; mealybug transmitted GLRaV-3 to 35 of 107 Nicotiana benthamiana plants. The results showed that in the 5-year period, added GHWC did not decouple P. calceolariae from the grapevine to reduce GLRaV-3 incidence, but rapid colonization of GHWC by mealybug and the lack of GLRaV-3 transmission to GHWC are encouraging. Further evaluation is needed to assess whether plant biodiversity can benefit a GLRaV-3 ecological management objective. [ABSTRACT FROM AUTHOR]

White clover (Trifolium repens) is integral to mixed pastures in New Zealand and temperate agriculture globally. It provides quality feed and a sustainable source of plant-available nitrogen (N) via N-fixation through symbiosis with soil-dwelling Rhizobium bacteria. Improvement of N-fixation in white clover is a route to enhancing sustainability of temperate pasture production. Focussing on seedling growth critical for crop establishment and performance, a population of 120 half-sibling white clover families was assessed with either N-supplementation or N-fixation via inoculation with a commercial Rhizobium strain (TA1). Quantitative genetic analysis identified significant (p < 0.05) family additive genetic variance for Shoot and Root Dry Matter (DM) and Symbiotic Potential (SP), and Root to Shoot ratio. Estimated narrow-sense heritabilities for above-ground symbiotic traits were moderate (0.24-0.33), and the strong (r = 0.97) genetic correlation between Shoot and Root DM indicated strong pleiotropy or close linkage. The moderate (r = 0.47) phenotypic correlation between Shoot DM under symbiosis vs. under N-supplementation suggested plant growth with mineral-N was not a strong predictor of symbiotic performance. At 5% among-family selection pressure, predicted genetic gains per selection cycle of 19 and 17% for symbiotic traits Shoot DM and Shoot SP, respectively, highlighted opportunities for improved early seedling establishment and growth under symbiosis. Single and multi-trait selection methods, including a Smith-Hazel index focussing on an ideotype of high Shoot DM and Shoot SP, showed commonality of top-ranked families among traits. This study provides a platform for proof-of-concept crosses to breed for enhanced seedling growth under Rhizobium symbiosis and is informative for other legume crops. [ABSTRACT FROM AUTHOR]

Clover yellow mosaic virus (ClYMV) is reported for the first time in two cultivars of ornamental verbena (Verbena X hybrid) from Christchurch in New Zealand. Sequencing of a ~ 500 bp fragment of the 8 KDa triple gene block and coat protein partial genes indicated the NZ isolates were closely related to ClYMV from verbena in the UK and Poland and more distantly to isolates from clover in Australia and Japan. ClYMV has been intercepted in quarantine in tulips and detected in white clover in Auckland; the verbena isolates may represent a separate incursion into NZ. [ABSTRACT FROM AUTHOR]

Analyses of New Zealand farm systems require estimates of herbage yield and quality. These are available for perennial ryegrass and white clover pastures but not for other common pasture species. We used five lucerne datasets to derive functional relationships between growth rate and temperature. This required three functions to account for partitioning in lucerne between spring and autumn and differences between seedling and regrowth crops. The maximum mean daily growth rate of 206 ± 5.95 kg DM/ha/d occurred with full canopy cover at mean air temperatures between 15°C and 22°C. This represents the upper end of the temperature range available. The relationship was summarised into a matrix that could be incorporated into existing forage forecasters for farm system analyses. Alternatively, a simplified model assessed growth rate in relation to thermal time. This showed after 140°Cd accumulated from 1 July, lucerne initiated spring growth at 11.9 kg DM/ha/°Cd until mid-January and then decreased to 6.7 kg DM/ha/°Cd from mid-January to 30 June for fully irrigated crops. An exponential heightchron relationship was also calculated to estimate crop height based on the thermal time required per mm as photoperiod changed. This relationship allows lucerne quality to be predicted from the leaf:stem ratio. [ABSTRACT FROM AUTHOR]

Background: Combinations of grasses and nitrogen-fixing legumes are ubiquitous in most natural and derived pastoral grasslands. This was not formerly the case in New Zealand's unique indigenous grasslands that are now frequently impacted by exotic pasture grasses and legumes. Understanding the co-existence of native and exotic plants is the broad focus of this research. Aims: Spillover of nitrogen (N) from clovers to grasses in diverse pasture is well known. We question whether grasses provide reciprocal nutritional benefits to legumes. Does the mutual exploitation of soil biogeochemistry by legumes and grasses help to explain their coexistence and, if so, does this have implications for biodiversity in NZ's novel native grassland communities? Methods: Combinations of grasses and legumes, including a native tussock grass, were grown in a nutrient-poor (low P, S, Ca, Mg, Mn, and B) high country soil in a pot experiment, quantifying the foliar acquisition of nutrients from soil. Field data were obtained by sampling foliage of clover in single- and mixed-species patches in a more fertile lowland pasture. Results: Benefits of legume and grass growing together were reflected in enhanced productivity and higher uptake of a range of key nutrients. This was most evident but not restricted to a combination of two exotic species: cocksfoot and white clover. In the nutrient-poor soil, legumes grew better in combination with different species of introduced grasses. Uptake of key elements from soil to plants significantly differed with combinations of legumes and grasses compared to individual species. Elevated concentrations of P, K and S were recorded in clover when growing with grasses, although Ca uptake was lower. Expected reciprocal reduction of clover N or enhanced grass N were not recorded. Mass balance data (total extraction of key nutrients from the soil pool) showed that combination of grasses and legumes exploit soil nutrients (particularly P, Zn, Mn and Mo) more effectively than single species alone. In grasses, only tissue concentrations of K, S and Zn significantly increased when growing with legumes, but native tussock grass procured less nutrients when growing with the exotic legumes. Field sampling of clover from the more fertile lowland soil showed significantly higher foliar concentrations of K, Mn, Cu and B, but less Ca. Conclusions: The findings are indicative of a mutualistic relationship: legumes derive nutritional benefits from growing with grasses. Native tussock grass contained less N when growing with the exotic legumes, suggesting less compatibility and a lack of adaptation to coexistence. [ABSTRACT FROM AUTHOR]

Globally, the soils underlying managed grasslands are an important reservoir of carbon (C), with the management of the land strongly influencing whether the soils gain, lose or maintain C. Further, improved grassland management, such as rotational grazing and increased sward diversity, are widely promoted to increase soil C sequestration despite limited evidence. Using data from New Zealand's grazed dairy grasslands, we examined the effect of management practices on C stocks through measurement of the net ecosystem C balance (NECB) across 68 site-years. Management practices tested included year-round rotational grazing, differing pasture sward composition, irrigation, periodic supplemental feed cropping and pasture renewal. Excluding years where supplemental feed cropping occurred, the mean (±95% confidence interval) NECB was −12 ± 30 g C m−2 y−1 (65 site-years; the negative value represents C loss), indicating the soil C stocks of these ecosystems were likely near steady-state. The processes of pasture renewal and the transition between pasture and crops resulted in reduced C inputs from photosynthesis of between −232 and −94 g C m−2. This reduced C input was partially overcome with the application of effluent or manure at the time of cultivation where applied. There was no difference in NECB between irrigated (−26 ± 114 g C m−2 y−1) and non-irrigated (−19 ± 198 g C m−2 y−1) pastures. In general, conventional ryegrass/white clover pastures were more beneficial for C stocks than alternative pasture species and mixes. Periodic cropping for supplemental feed resulted in C losses, with the magnitude depending on crop type and management, although data were limited to three site-years. [Display omitted] • Carbon (C) balances of grazed flat-land dairy pastures were near steady-state. • C loss during pasture and crop establishment depended on time to net CO 2 uptake. • Ryegrass/white clover pastures were better for C stocks than alternative swards. • Irrigation had inconclusive effects on C balance and may depend on pasture species. [ABSTRACT FROM AUTHOR]

