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Keynote paper presented at the International Leucaena Conference, 1‒3 November 2018, Brisbane, Queensland, Australia.The perennial legume leucaena (Leucaena leucocephala) is grown across the subtropics for a variety of purposes including livestock fodder. Livestock in Australia emit a significant proportion of the methane produced by the agriculture sector and there is increasing pressure to decrease emissions from beef cattle production systems. In addition to direct productivity gains for livestock, leucaena has been shown to lower enteric methane production, suggesting an opportunity for emissions mitigation and Commonwealth Emissions Reduction Fund (ERF) methodology development, where leucaena browse is adopted for high value beef production. Determining the proportion of leucaena in the diet may be one of the more challenging aspects in attributing mitigation. Current enteric emission relationships for cattle consuming mixed grass-leucaena diets are based on intensive respiration chamber work. Herd-scale methane flux has also been determined using open path laser methodologies and may be used to validate an on-farm herd-scale methodology for leucaena feeding systems. The methodology should also address increased potential for soil organic carbon storage by leucaena grazing systems, and changes in nitrous oxide production. This paper outlines the background, justification, eligibility requirements and potential gaps in research for an emissions quantification protocol that will lead to the adoption of a leucaena methodology by the Australian beef industry. Development of a methodology would be supported by research conducted in Australia.

Soil nitrification (microbial oxidation of ammonium to nitrate) can lead to nitrogen leaching and environmental pollution. A number of plant species are able to suppress soil nitrifiers by exuding inhibitors from roots, a process called biological nitrification inhibition (BNI). However, the BNI activity of perennial grasses in the nutrient-poor soils of Australia and the effects of BNI activity on nitrifying microbes in the rhizosphere microbiome have not been well studied. Here we evaluated the BNI capacity of bermudagrass (Cynodon dactylon L.), St. Augustinegrass (Stenotaphrum secundatum (Walt.) Kuntze), saltwater couch (Sporobolus virginicus), seashore paspalum (Paspalum vaginatum Swartz.), and kikuyu grass (Pennisetum clandestinum) compared with the known positive control, koronivia grass (Brachiaria humidicola). The microbial communities were analysed by sequencing 16S rRNA genes. St. Augustinegrass and bermudagrass showed high BNI activity, about 80 to 90% of koronivia grass. All the three grasses with stronger BNI capacities suppressed the populations of Nitrospira in the rhizosphere, a bacteria genus with a nitrite-oxidizing function, but not all of the potential ammonia-oxidizing archaea. The rhizosphere of saltwater couch and seashore paspalum exerted a weak recruitment effect on the soil microbiome. Our results demonstrate that BNI activity of perennial grasses played a vital role in modulating nitrification-associated microbial populations.

Despite the popularity of bermudagrass (Cynodon dactylon L.) around the world, there are few studies that report genotypic and seasonal variation for sprouting of stolons used in pasture establishment or revegetation of disturbed land. This study investigated the genotypic/seasonal variation and the physiological basis of sprouting from nodes of aboveground stolons among 12 bermudagrasses. Sprouting percentage, total nodes per m (Nds), stolon diameter (SD), total aboveground biomass (TaB), and concentration of water soluble carbohydrate [WSC], concentration of starch [starch], concentration of non-structural carbohydrate [NSC], and concentration of crude protein [CP] were determined in different seasons including winter 2013, winter 2014, spring 2014, summer 2015, and fall 2015. Sprouting percentage for stolons sampled in spring and summer was higher than that for winter and fall. Large genotypic variation for sprouting was observed ranging from 44.1 to 80.2% of all nodes when averaged across seasons. Sprouting percentage among genotypes was strongly associated with SD, TaB, and Nds; and weakly associated with concentrations of photoassimilates such as [WSC], [starch], and [CP] in the aboveground biomass. However, when these photoassimilates were calculated as an amount per node, sprouting percentage was highly correlated with water soluble carbohydrate (WSC) (r = 0.80), crude protein (CP) (r = 0.82), and WSC + CP (r = 0.88). These data suggested that the size and/or maturity of the axillary buds at nodes and the available assimilate supply was underlying the sprouting potential of the bermudagrasses, however, more research under field conditions is required to validate this claim.

A research program to develop sterile leucaena has commenced to enhance red-meat production in additional regions of Australia including Western Australia, Northern Territory and New South Wales, where growing seeded leucaena is not currently permitted or encouraged. In this study we report on the development of methodology using a mutagenizing agent, EMS (ethyl methanesulfonate), to cause mutations in the self-fertile commercial leucaena cultivar, Redlands. Several experiments to determine the optimum rate of EMS have been completed and first generation mutagenized plants (M0) established in the field at Redlands Research Station, Cleveland, Queensland, Australia. An EMS concentration of 0.35% applied to germination paper proved the best method to achieve a target emergence percentage of 50%. To date, 27 of 179 mutagenized M0 seedless plants are considered to be putatively sterile. A further 1,200 M0 plants have been established in the field providing an even greater chance of identifying sterile leucaena plants with the desired forage quality and psyllid-resistance attributes. Resumen Un programa de investigación para desarrollar variedades de leucaena estériles fue iniciado para beneficiar la producción de carne roja en diferentes regiones de Australia, incluyendo Western Australia, Northern Territory y New South Wales, donde actualmente no se permite o fomenta el cultivo de leucaena por su potencial riesgo como maleza. En este estudio informamos sobre el desarrollo de una metodología utilizando un agente mutagenizante, EMS (metanosulfonato de etilo), para generar mutaciones en un cultivar comercial de leucaena autofértil, cv. Redlands. Se completaron varios experimentos para determinar la tasa óptima de EMS y se establecieron plantas mutagenizadas de primera generación (M0) en el campo de experimentación Redlands, Cleveland, Queensland, Australia. Se encontró que una concentración de EMS del 0.35% aplicado al papel de germinación es el mejor método para lograr un porcentaje de emergencia del 50%. Hasta la fecha, 27 de 179 plantas M0 mutagenizadas sin semillas se consideran supuestamente estériles. Se han establecido otras 1,200 plantas M0 en el campo, lo que brinda una posibilidad aún mayor de identificar plantas de leucaena estériles al tiempo que se retienen los atributos deseados como alta calidad forrajera y resistencia a los psílidos (insectos de la familia Psyllidae).

Water use and depth of water extraction of leucaena (Leucaena leucocephala) and Rhodes grass (Chloris gayana) pasture, irrigated with desalinated coal seam water (a by-product of the coal seam gas industry), were monitored to provide background information on root activity, spatial and temporal water use and deep drainage over a 757-day period from August 2011 to August 2013. Methodology comprised measurement of soil water from surface to 4 m depth using 8 EnviroSCAN probes connected to dataloggers positioned within leucaena twin rows and within the Rhodes grass inter-row. Just over 581,000 individual moisture measurements were collated and are reported here. Water extraction (and by inference root activity) of leucaena and Rhodes grass showed marked seasonal fluctuation with deepest and highest water extraction occurring during the first growing season; water extraction was greatly diminished during the following drier and cooler seasons due to the negative influences of lower soil moisture contents, lower temperatures and increased defoliation on pasture growth. The highest values of deep drainage below 4 m depth occurred when high rainfall events corresponded with high soil water storage in the entire profile (0–4 m depth). Given that water usage by both leucaena and Rhodes grass was greatest in the upper layers of soil (Keywords: Active rooting depth, agroforestry, Chloris gayana, Leucaena leucocephala, water extraction.DOI: 10.17138/TGFT(4)129-138

A large collection of over 1000 naturalised Australian bermudagrasses (Cynodon dactylon) was assembled. Previous research indicated that a subset of the grasses collected from Australian Mediterranean environments were drought resistant and characterised by large rhizomes that could be a potential source of nutrients, water and carbohydrates when these grasses grow under saline conditions. The objective of this research was to test the salinity tolerance of 12 bermudagrass genotypes with different levels of drought resistance using a flood and drain, sand-solution hydroponic system. Eight salt treatments were imposed ranging from 1.3 to 21 dS m-1 (corresponding 0 to 175 mM NaCl) for up to 17 weeks. Salinity tolerance among genotypes was categorised on the basis of 50% reduction in cumulative clipping yields, verdure and root biomass, and green cover, relative to the control treatment. There was no correlation between salt tolerance and drought resistance (r = -0.079 to 0.572), although some drought-resistant grasses did have excellent salt tolerance, such as entries MED1 and MED3. At 21 dS m-1, most grasses not only maintained over 50% total biomass but also retained over 70% green cover, relative to the control treatment, and were considered as highly salt tolerant. These salt-tolerant grasses have great potential for stabilising and revegetating saline and/or sodic soils.

Soil erosion and stabilisation are huge problems facing Australian land users, including those working in agriculture, mining, road construction and urban sports and community landscapes. There is a large opportunity for the Australian turfgrass industry to play a role in providing solutions to Australiafs land stabilisation issues. If 10% of these denuded landscapes can be vegetated by turfgrasses, the turfgrass industry as a whole can benefit greatly, particularly in the current economic climate, where the hangover from the global financial crisis has persisted. Collectively, the areas to be stabilised are enormous and to date the methods used to revegetate these land masses are limited. Hydrosprigging (HS) is an inexpensive, automated method of delivering grass sprigs (stolons) with a hydraulic pump to large areas of bare soil. In this study, we present our latest research on developing state-of-the-art HS methods. Significant differences for stolon sprouting of up to about 30% were identified among 12 bermudagrass genotypes harvested from the field. We hypothesise that the sprouting potential and vigour of shoots may be a function of the levels of nonstructural carbohydrate (NSC) present in the stolons at the time of planting. We also suggest that photothermal quotient, the ratio of solar radiation to temperature during the growing period, may provide the theoretical basis for predicting when levels of NSC may be optimum through the growing season.

Wear damage is one of the biggest problems associated with continuous use on sports and recreational turfgrass fields. Wear tolerance of 8 bermudagrass (Cynodon spp.) genotypes including 6 ecotypes collected from regional Australia and two commercial cultivars were evaluated in the field. Green cover after wear treatment of ecotypes 394 and MED3 was over 50% higher than the lowest genotypes. The wear tolerant genotypes also had significantly higher acid detergent fibre content, cellulose, lignin and total cell wall content than wear susceptible genotypes. Optical and scanning electron microscopies were used to study stolon and leaf transverse sections and leaf surface characteristics, respectively. Transverse sections of stolons and leaves, suggested that the fibre area surrounding vascular bundles of the wear tolerant genotypes was about 50% higher than the wear susceptible ones. Scanning electron micrographs of the leaf surface suggested that the arrangement of epidermal cells formed a ridged pattern. The gaps between the ridges of wear tolerant genotypes were shorter than those of the wear susceptible genotypes. Collectively, these results suggested that the mechanism of wear tolerance was associated with high fibre content in stolons and leaves. In addition, we suggest that the wear tolerant genotypes have a denser ridge pattern of epidermal cells probably giving the leaves greater tensile strength.