Fifteen lambs from a flock of 1,000, 5-month-old Romney lambs in the Manawatū region of New Zealand, developed unusual postural and gait abnormalities during the summer of 2020. In mid-January, the lambs were grazing a raphanobrassica crop (xRaphanobrassica; Brassica oleracea x Raphanus sativus) but were removed from this crop soon after as they developed dermal lesions on the pinnae consistent with photosensitisation (colloquially known as "rape scald"). The lambs were placed onto a shaded paddock containing a pasture of predominantly perennial ryegrass (Lolium perenne) and white clover (Trifolium repens). One week following removal from the crop (late January), the 15 lambs developed abnormal postures and gaits that were described by farm staff as "neurological" and "swayback-like". From a distance, all 15 lambs exhibited remarkably similar abnormal posture and gait whereby their weight was borne on their carpi, and they appeared to crawl while walking due to crouched hindquarters and prominent lordosis. Of the affected lambs, five were submitted for clinical examination. All five had normal vital signs. The results of neurological examinations were within normal limits. In response to palpation of the dorsum, the lambs performed an exaggerated and unusual dipping motion, particularly when pressure was applied over the lumbar spine. Parting of the fleece over the dorsum revealed thickened, indurated skin that cracked and tore easily. The shorn pelt of a euthanised lamb revealed a large (100 cm × 40 cm), locally extensive, irregular ovoid region of the skin of the dorsum that was markedly thickened, indurated and crusted. Impression smears of the lesions revealed long filamentous chains of plump coccoid bacteria separated by transverse and longitudinal septa, consistent with Dermatophilus congolensis. Histopathology of the lesions revealed severe, chronic-active, locally extensive, necrosuppurative dermatitis with marked acanthosis, orthokeratotic and parakeratotic hyperkeratosis, ulceration, filamentous bacteria and coccoid zoospores. Cutaneous dermatophilosis due to Dermatophilus congolensis. Painful dermal lesions due to severe dermatophilosis of the dorsal skin of sheep are capable of causing postural and gait abnormalities that may be misinterpreted as signs of neurological abnormality. Such dermal lesions may be concealed by an apparently normal fleece. [ABSTRACT FROM AUTHOR]

Assessment of the relative performance of white clover (Trifolium repens L.) cultivars, using multi-year and multi-location seasonal growth trials, is key to identification of material with specific and broad adaptation. This paper is based on a multi-year and multi-location study of 56 white clover entries comprising 14 commercial cultivars and 42 experimental synthetic lines evaluated for seasonal growth under rotational grazing across four locations in New Zealand over 4 years. The four locations (and animals grazing) were: Kerikeri (beef cattle), Aorangi (beef cattle), Ruakura (dairy cattle), Lincoln (sheep). Significant (P < 0.05) genotypic variation among the 56 entries, and genotype × year, genotype × location and genotype × season interactions, were estimated. We were able to identify cultivars and experimental synthetics with specific and broad adaptation to the three grazing management types. Cvv. AberDance, Apex, Demand, Prestige, Quartz and Riesling, with leaf size ranging from small to medium–large, showed highly above-average performance under sheep grazing. Synthetic lines 15 and 45 also had highly above-average performance under sheep grazing. Cvv. Legacy and Kopu II showed above-average performance under cattle and dairy grazing. Synthetics 15, 48, 49, 44, 22 and 18 and cv. Quartz had above-average performance under all three grazing managements. Synthetics 27, 33 and 38 had highly above-average performance across all three grazing managements and were superior to all 14 cultivars evaluated. Several of these superior synthetics are being tested across multiple grazing environments. Among the 14 cultivars evaluated, Legacy and Quartz showed superior seasonal growth performance across the three grazing managements. Quartz is being evaluated in several on-farm trials across temperate regions of the world. Fourteen white clover cultivars and 42 experimental synthetics were evaluated for seasonal growth under beef cattle, dairy cattle and sheep grazing across 4 years. Entries with specific and broad adaptation to the three grazing management types were identified. Cv. Legacy was more responsive to cattle and dairy grazing, and cv. Quartz to sheep grazing. Synthetics with specific and highly above-average performance across all three grazing managements, superior to the cultivars, were identified. [ABSTRACT FROM AUTHOR]

Aims: The influence of soil edaphic factors on recruitment and composition of bacteria in the legume nodule is unknown. Typically, low (acidic) pH soils have a negative effect on the plant‐rhizobia symbiosis and thereby reduce clover growth. However, the specific relationship between soil pH and the ecology of rhizobia is unknown, in either their free‐living or nodule‐inhabiting states. We used New Zealand pasture systems with soils of different pH, and white (WC) and subterranean (SC) clovers, to examine the relationship between soil pH and the diversity of bacteria that inhabit the nodules. Methods and Results: Amplicon sequencing (16S rRNA) assessed the bacterial community in 5299 nodules recovered from both legume species grown in 47 soils of different edaphic (including pH) properties. Fewer nodules were formed on both clovers at low soil pH. As expected, rhizobia comprised ∼92% of the total reads in both clovers, however 28 non‐rhizobia genera were also present. Soil pH influenced the community structure of bacteria within the nodule, and this was more evident in non‐Rhizobium taxa than Rhizobium. Host strongly influenced the diversity of bacteria in the nodules. The alpha diversity of nodule microbiome in SC nodules was higher than in WC nodules and SC nodules also harbored a higher relative abundance of non‐Rhizobium bacteria than WC. Beta diversity of Rhizobium and non‐Rhizobium bacteria was influenced more by clover species rather than edaphic factors. Conclusions: The results indicate that these clover species modified their nodule biomes in response to pH‐stress. Significance and Impact of the Study: The non‐Rhizobium bacteria may have some functional significance (such as improved clover persistence in low pH soils) in legume nodules. [ABSTRACT FROM AUTHOR]