As a warm-season grass, bermudagrass (Cynodon spp.) has been widely used as turf and/or pasture in most parts of the world, however, frost is one of the most important factors to reduce growth and performance. Frost tolerance of 466 bermudagrass ecotypes collected from four climatic zones of Australia was assessed in a single field experiment in Southeast Queensland, Australia. In a second field experiment 12/466 ecotypes were assessed in a separate Southeast Queensland, location. Leaf death was scored after 7 frosts had occurred in each location over a 15-day period. For the evaluation of 466 entries, the ecotypes collected from regions with 30-40 and 40-50 potential frost days (PFD) based on 30-year climate data had over 50% lower leaf death than the ones from 0-10, 10-20 and 20-30 PFD. Ecotypes from the tropical rainy climatic zone had over 26% higher leaf death than the other climatic zones sampled in this study. In addition, there was a significant positive correlation between leaf death and plant height (r=0.84) and leaf death and clipping yield (r=0.96). The frost tolerance rating of 12/466 was validated at the second location. These results indicated that ecotypes from the geographic areas with longer period of PFD had superior frost tolerance. We suggest that the frost tolerant ecotypes were able to enter cold acclimation earlier than susceptible ones.

Climate change has brought a sharp and renewed focus on plant breeding programs to develop cultivars with improved performance in dry environments. The pleiotropic effects of selection for drought resistance are not well understood in perennial C 4 grasses. The objective of this study was to determine the commercial production characteristics including sod strength and post-harvest regrowth of bermudagrass ecotypes selected for drought resistance. These attributes were studied in a set of bermudagrasses ( Cynodon dactylon ), a species used extensively around the world for forage and turfgrass. Three field experiments using 12 genotypes contrasting for drought resistance were evaluated, on bermudagrass turf production facilities, for quality and regrowth after the canopy (sod) was mechanically removed. Among the genotypes tested, there was large genotypic variation for rhizome dry matter (RhDM) (0.01–0.81 kg m −2 ), aboveground dry matter (ADM) (0.59–0.17 kg m −2 ) and root dry matter (RDM) (0.04–0.12 kg m −2 ). Regrowth of the canopy was positively correlated to RhDM (r = 0.79∼0.80) and negatively correlated to ADM (r = −0.69∼−0.74) but there was no association with RDM. Biomass partitioning determined at the time of the second harvest revealed that genotypes with more rapid regrowth had larger proportional DM distributed to rhizome (63.5% vs 7.1%) than to aboveground (27.2% vs 86.5%) and root (8.5% vs 8.1%). Our previous research with these genotypes showed a strong correlation between drought resistance and RhDM prior to the drought period. Consequently, an analysis of the relationship between drought resistance measured previously and post-harvest regrowth in the experiments described here revealed a strong positive correlation (r > 0.64). Genotypic variation for sod strength, an important turf quality attribute, was large ranging from 1281 kg m −2 to 5671 kg m −2 . However, sod strength was neither correlated to drought resistance, nor the traits measured from harvested sod such as stolon diameter, internode length, number of branches and single stolon strength, nor to dry matter distribution. These results may reflect the existence of a range of different mechanisms for sod strength present in the material tested. Nevertheless, there were genotypes e.g., MED1 that combined the favorable traits of drought resistance, faster regrowth rate and higher sod strength and could be used as an important genetic resource for future breeding. MED1 was one of several highly rhizomatous genotypes in the study that originated from the Mediterranean climatic zone of Australia.

Although Setaria has been proposed as a model to investigate C4 photosynthesis, it may also be considered a suitable representative for biofuel feedstock species that are predominantly closely related panicoid grasses. In order to extend our understanding of the fundamental molecular and physiological mechanisms underpinning cell wall deposition as they occur during plant development, we have investigated an elongating stem internode of S. viridis. The chosen internode progressed from an active meristem and region of cell expansion at the base of the internode towards maturing fully expanded cells at the top of the internode. Along this developmental gradient, RNAseq of the mRNA fraction of the transcriptome was undertaken. A holistic understanding of the synthesis, composition and structure of the cell wall and the molecular mechanisms that signal the transition from primary to secondary cell wall synthesis will be integral to engineering crops with a structure that lends itself to more efficient deconstruction.

Dwarf cereal crops are widely grown world-wide because they offer productivity advantages to farmers, but the question of whether dwarfing genes change starch structure has not been examined. Starch properties, including digestion rate and mechanical properties of starch-containing biomaterials, are influenced by its structure, and thus significant changes might have health implications. Starch molecular structures of the grains from a semi-dwarf sd1 rice (Oryza sativa L.) mutant (Calrose 76) and its near-isogenic wild-type (Calrose) counterpart as well as of those from three dwarf sorghum (Sorghum bicolor L.) mutants and their near-isogenic tall revertants (due to the spontaneous reverse mutation of dw3 gene) were analyzed to understand the pleiotropic effects of dwarfing genes on starch biosynthesis in the grains. The structures of (fully branched) whole starch molecules and branch-chain length (from enzymatically debranched starch) were characterized using size-exclusion chromatography. The weight-average MW and radius of gyration of whole starch molecules were characterized using multiple-angle laser light scattering. There were no significant structural differences between each dwarf variety and its near-isogenic wild-type or tall revertant counterpart. Hence plant height reduction in rice and sorghum, controlled by the sd1 and dw3 genes, respectively, does not affect the biosynthesis of starch molecules in grains and is expected to have no significant impacts on starch crystalline and granular structures as well as starch functional properties, including its nutritional values.