Grapevine leafroll-associated virus 3 (GLRaV-3), an economically significant pathogen of grapevines, is transmitted by Pseudococcus calceolariae , a mealybug commonly found in New Zealand vineyards. To help inform alternative GLRaV-3 control strategies, this study evaluated the three-way interaction between the mealybug, its plant host and the virus. The retention and transmission of GLRaV-3 by P. calceolariae after access to non- Vitis host plants (and a non-GLRaV-3 host) White clover (Trifolium repens L. cv. "Grasslands Huia white clover"), Crimson clover (T. incarnatum), and Nicotiana benthamiana (an alternative GLRaV-3 host) was investigated. For all experiments, P. calceolariae first instars with a 4 or 6 days acquisition access period on GLRaV-3-positive grapevine leaves were used. GLRaV-3 was detected in mealybugs up to 16 days on non- Vitis plant hosts but not after 20 days. GLRaV-3 was retained by second instars (n = 8/45) and exuviae (molted skin, n = 6/6) following a 4 days acquisition period on infected grapevines leaves and an 11 days feeding on non- Vitis plant hosts. Furthermore, GLRaV-3 was transmitted to grapevine (40−60%) by P. calceolariae second instars after access to white clover for up to 11 days; 90% transmission to grapevine was achieved when no alternative host feeding was provided. The 16 days retention period is the longest observed in mealybug vectoring of GLRaV-3. The results suggest that an alternative strategy of using ground-cover plants as a disrupter of virus transmission may be effective if mealybugs settle and continue to feed on them for 20 or more days. [ABSTRACT FROM AUTHOR]

New Zealand pastoral productivity relies heavily on biological nitrogen (N) fixation from rhizobia bacteria. Cadmium (Cd), present in pasture soils as an impurity in phosphate fertilisers, may have toxic effects on both plant growth and rhizobia activity. Effects of Cd on growth of seedlings of a white clover cultivar 'Grasslands Tribute', in the absence and presence of the N2-fixing Rhizobium leguminosarum bv. trifolii strain TA1, were assessed in vermiculite microcosm assays. The lowest observable effect concentrations resulting in significantly lower white clover shoot weights than those grown without Cd were 0.07 mg Cd kg−1 (measured as Ca(NO3)2-extractable Cd, Cdextractable) in the absence of Rhizobium, and 2.33 mg Cdextractable kg−1 for Rhizobium-inoculated seedlings. Shoot N content was unaffected in white clover exposed to <5 mg Cdextractable kg−1. The results indicate symbiosis with Rhizobium strain TA1 conferred tolerance to white clover 'Grasslands Tribute' against Cd toxicity, and that this symbiosis is unlikely to be adversely affected by Cd concentrations reported (<0.003 mg Cdextractable kg−1) in New Zealand pasture soils. [ABSTRACT FROM AUTHOR]

In New Zealand, a commonly sown pasture combination is perennial ryegrass with white clover. The hydrothermal time model (HTT) was used to quantify germination under different temperature (T) and water potential (WP) conditions for white clover 'Nomad' and perennial ryegrass 'Stellar AR1'. Seeds were germinated in vitro under a range of T × WP combinations, and HTT models were fitted to germination time course data. Rapid germination of white clover under optimum T and WP was reflected by a much lower value for its HTT constant compared with perennial ryegrass (10.8 vs 80.7 MPa °C d). However, the lower base water potential for perennial ryegrass (−1.29 vs −0.495 MPa) and a higher threshold temperature for thermoinhibition (21.8 vs 18.3°C), meant that predicted perennial ryegrass germination was more resilient in warm dry conditions. HTT models can be used to assist decisions about the timing of perennial ryegrass and white clover sowing. [ABSTRACT FROM AUTHOR]

Growing a cover crop living mulch between plastic-mulched bedsmay reduce soil erosion while providing other agroecosystem services. However, information regarding the relative differences among living mulch species to maximize services and minimize competition for nutrients and water in adjacent plastic-mulched beds is limited. A 2-year experiment in Michigan evaluated nine living mulch species for biomass production, inseason weed suppression, and potential for cash crop competition. Species included three warm season grasses {Italian ryegrass [Lolium perenne L. ssp. multiflorum (Lam.)Husnot], teff [Eragrostis tef (Zuccagni) Trotter, and sudangrass [Sorghum bicolor (L.) Moench ssp. drummondii (Nees ex Steud.) de Wet & Harlan]}; three cool season grasses [barley (Hordeum vulgare L.), rye (Secale cereale L.), and wheat (Triticum aestivum L.)]; and three clover species grown in combination with rye {Dutch white clover (Trifolium repens L.), New Zealand white clover (T. repens L.) and yellow blossom sweet clover [Melilotus officinalis (L.) Lam.]}. Although all living mulch treatments significantly reduced in-season weed biomass relative to the weedy control in 2018, weeds were generally a dominant component of total biomass in all living mulch treatments other than teff. Weed biomass was negatively correlated with living mulch biomass, and teff exhibited both the greatest biomass and weed suppression in both years. However, despite spatial and physical separation, all living mulches demonstrated the potential to compete with a cash crop by reducing soil inorganic nitrogen and moisture levels in adjacent plastic mulch–covered beds. Growers interested in integrating living mulches into plasticulture systems must consider desired benefits such as enhanced weed suppression, soil quality, and harvesting conditions alongside potential risks to cash crop yields. [ABSTRACT FROM AUTHOR]

The soil fluorine (F) concentration in New Zealand agricultural soils has increased with time as a direct result of the widespread application of phosphate fertilizer to land. Elevated soil F concentrations may potentially harm soil microorganisms, which are important for nutrient cycling and soil formation. Rhizobium leguminosarum is a N2–fixing soil bacterium that is a fundamental component in New Zealand legume‐based pastoral farming. Any impact of F on Rhizobium leguminosarum would have an adverse effect on New Zealand pasture production. In this study, F toxicity to Rhizobium leguminosarum was examined as a first step to develop F guideline values for New Zealand agricultural soils. Bottle‐based experiments were conducted to examine the effect of the F− ion on Rhizobium–white clover (Trifolium repens L.) symbiosis by observing nodule morphology and growth. Results indicate that the F− concentration that causes 10% inhibition of Rhizobium respiration (IC10) for F− toxicity to Rhizobium leguminosarum was >100 mg F− L−1. Significant morphological changes occurred when Rhizobium was exposed to F concentrations of 500 and 1000 mg L−1. Both light and transmission electron micrographs confirmed that the Rhizobium leguminosarum–white clover interaction was not influenced by F− concentrations >100 mg L−1. The toxic F− concentration for Rhizobium leguminosarum determined in this study is orders of magnitude higher than the F− concentration in New Zealand agriculture soils under "normal conditions." There appears to be no indication of imminent risk of soil F to Rhizobium leguminosarum. [ABSTRACT FROM AUTHOR]