Predictions of extreme weather resulting from climate change will present huge challenges for scientists trying to maintain and increase agricultural production. A greater frequency of dry periods is predicted placing emphasis on the development of plant varieties that are able to maintain performance in dry conditions. The aim of this research was to determine the genetic variation for drought resistance among a large range of potential pasture or turf bermudagrasses (Cynodon spp.). Four hundred and sixty genotypes including ecotypes collected from different climatic zones of Australia, and commercial cultivars were established in the field and assessed during natural and imposed drought periods. Using descriptors of drought resistance such as turf quality and green cover, genotypes were classified into different groups; 436 genotypes were clustered into ten groups in one experiment, and 72 genotypes were clustered into three groups in a second. There was a high correlation of response (r = 0.78) for 47 genotypes common to both experiments suggesting that the drought resistance techniques used to group genotypes were robust. Physiological analyses of the genotypes within the superior drought resistance groups indicated that these group members were probably able to extract more available soil water during the drought period. No commercial cultivars were found in the most drought resistance groups. These field studies also suggested that future collections of bermudagrass ecotypes designed to select for drought resistance might best be carried out from regions that experience Mediterranean climates. The field evaluations presented here did not correlate well with drought resistance determined in previously reported shallow lysimeter (40 cm deep) experiments.

The objectives of this paper were to (1) evaluate drought resistance of a large number of bermudagrass ecotypes collected from different climatic zones of regional Australia and compare their performance to commercial cultivars, (2) describe the mechanisms of drought resistance observed, and (3) investigate the relationship between geographic origins of the ecotypes and their drought resistance. Fifty-two genotypes of bermudagrass were evaluated in two field experiments using lysimeters 40 cm deep. The grasses were grown in well-watered conditions and then a drought treatment was imposed by withholding water and excluding rainfall using a portable rain-out shelter. Two criteria were used to select for drought resistance, i.e. survival period (SP), defined as the number of days after water was withheld to the stage when 100% leaf firing had occurred and Days 50 defined as the days required to reach 50% green cover. These experiments suggested that genotypes with superior drought resistance had lower stomatal conductance in the earlier phases of the dry-down period as suggested by less water use and higher canopy temperature depression. Lower water use during the early stage of dry-down resulted in more soil available water at the end of the drought period to extend green-leaf cover. There was no correlation between root dry matter and survival period/Days 50 . We also found some ecotypes performed better in drought conditions than popular commercial cultivars. There was no relationship between drought resistance and geographic origins, suggesting that drought resistant ecotypes could be obtained from any climatic zone sampled in this study.

Bermudagrasses (Cynodon spp.) are genetically and morphologically diverse warm-season species that are valuable for turf and forage. Diverse accessions of Cynodon are preserved in various germplasm banks in Asia, Europe, and the United States. However, the extent of genetic and ecological diversity within Australia has not been previously explored and characterized. To address this issue, a broad-scale collection of Cynodon germplasm across Australia was recently conducted. A core collection was generated from this resource to optimize its utilization in breeding and research. Genetic diversity of 690 Cynodon accessions was characterized using 16 expressed sequence tag (EST)-simple sequence repeat (SSR) markers. The mean number of alleles generated was 7.44 per marker. Genetic data was combined with passport, ploidy level, morphological, and experimental performance data to generate a core collection using a directed stratified sampling method. The core collection comprised 13% of the source germplasm and captured 96% of the allelic diversity. Redundancy within the core collection was avoided with all accessions representing unique genotypes. This core collection will facilitate the future use of Australian germplasm in Cynodon breeding, genomics, conservation, taxonomy, and phylogeographical research.

Self-fertility (SF) is an essential trait that contributes to yield stability in sunflower (Helianthus annuus L.), particularly in the absence of pollinating insects. We used a full-diallel design with 12 sunflower parents, including confectionary and nonconfectionary types, to assess (i) combining ability for SF, (ii) the relationship between SF and other traits, and (iii) microsatellite markers for tracking self-incompatible S alleles. Twelve parents and their 132 Fs were evaluated for SF in two environments. Self-fertility was correlated with final seed length (r = -0.57, P < 0.01), suggesting that SF was possibly influenced by floret characteristics. A genetic analysis of SF showed that both general combining ability (GCA) and specific combining ability (SCA) were significant, although after seed length was used as a covariate, the contribution of SCA effects increased to 65% of the variance and narrow-sense heritability was almost zero. The SCA effects were in part explained by the interaction of various combinations of S alleles. These results suggest that for programs targeting high-SF confectionary sunflower it would be difficult to predict the SF of hybrids based on the performance of their parents; therefore, F hybrid evaluation would be necessary. Our study suggested that factors controlling SF included GCA/SCA effects, S alleles, and floret characteristics. It also demonstrated the value of combining molecular and quantitative genetics for elucidating the inheritance of a complex trait.

Low temperature is a major abiotic stress for rice cultivation, causing serious yield loss in many countries. To identify QTL controlling low temperature induced spikelet sterility in rice, the progeny of F2, BC1F1 and BC2F1 populations derived from a Reiziq × Lijiangheigu cross were exposed to 21/15°C for 15 days at the booting stage, and spikelet sterility was assessed. For genotyping, 92 polymorphic markers from 373 SSR and 325 STS primer pairs were used. A major QTL was initially indentified on the short arm of chromosome 10 by selective genotyping using highly tolerant and susceptible progeny from F2 and BC1F1 populations. The QTL (qLTSPKST10.1) was validated and mapped by genotyping the entire F2 (282 progeny) and BC1F1 (84 progeny) populations. The results from the F2 population showed that qLTSPKST10.1 could explain 20.5% of the variation in spikelet sterility caused by low temperature treatment with additive (a = 14.4) and dominant effect (d = −7.5). From the analysis of 98 selected BC2F1 progeny, the QTL located in the 3.5 cM interval between S10010.9 and S10014.4 was further confirmed. Based on the studies of 3 generations in 2 years, it was clear that the QTL on chromosome 10 is a major determinant of the control of low temperature induced spikelet sterility at booting stage.

Leucaena (Leucaena leucocephala (Lam.) de Wit subsp. glabrata (Rose) Zarate) in combination with grass pasture is one of the most persistent, productive and sustainable grazing systems used in Queensland, Australia. Nevertheless, a better understanding of the competitive interactions that determine the proportions of leucaena and grass components is needed to optimise the design and management of the hedgerow pasture system. In a water-limited environment, belowground interactions between species are especially influential. Accordingly, the aim of this study was to determine the effect of leucaena plant density and Rhodes grass (Chloris gayana Kunth) competition on root distribution, evapotranspiration, patterns of soil-water use and the resulting water-use efficiency (WUE) of the leucaena and grass components. Results showed that although leucaena had deeper roots than Rhodes grass, the majority of fine roots of both leucaena and Rhodes grass were in the upper 1.5 m of the soil profile suggesting a high level of competition for water resources. A major factor favouring Rhodes grass was that its root abundance was 8–10 times greater than leucaena, allowing it to compete more effectively for water resources and limit the lateral spread of leucaena roots. Higher cumulative evapotranspiration values were recorded from leucaena grown with Rhodes grass than from leucaena grown in absence of grass. However, this difference was negligible at the highest leucaena density owing to the reduced yield of grass caused by shading and increased water uptake of leucaena. The findings of this study also confirmed the hypothesis that at low tree densities, leucaena–grass pasture will have higher WUE (13.8 kg DM mm–1) than sole leucaena, but this difference was reduced with increments of leucaena density. Highest WUE (65.9 kg DM mm–1) occurred at highest leucaena density with or without grass.

Silvopastoral systems with the tree legume leucaena (Leucaena leucocephala (Lam.) de Wit) and grass pastures are widely used for ruminant feeding in subtropical and tropical regions. Different densities and planting configurations of leucaena will influence relative yields of both species because of intra- and interspecific competition. With the aim to describe the effects of competition between leucaena and Rhodes grass (Chloris gayana Kunth), a Nelder Wheel trial with 10 different leucaena tree densities (100–80 000 trees ha–1) growing with and without Rhodes grass was established in a subtropical environment at Gatton, south-east Queensland, in November 2013. From 2014 to 2016, the biomass of leucaena (six harvests) and Rhodes grass (seven harvests) was measured by using allometric equations and the BOTANAL sampling procedure over 742 and 721 days, respectively. No complementary or facilitative aboveground interactions were observed between the leucaena and Rhodes grass components of the pasture system. Increasing leucaena tree density resulted in greater aboveground intra- and interspecific competition. Average maximum individual tree yield (38.9 kg DM tree–1 year–1) was reached at 100 trees ha–1 without grass competition and was reduced by 60% with grass competition. Rhodes grass biomass yield was negatively affected by shading from the leucaena canopy, with negligible grass yield at tree densities ≥8618 trees ha–1. Therefore, there was effectively no grass competition on individual tree yield at higher leucaena densities. Accordingly, edible leucaena biomass per unit area was positively related to log10 leucaena density (R2 = 0.99) regardless of grass competition, reaching 21.7 t DM ha–1 year–1 (2014–15) and 27 t DM ha–1 year–1 (2015–16) at the highest leucaena density of 80 000 trees ha–1. By contrast, the yield of Rhodes grass was linearly and inversely correlated with log10 tree density (R2 = 0.99). Practical implications for the design and management of commercial leucaena–grass pastures are discussed.

Water use in both urban and rural communities has become an enormous environmental and social issue, and over 30% of domestic water consumption is applied outdoors. To use Australia's unique biodiversity to select turfgrasses that maintain quality with reduced inputs of water and nutrients, we have collected about 500 indigenous couch grass genotypes and have begun to characterise them using physiological and genomics tools. Here we report on experiments that aim to develop the methodologies for screening a large number of genotypes for water use efficiency. Eight Cynodon grasses were grown in 40-cm-long PVC tubes with two soil types, two cutting heights, and four replications. The plants were grown at field capacity for several weeks prior to applying a terminal water stress. A survival period was estimated based on the time from the last watering to the time that all green leaf was lost. Large genotypic differences in survival period of up to 14 days were observed. Two genotypes, '81-1' and 'CT2', outperformed the other genotypes for survival period, possibly due to lower rates of evapotranspiration either through lower stomatal conductance and/or lower leaf area.