Pedigrees provide suitable input for tracking breeding crosses and monitor plants and animal populations. Pedigree analysis is an essential tool to visualize and describe population structure and genetic diversity. Pasture plant breeding relies on a range of strategies from closed system recurrent selection using elite cultivars to diversity‐focused programs using ecotypes and wild germplasm as parents. There is currently no published pedigree analysis of white clover (Trifolium repens L.), despite over a century of breeding efforts in New Zealand. A pedigree map was constructed for white clover germplasm stored in the Margot Forde Germplasm Centre located in Palmerston North, New Zealand. Inbreeding and kinship coefficients and the effective number of founders through time were estimated to assess genetic relatedness in the reference population. A total of 15,265 accessions were included in the map. The maximum number of traced generations was 15, and the mean completeness of parentage for the reference population was 72%. The mean number of offspring was 5.14. The origin of founding and introduced accessions was assessed. The effective number of founders was 175.68 or 17.5% of the total number of reference founders. Founding accessions and influencing ancestors were identified. One of the earliest parental accessions identified was 'North Canterbury Type I' from 1941. Relatedness was determined using the k coefficient, with k = 1 as complete relatedness. The overall mean relatedness was k = 0.002. Overall mean inbreeding level was 0.39%. Relatedness and inbreeding coefficients revealed distinct germplasm pools formed across time that are of interest to pre‐breeding efforts. [ABSTRACT FROM AUTHOR]

White clover (Trifolium repens L.) is a major contributor of productivity and ecological services in pastures and rangelands worldwide. White clover breeding is recognized as a priority in many countries with a pastoral‐based livestock productivity system. The objective of this study was to provide an updated estimate of the rate of change in genotypic value attributable to population improvement in white clover, using a set of 80 cultivars released between 1920 and 2010 by public and private plant breeding programs across 17 countries, in an experiment to evaluate forage yield across three locations in New Zealand. Overall, some New Zealand cultivars released in the 2000s were highly adapted to more stable testing environments. Geographic origin resulted in differential rates of gain. A segmental regression comparing the pre‐1965 and post‐1965 rates of gain was performed. The pre‐1965 regression line for white clover dry matter yield resulted in an absolute rate of increase of 0.031 g m−2 yr−1 decade−1 or 0.087% decade−1, whereas the post‐1965 line resulted in an absolute rate of increase of 0.058 g m−2 yr−1 decade−1 or 0.162% decade−1. White clover content resulted in a pre‐1965 absolute rate of increase of 0.011% content decade−1 or 0.032% decade−1 on average, and the post‐1965 line indicated an absolute rate of increase of 0.04% content decade−1 or 0.121% decade−1 on average. The comparisons between pre‐1965 and post‐1965 indicated a twofold increase for white clover dry matter yield and a fourfold increase in rates of gain for white clover sward content since 1965; however, the rate of gain remains below the theoretical potential. [ABSTRACT FROM AUTHOR]

Clovers (Trifolium spp.) are vulnerable to a large number of invertebrate pests so pest resilience amongst 19 leading commercial or near release New Zealand-bred clover cultivars was compared. Laboratory feeding choice tests comparing foliage from the test clovers against Grasslands Kopu II as the standard confirmed that red clovers (T. pratense) were less preferred than white clovers (T. repens) by adult clover root weevil and clover flea. Grey field slug showed no preference between red and white clovers, with the white clover Grassland Prestige performing the best. Porina larvae had lowest weight gains on strawberry clover (T. fragiferum). Subsequent tests using neonate greenheaded leafroller larvae and an artificial diet made with freeze-dried foliage from cultivars in the most and least preferred subgroups indicated antifeedant compounds, rather than leaf morphology, are likely responsible for differences in feeding preferences between red and white clovers. [ABSTRACT FROM AUTHOR]

Concern about the environmental biosafety of transgenic plants could be mitigated by the development of robust testing methods and selection of appropriate non-target (NT) test species. White clover (Trifolium repensL.) plants with either high or low hydrogen cyanide (HCN) levels were used as surrogate transgenic insecticidal and control plants, respectively. Survival, feeding, larval weight and fecundity of two grassland-dwelling native insects,Nicaeana cervinaBroun (Coleoptera: Curculionidae) andZizina oxleyiFelder & Felder (Lepidoptera: Lycaenidae), exposed to these plants were measured. For one of four assessments,Z. oxleyisurvival and larval weight was higher on high HCN plants. However, larval weight and developmental time was consistently lower for offspring of one of three parent butterflies irrespective of treatment. Weevil feeding was reduced on high HCN plants. Both test insect species were considered suitable for biosafety assays with genetically modified white clover, and the importance of considering genotype of test insects is discussed. [ABSTRACT FROM AUTHOR]

A set of 18 × 0.5 ha paddocks at the DairyNZ research farm in Hamilton made up from three replicates of six sward mixes had pasture collected weekly from 31 January 2012 to 9 May 2012 and spore counts ofPithomyces chartarumwere determined. Low diversity (LD) meant that the paddock was sown with a single grass species (tall fescue, high sugar cultivar, ryegrass) and white clover. High diversity (HD) meant that the paddock was sown with a single grass species and white clover plus prairie grass, chicory, plantain and lucerne. The study aims were to assess the benefit of diversity and sward type in the control of facial eczema. There was no difference in spore counts over time between high diversity and low diversity pastures (P = 0.43). Both tall fescue paddocks (LD and HD) showed a lower spore count over time in comparison with low diversity ryegrass (P = 0.055 and 0.05). [ABSTRACT FROM AUTHOR]

The nitrification inhibitor, dicyandiamide (DCD), can mitigate nitrate leaching and nitrous oxide emissions in New Zealand pastures and was commercially available to farmers until 2013, when its use was suspended due to detection of traces of DCD in exported milk. This prompted the investigation of the proportion of DCD taken up by pasture plants via foliage/roots. We measured the foliar and root uptake of DCD in two separate laboratory experiments using freshly collected in situ pasture cores (0-100-mm depth; 100-mm diameter) with a cover of ryegrass/clover. In the first experiment, DCD (10 kg ha) was sprayed onto the foliage of the cores that was analyzed over 21 days. In the second experiment, DCD was mixed thoroughly with the soil in the cores of two different soil types and repacked back into the cores and foliage analyzed over 37 days. Of the applied DCD, average foliar interception was 56 %, while 2.7 to 5.2 % of applied DCD was absorbed that did not change with time. Roots took up 2.6 to 6.3 % of applied DCD, which increased over time in both soils but with little pasture growth. After 97 days of application, no DCD was detected in the soil/roots. During the experimental period, we observed no change in the DCD concentration inside the pasture plants after uptake by the leaves or the roots. This DCD in pasture plants, if consumed by animals, may contribute to DCD in animal products. [ABSTRACT FROM AUTHOR]

A survey of 26 pastures was conducted and soil and plant material analysed for total cadmium (Cd) and phosphorus (P), and soils further analysed for a variety of edaphic properties. Background Cd in pasture soils ranged from 0.06–0.85 mg Cd kg−1soil (mean of 0.23) and correlated closely with total P (R2 = 65.5;P < 0.001), while weaker relationships with Olsen P, nitrate-N and calcium were evident. Cadmium in the pasture dry matter had no correlation to underlying soil total Cd (P = 0.113) or soil P (P = 0.75). Strains ofRhizobiumspp. were isolated from a reference soil high in Cd (Morrinsville; 1.34 mg Cd kg−1soil) and a mid-range Cd soil (Whataroa; 0.32 mg Cd kg−1soil). The IC50of these strains, along with the commercial inoculant for white clover (Rhizobium leguminosarumbv.trifoliiTA1), to Cd were tested using a respiration sensitive assay (MicroRespTM). Rhizobia from the Whataroa soil had significantly greater tolerance to Cd than those from Morrinsville soil (P = 0.008). We propose a general stress-tolerance mechanism has evolved in the rhizobia from Whataroa, conferring metal co-tolerance. The Cd IC50ofRhizobiumTA1 was 3.06 ppm, but levels of respiration inhibition were evident at lower concentrations. Given the importance of the legume:rhizobia symbiosis to New Zealand's pastoral sector, determination of ‘no observable effect concentrations' is required forRhizobiumspp., pasture legumes and, most importantly, the establishment and function of symbiosis (nodulation and N2fixation, respectively). [ABSTRACT FROM AUTHOR]