Weather damage reduces the value of commercial mungbean. but hard-seededness can reduce the level of damage. However. attempts lo breed large- and hard-seeded mungbean varieties have been unsuccessful. To understand the relationship between seed weight and hard-seededness. these trails were investigated using a quantitative trail loci (QTL) mapping approach with a recombinant inbred population derived from a cross between a completely soft-seeded variety and a completely hard-seeded genotype. The two parental genotypes also had a sixfold difference in seed weight. QTL analyses revealed four loci for hard-seededness and 11 loci for seed weight. Two of the hard-seeded ness loci co-localized with seed weight QTL. When seed weight was used as a covariate in the analysis of hard-seededness from the field data, two of the four hard-seeded QTL remained significant with the effect al one of these remaining unchanged. These results explain why retaining hard-seededness in large seeded mungbean lines has been unsuccessful. The existence of a persistent locus, however. indicated that breeding large and persistently hard-seeded varieties of mungbean may be possible.

pleted, followed by 2 cycles of progeny testing and se-lection for self-compatibility to achieve stability and uni-formity (2009−2012). Forty elite psyllid-resistant lines were then evaluated to identify the most suitable lines for release to industry. This paper describes the results of these trials.

Bacterial artificial chromosome (BAC) libraries have been widely used in different aspects of genome research. In this paper we report the construction of the first mungbean (Vigna radiata L. Wilczek) BAC libraries. These BAC clones were obtained from two ligations and represent an estimated 3.5 genome equivalents. This correlated well with the screening of nine random single-copy restriction fragment length polymorphism probes, which detected on average three BACs each. These mungbean clones were successfully used in the development of two PCR-based markers linked closely with a major locus conditioning bruchid (Callosobruchus chinesis) resistance. These markers will be invaluable in facilitating the introgression of bruchid resistance into breeding programmes as well as the further characterisation of the resistance locus.

Plants accumulate isotopes of carbon at different rates because of discrimination against C-13 relative to C-12. In plants that fix carbon by the C-3 pathway, the amount of discrimination correlates negatively with transpiration efficiency (TE) where TE is the amount of dry matter accumulated per unit water transpired. Therefore, carbon isotope discrimination (Delta) has become a useful tool for selecting genotypes with improved TE and performance in dry environments. Surveys of 161 sunflower (Helianthus spp.) genotypes of diverse origin revealed a large and unprecedented range of genetic variation for Delta (19.5-23.8parts per thousand). A strong negative genetic correlation (r(g)) between TE and Delta (r(g) = -0.87, P < 0.001) was observed in glasshouse studies. Gas exchange measurements of field grown plants indicated that Delta was strongly correlated with stomatal conductance to water vapor (g), (r(g) 0.64, P < 0.01), and the ratio of net assimilation rate (A) to g, (r(g) = 0.86, P < 0.001), an instantaneous measure of TE. Genotype CMSHA89MAX1 had the lowest TE (and highest Delta) of all genotypes tested in these studies and low yields in hybrid combination. Backcrossing studies showed that the TE of this genotype was due to an adverse effect of the MAX1 cytoplasm, which was inherited from the diploid perennial H. maximiliani Schrader. Overall, these studies suggested that there is an excellent opportunity for breeders to develop sunflower germplasm with improved TE. This can be achieved, in part, by avoiding cytoplasms such as the MAX1 cytoplasm.

Previously, we showed that genotypic differences in soil water extraction were associated with drought response, but we did not study underground root and rhizome characteristics. In this study, we demonstrate a similar relationship between drought resistance and soil water extraction but investigate the role of underground organs. Eighteen bermudagrass genotypes (Cynodon spp.) from four climatic zones were assessed under continuous drought at two locations with contrasting soils and climates. The criterion for drought resistance was the duration required to reach 50% green cover (GC50) after water was withheld. GC50, physiological traits, rhizome dry matter (RhDM), root length density (RLD) and average root diameter (ARD) were determined in both locations; water extraction was measured in one location. Large genotypic variation for drought resistance was observed in both locations, with GC50 being 187-277 days in a clay soil and 15-27 days in a sandy soil. Drought-resistant genotypes had greater soil water extraction and a higher water uptake rate. GC50 was correlated with relative water content (r=0.76), canopy temperature differential (r=-0.94) and photosynthetic rate (r=0.87) measured during drought; RhDM (r=0.78 to ~0.93) before and after drought; and ARD after drought (r=0.82 to ~0.94); GC50 was not correlated with RLD. Ecotypes collected from the Australian Mediterranean zone had superior drought resistance and were characterised by a large rhizome network. This is the first comprehensive study with perennial C4 grasses describing the association between water extraction, root distribution, rhizomes and drought resistance.

The objective of this study was to investigate patterns of soil water extraction and drought resistance among genotypes of bermudagrass (Cynodon spp.) a perennial C4 grass. Four wild Australian ecotypes (1-1, 25a1, 40-1, and 81-1) and four cultivars (CT2, Grand Prix, Legend, and Wintergreen) were examined in field experiments with rainfall excluded to monitor soil water extraction at 30-190cm depths. In the study we defined drought resistance as the ability to maintain green canopy cover under drought. The most drought resistant genotypes (40-1 and 25a1) maintained more green cover (55-85% vs 5-10%) during water deficit and extracted more soil water (120-160mm vs 77-107mm) than drought sensitive genotypes, especially at depths from 50 to 110cm, though all genotypes extracted water to 190cm. The maintenance of green cover and higher soil water extraction were associated with higher stomatal conductance, photosynthetic rate and relative water content. For all genotypes, the pattern of water use as a percentage of total water use was similar across depth and time We propose the observed genetic variation was related to different root characteristics (root length density, hydraulic conductivity, root activity) although shoot sensitivity to drying soil cannot be ruled out.

Cynodon L. C. Rich comprises warm season grass species that are valuable as turf and forage in warm climates across the globe. Traditionally, Cynodon breeding programs have aimed to produce varieties with improved turf and forage grass quality characteristics. More recent goals, such as improved abiotic stress tolerance, aim to address challenges associated with climate change. Germplasm collections representing a fraction of the global distribution of Cynodon comprise the plant resource for these breeding programs. We compared a core collection consisting of 116 Australian genotypes with an international core collection of 59 genotypes representing Cynodon’s global distribution. Our aims were to determine whether unique genetic diversity exists amongst Australian Cynodon that may enhance international breeding resources. This research will facilitate the incorporation of Australian Cynodon genetic resources, which have expanded and naturalized under harsh Australian climates, into existing germplasm collections.

Sunflower rust, Incited by Puccinia helianthi Schw., is a significant disease problem in sunflower (Helianthus annuus L.) production areas of North America, Argentina, and Australia and has been identified on sunflower grown in all regions of the world. Five races of rust presently have been identified in the USA. Recently, a new rust isolate gave a previously unreported virulence reaction pattern and was designated North American Race 6. A genetic study was conducted to determine the inheritance of resistance to Race 6 found in MC29 (AUS), a germplasm line introduced from Australia. F-1, F-2, and testcross progeny were produced from two crosses following hand pollinations: HA89/MC29 (AUS) and MC29 (AUS)/MC69. A multiple race inoculation technique was utilized under greenhouse conditions to evaluate the resistance or susceptibility of each plant to North American Races 1, 3, and 6. Chi-square tests for goodness of fit and heterogeneity were utilized to test each Fz and testcross family. A single, dominant gene in MC29 (AUS) was found to confer resistance to North American Races 1, 3, and 6. The gene was independent and nonallelic to the genes R(1) and R(2), and was designated R(10). Identification of resistance to Race 6 has increased the genetic diversity of resistance to sunflower rust in North America.

Cynodon species are multiple-use grasses that display varying levels of adaptation to biotic and abiotic stress. Previously identified EST-SSR primers were characterized and multiplexed to assess the level of genetic diversity present within a collection of almost 1200 Cynodon accessions from across Australia. •Two multiplex reactions were developed comprising a total of 16 EST-SSR markers. All SSR markers amplified across different Cynodon species and different levels of ploidy. The number of alleles ranged from one to eight per locus and the total number of alleles for the germplasm collection was 79. •The 16 markers show sufficient variation for the characterization of Cynodon core collections and analysis of population genetic diversity in Cynodon grasses.

There is currently a growing coal seam gas (CSG) industry in Queensland, Australia. The industry requires beneficialuse strategies to consume the significant volumes of water released during CSG extraction. Irrigation of tropical and subtropical forage species for beef production is one option; however, quality of coal seam (CS) water varies due to moderate–high salinity and alkalinity. The application of chemically amended CS water over time could potentially increase soil salinity, which is known to reduce plant biomass production (Shabala and Munns 2012). While the salinity tolerance of many tropical and subtropical forage species has been investigated over the last 30 years (Russell 1976; Keating et al. 1986; Kitamura 1986; Hansen and Munns 1988; Deifel et al. 2006), there is a need to examine the tolerance of more recently released species and cultivars, which are suitable for planting in the Queensland CSG area.

Previously, we showed that genotypic differences in soil water extraction were associated with drought response, but we did not study underground root and rhizome characteristics. In this study, we demonstrate a similar relationship between drought resistance and soil water extraction but investigate the role of underground organs. Eighteen bermudagrass genotypes (Cynodon spp.) from four climatic zones were assessed under continuous drought at two locations with contrasting soils and climates. The criterion for drought resistance was the duration required to reach 50% green cover (GC50) after water was withheld. GC50, physiological traits, rhizome dry matter (RhDM), root length density (RLD) and average root diameter (ARD) were determined in both locations; water extraction was measured in one location. Large genotypic variation for drought resistance was observed in both locations, with GC50 being 187–277 days in a clay soil and 15–27 days in a sandy soil. Drought-resistant genotypes had greater soil water extraction and a higher water uptake rate. GC50 was correlated with relative water content (r = 0.76), canopy temperature differential (r = –0.94) and photosynthetic rate (r = 0.87) measured during drought; RhDM (r = 0.78 to ~0.93) before and after drought; and ARD after drought (r = 0.82 to ~0.94); GC50 was not correlated with RLD. Ecotypes collected from the Australian Mediterranean zone had superior drought resistance and were characterised by a large rhizome network. This is the first comprehensive study with perennial C4 grasses describing the association between water extraction, root distribution, rhizomes and drought resistance.

A genetic linkage map of mungbean ( Vigna radiata, 2n = 2 x = 22) consisting of 255 RFLP loci was developed using a recombinant inbred population of 80 individuals. The population was derived from an inter-subspecific cross between the cultivated mungbean variety 'Berken' and a wild mungbean genotype 'ACC 41' ( V. radiata subsp. sublobata). The total length of the map, which comprised 13 linkage groups, spanned 737.9 cM with an average distance between markers of 3.0 cM and a maximum distance between linked markers of 15.4 cM. The mungbean map was compared to a previously published map of lablab ( Lablab purpureus, 2n = 2 x = 24) using a common set of 65 RFLP probes. In contrast to some other comparative mapping studies among members of the Fabaceae, where a high level of chromosomal rearrangement has been observed, marker order between mungbean and lablab was found to be highly conserved. However, the two genomes have apparently accumulated a large number of duplications/deletions after they diverged.