The distribution and abundance of cryptic viruses ( Partitiviridae) in natural and agricultural systems have received little attention. White clover cryptic virus-1 ( WCCV-1) was detected infecting white clover plants and seed growing in New Zealand, but was not detected in field collections and in only two of 114 seedlings grown from seed collected in eastern Australia using enzyme-linked immunosorbent assay and RT-PCR. WCCV-1 was detected at high incidences (14-48%) in the cultivars Huia, Kopu II and Tahora and at low incidences (0-7%) in Aran, Haifa, Ladino, Siral and Sustain white clovers. WCCV-1 remained viable in seed stored for 50 years. The results are compared with another group of obligate seed-transmitted pasture microbes: the fungal endophytes of perennial grasses. [ABSTRACT FROM AUTHOR]

Occasionally, exotic plant introductions lead to the emergence of an invasive insect within its native geographical range. Such emergence could be explained by a pre-adaptation of the insect to break through the defences of the new encountered host. We investigated the fitness responses of two New Zealand endemic scarabs (Costelytra brunneum and C. zealandica) when given a diet of an exotic pasture species, Trifolium repens, whose defences were artificially triggered by the phytohormone jasmonic acid. We found differential fitness responses between the two species when they were exposed to a defence-induced diet. We observed a significant weight increase in the invasive species C. zealandica when it was fed with treated roots compared with untreated controls, whereas no significant weight increase was observed in the non-invasive C. brunneum compared with the control treatments. Our study suggests that C. zealandica has a pre-existing ability to tolerate the defence chemicals of its exotic host and, more interestingly, to benefit from them, which may explain why this species has become a serious pest of pasture throughout its native geographical range. [ABSTRACT FROM AUTHOR]

The pasture growth module AgPasture was integrated into the APSIM (Agricultural Production System Simulator) simulation model, allowing pasture-based systems to be modelled in combination with other land uses at farm scale or within land use change studies. The model's predictions of pasture growth were evaluated against 32 pasture growth datasets from a diverse range of soil types and climatic zones across New Zealand. The pasture herbage accumulation simulated by the model closely matched actual measurements over varying intervals. Both predicted and measured pasture growth rate demonstrated the same seasonal pattern, including mean growth rate and inter-annual variation across measurement years. Predicted and measured annual average net herbage accumulation (NHA) on a dryland pasture was similar over 37 observation years (mean, 6.83 and 7.27 t DM/ha respectively; coefficient of variation, 29% and 27% respectively) and highly correlated (R 2 = 0.838, P < 0.0001; relative root mean squared deviation (RMSD) = 16%). The model's prediction of annual average NHA of all simulated pastures, spanning a wide range of pasture environments, also matched the measurement data well (R 2 = 0.777, P < 0.0001; relative RMSD = 21%). However, discrepancies between simulated and observed values occurred in some seasons and at some sites. Analysis of these discrepancies identified areas where the model could be improved by incorporating more accurate descriptions of the effects of plant development and grazing, soil temperature and the interactive effects of high temperature and soil moisture dynamics. [ABSTRACT FROM AUTHOR]

An outdoor study was conducted to examine relationships between plant productivity and stress-protective phenolic plant metabolites. Twenty-two populations of the pasture legume white clover were grown for 4½ months during spring and summer in Palmerston North, New Zealand. The major phenolic compounds identified and quantified by HPLC analysis were glycosides of the flavonoids quercetin and kaempferol. Multivariate analysis revealed a trade-off between flavonoid accumulation and plant productivity attributes. White clover populations with high biomass production, large leaves and thick tap roots showed low levels of quercetin glycoside accumulation and low quercetin:kaempferol ratios, while the opposite was true for less productive populations. The latter included stress-resistant ecotypes from Turkey and China, and the analysis also identified highly significant positive relationships of quercetin glycoside accumulation with plant morphology (root:shoot ratio). Importantly, a high degree of genetic variation was detected for most of the measured traits. These findings suggest merit for considering flavonoids such as quercetin as potential selection criteria in the genetic improvement of white clover and other crops. [ABSTRACT FROM AUTHOR]

White clover (Trifolium repens L.) is grown throughout New Zealand in pasture and as a seed crop in the South Island. This investigation was conducted to determine the number of honey bee visits necessary to fully pollinate white clover flowers; the number of foraging honey bees per hectare required to reach the maximum seed number per floret; and to assess the level of white clover pollination in Canterbury. The theoretical maximum number of seeds that can be produced per white clover floret is six, based on the number of ovules present. Based on the number of seeds resulting from a single bee visit (mean = 1.24), it is calculated that in an 8 h foraging day, 19,420 bees would be required per hectare to reach maximum seed number per floret, assuming that no floret received more visits than required. Bee activity was assessed at two clover sites with an estimated 20,124 foraging bees per hectare. This number should have been enough to reach maximum seed number per floret. However, seed set in these fields was approximately half of its theoretical potential. [ABSTRACT FROM AUTHOR]

The egg, larval, pupal and adult abundance of the clover root weevil Sitona lepidus Gyllenhal (Coleoptera: Curculionidae) was monitored at three sites for the first ten years following the discovery of this exotic pest in the Waikato region of New Zealand. The species went through an initial boom and bust cycle at two sites, with populations reaching up to 1800 larvae m-2. Thereafter, winter larval populations were relatively stable, ranging between 450-750m-2. Unlike in the Northern Hemisphere, S. lepidus was found to have two generations a year in the Waikato region of New Zealand. Pasture white clover content at the time of peak adult numbers was positively related to the subsequent peak larval populations for each generation. The factors contributing to the emergence of S. lepidus as one of the most important pasture pests in New Zealand are discussed. [ABSTRACT FROM AUTHOR]

Intensification in New Zealand dairy farming systems has placed greater pressure on clover performance and fitness and has highlighted the need to develop clover cultivars that are better adapted to intensive grazing systems. Increased stocking rates and increased use of nitrogen fertiliser have put enormous pressure on the contribution of clover to modern dairy systems. Future innovations such as semi-hybrid cultivars offer the potential to improve the competitiveness of legumes with nitrogen-fertilised forage grasses. Similarly, advances in condensed tannin research suggest that significant animal performance gains can be achieved in conjunction with reduced environmental impact. In order to capture these benefits, dairy farmers will need to reassess their grazing management to ensure that legumes can be maintained at economically useful levels. Novel grazing management systems that optimise the benefits provided by the grass and legume components need to be used in future dairy farming systems. Forage legumes, and especially white clover, have an important role to play in modern dairy systems. [ABSTRACT FROM AUTHOR]

Decision tree models were developed to investigate and predict the relative abundance of three key pasture plants [ryegrass (Lolium perenne), browntop (Agrostis capillaris), and white clover (Trifolium repens)] with integration of a geographical information system (GIS) in a naturalised hill-pasture in the North Island, New Zealand, and were compared with regression models with respect to model fit and predictive accuracy. The results indicated that the decision tree models had a better model fit in terms of average squared error (ASE) and a higher percentage of adequately predicted cases in model validation than the corresponding regression models. These decision tree models clearly revealed the relative importance of environmental and management variables in influencing the abundance of these three species. Hill slope was the most significant environmental factor influencing the abundance of ryegrass while soil Olsen P and annual P fertilizer input were the most significant factors influencing the abundance of browntop, and white clover, respectively. Soil Olsen P of approximately 10μg/g, or a slope of about 10.5° was critical points where the competition between ryegrass and browntop tended to come to an equilibrium. Integrating the decision tree models with a GIS in this study not only facilitated the model development and analyses, but also provided a useful decision support tool in pasture management such as in assisting precision fertilizer placement. The insights obtained from the decision tree models also have important implications for pasture management, for example, it is important to maintain a soil Olsen P higher than 10μg/g in order to keep the dominance of ryegrass in the hill-pasture. [Copyright &y& Elsevier]

Sixty-two white-clover pastures were tested by enzyme linked immunosorbent assay (ELISA) for five viruses (White clover mosaic virus(WClMV), Alfalfa mosaic virus(AMV), Red clover necrotic mosaic virus(RCNMV), Soybean dwarf virus(SbDV), beet western yellows virus(BWYV)) and also for members of the potyvirus group. Only one pasture was found to be virus-free. WClMV and AMV occurred, often at high incidences, on farms in every region. RCNMV and SbDV occurred in more than half the pastures whereas BWYV and potyvirus infection was less common. There was a general reduction in virus diversity with increasing latitude, with the most northern farms having greater species richness (all 6 viruses present) than those in Southland (1–3 viruses present). There was a significant relationship between the presence of AMV, BWYV, RCNMV, SbDV and irrigation. Dairy farming also had a positive relationship with BWYV, RCNMV and SbDV. WClMV increase was monitored in six pastures and incidence was observed to increase geometrically in young pastures. The relatively high incidence of RCNMV is in contrast to the findings of previous studies on white-clover pastures and indicates that assessing this virus's effects on white clover is of high priority. [ABSTRACT FROM AUTHOR]

White clover (Trifolium repens) fixes nitrogen and provides high-quality feed and is, therefore, a key contributor to New Zealand's grazed pasture systems. However, its productive potential is rarely reached due to abiotic factors (e.g. drought) and various biotic constraints, including nematodes. In a recurrent selection program based in the greenhouse, resistance to Meloidogyne trifoliophila and Heterodera trifolii has been improved and resistant lines have been crossed to cultivars to improve field performance. Tolerance to root-infecting nematodes and other factors has been improved in a field-based program in which the best performing plants were selected and crossed. In grazed field trials, lines from both programs performed as well or better than cultivar controls. Counts of nematodes in roots showed that resistance reduced numbers, but results varied among sites and years. This paper summarises progress made in white clover breeding programs in New Zealand and also examines advances in genetic mapping and introgression as they affect resistance to nematodes. The nematodes associated with pasture grasses are reported, together with observations which suggest that root-feeding nematodes have little impact on yield and that the animal toxicity associated with Anguina seed galls in Australia is absent from New Zealand. The effects of infection by endophytic fungi on nematodes parasitising grasses are also reviewed. [ABSTRACT FROM AUTHOR]

The dairy industry in New Zealand is a significant contributor (7% of GDP) to the national economy. Major current issues for the industry are the lack of cheap, highly-nutritive value feed for cows of high genetic merit for milk yield; the poorer reproductive capacity of these high merit Holstein-Friesian cows; the quantity and skill of farm labour; and the environmental consequences of intensive dairy farming. The industry has responded to these challenges in the following ways. Increased nitrogen fertiliser use has given increased pasture yields, but also increased nitrate leaching and nitrous oxide emission from farms, which in turn has led to research on wintering pads, diet modification and nitrification inhibitors to reduce N losses to the environment. Increased use of supplementary feeds has given improved milk yield per cow, but also increased total farm variable costs, labour requirements and nutrient losses, which in turn have fostered research for cheaper feeds and rumen modifiers to improve feed utilisation. The poorer reproductive performance of Holstein-Friesian cows with overseas genetics initially led to greater reproduction intervention treatments, but a greater awareness of welfare issues has encouraged increased use of crossbred Holstein-Friesian x Jersey cows to improve reproductive performance through heterosis. The use of larger herds and dairies initially allowed more efficient use of labour, but continuing problems with the cost and availability of labour has seen the adoption of once-daily milking on some farms and the experimental evaluation of automatic milking systems for pastoral systems. Future developments will include continued improvements in both quantity and quality of feed for cows of higher breeding worth, but more emphasis will be placed on traits such as feed conversion efficiency, health and survival in the herd. Automation of all farm tasks to reduce labour costs will be a major feature of future farms. Costs of environmental compliance will increase in the short-term until research delivers ways to reduce the carbon and nitrogen losses from grazing and cropping systems. [ABSTRACT FROM AUTHOR]

The effect of sowing date (SD) and sowing rate of perennial ryegrass (PRG) on the establishment of Caucasian and white clovers in New Zealand was assessed. Clovers were sown in spring on 24 September (SD1) and 9 November (SD2) 1999, and in autumn on 4 February (SD3) and 31 March (SD4) 2000. On each date, clovers were sown with 0, 3, 6 or 12 kg ha−1 of PRG. Total herbage dry matter (DM) production up to 6 November 2000 was 13–16 t DM ha−1 for SD1 and SD2 when sown with 3–12 kg ha−1 of PRG, and 7–10 t DM ha−1 for sown clover monocultures. For SD3 and SD4, total herbage production was 6–9 t DM ha−1 with PRG, while total herbage production of clover monocultures was 5·4 t DM ha−1 for SD3 and 2·6 t DM ha−1 for SD4. By 6 November 2000, white clover contributed proportionately more than 0·15 of herbage mass when sown with 3–12 kg ha−1 of PRG on SD1, SD2 or SD3, but less than 0·09 when sown on SD4. The proportion of Caucasian clover never exceeded 0·09 of herbage mass in any of the swards. White clover was successfully established in spring and in autumn with 3–12 kg ha−1 of PRG provided the 15-mm soil temperature was above 14 °C. None of the combinations of Caucasian clover and PRG provided an adequate proportion of legumes during the establishment year. This unsuccessful establishment of Caucasian clover with PRG was attributed to its inability to compete for available light as a seedling due to slow leaf area expansion from secondary shoot development and a high root:shoot ratio. Alternative establishment strategies for Caucasian clover may include the use of slow establishing grasses, cover crops and temporal species separation. [ABSTRACT FROM AUTHOR]