The objective of this study was to investigate patterns of soil water extraction and drought resistance among genotypes of bermudagrass (Cynodon spp.) a perennial C4 grass. Four wild Australian ecotypes (1–1, 25a1, 40–1, and 81–1) and four cultivars (CT2, Grand Prix, Legend, and Wintergreen) were examined in field experiments with rainfall excluded to monitor soil water extraction at 30–190 cm depths. In the study we defined drought resistance as the ability to maintain green canopy cover under drought. The most drought resistant genotypes (40–1 and 25a1) maintained more green cover (55–85% vs 5–10%) during water deficit and extracted more soil water (120–160 mm vs 77–107 mm) than drought sensitive genotypes, especially at depths from 50 to 110 cm, though all genotypes extracted water to 190 cm. The maintenance of green cover and higher soil water extraction were associated with higher stomatal conductance, photosynthetic rate and relative water content. For all genotypes, the pattern of water use as a percentage of total water use was similar across depth and time We propose the observed genetic variation was related to different root characteristics (root length density, hydraulic conductivity, root activity) although shoot sensitivity to drying soil cannot be ruled out.

The effect of temperature upon plant growth and partitioning of dry matter in sugarcane (Saccharum spp.) was determined. Sugarcane plants of two commercial cultivars, Q117 and Q138 were grown under constant conditions for 72 days then subjected to one of four different ambient temperature regimes, 14, 18, 22 or 26°C. Plants were harvested before the imposition of the treatments, then at 85, 120, 155 and 190 days after planting (DAP) for biomass and sugar partitioning. Following the imposition of temperature treatments, the increase in stalk length and node number was linear and notably different between the temperature regimes for both cultivars. When the data was described in terms of thermal time (growth temperature (°C) × number of days), the number of internodes produced per unit of thermal time was the same irrespective of the temperature in which the plants were grown and internode number increased in a linear manner with an increase in total thermal input. Stalk dry matter accumulation over time was linear at the log-scale and highly significant, (P

Increasing demand for scarce water resources in Australia has led to the selection of turfgrass genotypes with good drought tolerance. Here we describe the development of methodologies for screening green couch grasses (Cynodon spp.) grown in 40-cm PVC pots placed under rainout shelters. The drought tolerance of up to 8 genotypes including 4 commercial varieties (CT2, Grand Prix, Legend, and Winter Green) and 4 wild Australian ecotypes (1-1, 25-a-1, 40-1, and 81-1) was examined in 3 experiments conducted in 2007–08 and 2008–09. In the first experiment, all genotypes were grown with 2 soil types (clay and sandy soils) and 2 clipping heights (5 and 2 cm). Genotypic variation for survival period (defined as the period from the time water was withheld until 100% leaf firing had occurred) was high for the sandy soil × 2 cm clipping height treatment and, because retrieval of roots was easy, this combination was used in Expts 2 and 3 as the best system for screening drought tolerance. This method gave highly repeatable results across 2 years. Wild ecotype 81-1 had a significantly longer survival period than other genotypes, possibly associated with lower stomatal conductance early after water deficit was imposed, a greater root biomass at depth, and greater osmotic adjustment.

Twenty-six mungbean varieties and accessions were screened for resistance to 4 bruchid species (Coleoptera : Chrysomelidae). On the basis of the percentage of seeds damaged all Australian commercial mungbean varieties tested here were highly susceptible to strains of Callosobruchus maculatus and C. chinensis, the 2 species that cause most damage worldwide to mungbean in storage. In addition, 3 accessions of wild mungbean appeared to have bruchid resistance. The texture layer present on the seed coat of some mungbean varieties and small seed size may act as oviposition deterrents. Consequently, these assays for determining resistance to bruchid infestation may not be suitable for identifying biochemical resistance of some mungbean genotypes.

Two genetic linkage maps of mungbean derived from the cross Berken ACC 41 are reported. The F2 map constructed from 67 individuals consisted of 110 markers (52 RFLP and 56 RAPD) that grouped into 12 linkage groups. The linked markers spanned a total map distance of 758.3 cM. A recombinant inbred (RI) population derived from the 67 F2 individuals was used for the generation of an additional linkage map. The RI map, composed entirely of RAPD markers, consisted of 115 markers in 12 linkage groups. The linked markers spanned a total map distance of 691.7 cM. Using a framework set of RFLP markers, the F2 map was compared with another F2 mungbean map constructed in Minnesota. In general, the order of these markers was consistent between maps. Segregation distortion was observed for some markers. 14.5% (16/110) of mapped F2 markers and 24% (28/115) of mapped RI markers segregated with distorted ratios. Segregation distortion occurred in each successive generation after the F2 . The regions of distortion identified in the Australian maps did not coincide with regions of the Minnesota map.

The position of Australian accessions of wild mungbean (Vigna radiata ssp. sublobata) in the Asiatic Vigna gene pool was examined by assessing their cross fertility with the green gram cultigen (Vigna radiata ssp. radiata) and black gram (Vigna mungo). No difficulties were encountered in obtaining F 1 and backcross seed in crosses with green gram. The hybrid progenies were vegetatively vigorous and fully fertile. Inheritance of traits appeared normal and, where direct comparisons were possible, consistent with crosses within the cultigen. Inheritance of a new seed mottling gene is presented and several linked traits were found. Crosses with black gram proved difficult to achieve, and the resulting hybrid seed showed varying degrees of viability. Individuals that germinated were weak, and if they survived to flower, possessed low pollen fertility and poor seed set. It was concluded that indigenous Australian accessions of wild mungbean belong to the primary gene pool of Vigna radiata.