White clover (Trifolium repens L.) exhibits complex inheritance of seed production potential. Genome maps allow plant breeders to dissect the genetic control of complex traits into discreet factors with Mendelian inheritance, each of which is called a quantitative trait locus (QTL). A pair-cross between two highly heterozygous white clover genotypes created an F1 mapping population (n = 182) used to investigate the genetic control of seed yield (SY) and three component traits: inflorescence density (ID), yield per inflorescence (YI), and thousand-seed weight (TSW). Analysis of 3 yr of field data from a replicated trial in the primary seed production region of New Zealand indicated no strong correlations among the component traits. The ANOVA indicated significant genotype, year, and genotype × year effects for SY, ID, and YI; and genotype and genotype × year effects for TSW. Using genotype data for 209 microsatellite loci in the allotetraploid genome, the multiple QTL model analysis resulted in the discovery of 23 QTLs related to seed production in white clover. Both parent plants harbored beneficial alleles for SY and the three component traits. A region of the genome at the distal end of linkage group D2 was implicated in a number of traits related to seed production, and was strongly implicated in the control of YI and SY. The central region of linkage group C2 was strongly implicated in the control of ID and SY. Parent trait values were similar for ID, yet the population was highly variable for this trait and segregated for multiple QTLs, indicating the utility of this experimental design for QTL discovery in crosses among heterozygous individuals with similar phenotypes. Most QTLs were dominant, suggesting suitability for marker-assisted selection (MAS) in white clover. [ABSTRACT FROM AUTHOR]

White clover growing in New Zealand is experiencing increasing levels of ultraviolet-B (UV-B) radiation as a result of ozone depletion. We evaluated the effects of UV-B radiation on the foliar chemistry of two populations of white clover (Trifolium repens L.), ’Huia’ and ’Tienshan,’ and the consequences for the performance of armyworms (Spodoptera litura) and cutworms (Graphania mutans). Plants were grown in controlled environment rooms with and without supplemental UV-B radiation at a dose of 13.3 kJ m–2 day–1, corresponding to a 25% mid-summer ozone depletion above Palmerston North, New Zealand. In both white clover populations, UV-B radiation elicited changes in foliar chemistry, including slight increases in nitrogen concentrations and decreases in carbohydrate concentrations. In addition, the ’Huia’ population showed decreases in fiber concentrations and marked increases in cyanogenic activity. No change in UV-absorbing compounds was detected in either population. Long- and short-term feeding trials were conducted to assess dietary effects on insect growth, consumption, and food utilization. Changes in the performance of both insect species were generally small. The most pronounced effect was a 36% reduction in weight of S. litura after 2 weeks of feeding on Huia grown at high UV, but larval development times were only slightly prolonged and pupal weights were unaffected. S. litura short-term performance was affected by differences in white clover population. The long-term performance of G. mutans was not affected and its short-term performance (stadium duration and consumption rate) was only marginally affected by the high-UV treatment. We conclude that the effects of elevated UV-B radiation on white clover plant chemistry can be specific to certain plant populations. The differences in sensitivity of the two generalist insect species suggest that effects may also be specific to certain plant-herbivore associations. These results indicate that future UV-B herbivory studies should examine genotypic effects in both plants and animals. [ABSTRACT FROM AUTHOR]

Selections of white clover resistant or susceptible to Heterodera trifolii in earlier rounds of a recurrent selection programme were intercrossed and selected in three further rounds of selection. Resistance and susceptibility were measured by comparisons of cysts per gram of root dry weight (cpg). In the third, fourth, and fifth rounds of recurrent selection, the mean cpg of progenies from resistant parents was 23% (n = 974), 6% (n = 870) and 11% (n = 98) of that of progenies from susceptible parents. In each selection round, the resistant selections had 31, 4 and 7% of the number of cysts on susceptible selections. The percentages of immune plants (i.e. with 0 cysts) in the resistant groups were 1, 39, and 50% after the third, fourth, and fifth rounds of recurrent selection, respectively. Inoculum from 16 populations of H. trifolii from around New Zealand was added to two resistant and two susceptible white clover lines. After one generation of nematode development there were fewer cysts on the resistant lines for each population tested. Two resistant and two susceptible lines were compared in a glasshouse trial for their reaction to parasitism by H. trifolii . Infection reduced the shoot weight of all four lines but resistant lines grew better than either one or both susceptible lines at 109, 126, and 160 days after inoculation. In contrast, the uninfected lines did not differ in shoot weight over five samplings. More cysts were recovered from susceptible lines (means of 370 and 430 cysts per plant) than from resistant lines (means of 41 and 56 cysts per plant). Results indicate that development of a white clover cultivar resistant to H. trifolii is achievable and that the resistance will be effective against the nematode in most of New Zealand. The growth study indicated that advantages will be conferred in pastures where the presence of H. trifolii causes major limitations to white clover growth and persistence. Zusammenfassung- Die Wirksamkeit einer mehrfach wiederholten Selektion von Weissklee (Trifolium repens) auf Resistenz gegen das Kleezystenalchen (Heterodera trifolii)- In einem fruheren Selektionsprogramm gegen Heterodera trifolii resistente oder anfallige Weisskleeselektionen wurden gekreuzt und in weiteren Selektionsrunden selektiert. Resistenz und Anfalligkeit wurden durch Vergleich der Anzahl der Zysten je Gramm Wurzeltrockengewicht (cpg) bestimmt. In der dritten, vierten und funften Runde der Wiederholungsselektion betrugen die cpg-Werte bei Nachkommen von resistenten Eltern 23% (n = 974), 6% (n = 870) und 11% (n = 98) der Werte bei Nachkommen anfalliger Eltern. In jeder der Selektionsrunden hatten die resistenten Selektionen nur 31, 4 und 7% der Zystenzahlen an den anfalligen Selektionen. Nach der dritten, vierten bzw. funften Selektionsrunde betrugen die Anteile immuner Pflanzen (d.h. mit 0 Zysten) 1, 39 bzw. 50%. Das Inoculum von 16 Populationen aus ganz Neuseeland wurde an zwei resistente und zwei anfallige Weisskleelinien gegeben. Nach einer Generation der Nematodenentwicklung waren an den resistenten Linien bei jeder der untersuchten Populationen weniger Zysten. Die Reaktion von zwei resistenten und zwei anfalligen Linien auf einen Befall mit H. trifolii wurde in einem Gewachshausversuch gepruft. Der Befall verringerte das Sprossgewicht aller vier Linien, doch wuchsen die resistenten Linien nach 109, 126 und 160 Tagen besser als die beiden anfalligen Linien. Im Gegensatz dazu unterschieden sich die Linien bei Nichtbefall bei funf Probenahmen im Sprossgewicht nicht voneinander. An den anfalligen Pflanzen wurden mehr Zysten gefunden (im Mittel 370 und 430 je Pflanze) als an den resistenten Pflanzen (im Mittel 41 und 56 je Pflanze). Die Ergebnisse zeigen, dass die Entwicklung einer gegen H. trifolii resistenten Weisskleesorte erreichbar ist, und dass diese Resistenz gegen die Nematoden im grossten Teil Neuseelands wirksam sein wird. Die Wachstumsuntersuchungen haben gezeigt, dass die Vorteile besonders auf solchen Weideflachen deutlich werden, wo die Anwesenheit von H. trifolii erhebliche Einschrankungen des Wachstums und des Uberdauerns von Weissklee verursacht. [ABSTRACT FROM AUTHOR]

1. Dry matter yield, leaf growth and population dynamics of tunes taken from an old Lolium perenne/TrifoIium repens-dominated pasture were studied in controlled environment rooms at CO2 concentrations of 350μmol mol-1, 525 μmol mol-1 and 700 μmol mol-1 Starting with September data the turves were subjected sequentially to the mean monthly temperature and photoperiod taken from long-term climatic data for the area of New Zealand where the pasture was located. Each temperature and photoperiod regime was applied for 21 days to provide 12 different simulated 'months' of environmental conditions. The experiment ran for 14 simulated months. with September and October conditions being repeated at the end of the first simulated 'year'. Mean photon flux density throughout was 500 μE m-2s-1. The total quantity of herbage harvested was increased by 7% and 14% at 525 μmol mol-1 and 700 μmol mol-1 CO2, respectively. The increase in the amount of T. repens harvested by the end of the experiment was 63% at 525 μmol-1 mol-1 CO2, and 48% at 700 μmol-1 mol-1 CO2. In contrast, neither the yield of C3 grasses nor the yield of the only C4 grass present. Paspalum dilatatum, was significantly affected by CO2 concentration. The implications of this increase in the proportion of T. repens in temperate pastures at elevated CO2 is discussed briefly. 3. With the exception of a small increase in the specific leaf area of T. repens, detailed measurements of leaf growth on marked tillers (L. perenne and P. dilatatwn) and growing points (T. repens) showed no consistent effects of exposure to elevated CO2 concentrations. 4. Differences in yield between CO2 concentrations were mainly attributable to changes in the number and balance of population units. By the middle of the 'winter' conditions T. repens growing point densities at 700μmol mol-1 CO2 were more than double those found at 350μmol mol-1 but total grass tiller densities were unchanged. Growing point densities were also more than doubled at 525 μmol mol-1 CO2 compared with 350μmol mol-1 but grass tiller densities were reduced significantly below those recorded in the other two treatments. The relationship between the stability of herbage production and population densities is discussed and the potential interaction between population density, elevated CO2 and grazing considered. 5. Although exposure to elevated levels of CO2 did result in large changes in population numbers, this did not happen immediately and so the yield response of this particular community to CO2 varied with time. The average yield increases recorded here at elevated CO2 may therefore tend to underestimate those likely to be shown by communities that, at the population level, have become fully adapted to growth in a CO2-enriched atmosphere. [ABSTRACT FROM AUTHOR]

(1) The appearance and survival of Trifolium repens seedlings from naturally deposited seed were monitored for 3 years under different sheep grazing managements and phosphate fertilizer inputs, and in four slope aspect zones, in summer moist New Zealand hill country. (2) A mean of 5.5 seedlings m-2 per year appeared, representing 4.2% of the seeds deposited each summer. (3) Only 4.4% of seedlings survived to form established, stolon-bearing plants. representing a mean recruitment rate of one seedling per 5.5 m² per year. Survival was highest on steep north-west sites (10%), and nil on flat south-west sites, reflecting likely competitive stresses from surrounding vegetation. (4) Such low recruitment rates clearly indicate seedling regeneration plays only a minor role in T, repens persistence in this environment. Vegetative stolon densities of 3000 4000 m-2 and high rates of stolon initiation and death confirm that the species behaves essentially as a true perennial, (5) A useful ecological role for low seedling recruitment rates in maintaining genetic diversity within the T. repens population must be recognized, however, especially in highly variable environments. [ABSTRACT FROM AUTHOR]

(1) The appearance and fate (removal by livestock versus natural ripening and eventual seed deposition) of Trifolium repens flowerheads were measured for 3 years under different sheep grazing managements and soil fertility levels in a range of topographical (slope aspect) zones in summer-moist New Zealand hill country. (2) The spatial distribution of T. repens at the individual plant level (in 100 cm² quadrats) and thc treatment level were measured and related to flowerhead production. (3) Variation in flowerhead production between fertilizer levels largely paralleled variation in T. repens content of the sward, but there was a strong trend for greater flowering activity per unit of T. repens under rotational grazing than under set stocking. At the individual plant level, variation in density of T. repens foliage explained only 5 10% of the variation in numbers of flowerheads. Flowering appeared to be strongly influenced by micro-environment and genotype. (4) Removal of flowerheads, mostly unripe, by grazing stock was relatively consistent at 89-97% of flowerheads produced. On average, flowerheads were removed within 12 days of their appearance, with small treatment differences unlikely to influence thc viability of seed in consumed flowerheads. (5) Estimated seed yields were 275, 96 and 145 seeds m-2 (1.4, 0.5 and 0.8 kg ha-1) for the 3 years. 75% of which were hard seeds, Annual seed input depended much more on the number of flowerheads produced and the proportion of flowerheads grazed than on variation in yield per flowerhead. (6) Half-lives of buried seeds were estimated at about 1 year or less, with only 13% of seeds still surviving after 18 months in a simulated seed return experiment. High turnover rates in the buried seed pool indicate that seed reserves are likely to be relatively recent in origin and an ineffective source of new plants within existing swards. [ABSTRACT FROM AUTHOR]

(1) Elongation rates, node appearance rates and axillary bud development of Trifolium repens stolons in hill pastures were studied for 16 months under three grazing managements, viz, set stocked with sheep, rotationally grazed with sheep and rotationally grazed with cattle. Growth and survival of branch stolons and long-term survival of parent stolon material were also assessed. (2) Stolon elongation was greatest under cattle grazing; this difference between managements had both a genetic and environmental component. Node appearance rates, however, were similar under all managements. Stolon elongation, node appearance and axillary bud development occurred throughout the year but at varying rates depending on season. (3) The frequency of branch and adventitious root production per node was low and not widely different between managements. Frequencies were lowest in winter and highest in the first of two summers studied. Few inflorescences were formed per stolon. There was considerable variation within the sample in axillary bud development and rooting frequency. (4) On an area basis many branches are formed but their initial mortality is high. The large number of apical meristems (average c. 4000 m(&sup-2;)) ensures the maintenance of the population despite only a low proportion of potential branches developing. (5) Few stolon nodes or branches survived more than a year though branch stolon survival, elongation rates and node production were positively related to the occurrence of a root at the node of origin on the parent stolen. Node and branch death occurred continuously but at varying rates during the year. (6) Knowledge of the fate of axillary buds and the demography of nodes and apical meristems of T. repens is crucial to an understanding of the dynamics of the species and allows identification of specific plant breeding objectives for the improvement of T. repens contributions in grazed pastures. [ABSTRACT FROM AUTHOR]