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The present study aimed to investigate the effect of defoliation frequency (low and high) and water stress (excess or deficit) on biomass production, P and N nutrition, and symbiosis with native soil microorganisms on a Lotus tenuis and Schedonorus arundinaceus co-culture in a pot experiment. Combined effects of defoliation frequency and water stress affected plant accumulated shoot biomass. L. tenuis root biomass decreased in response to defoliation and water stress, while S. arundinaceus root biomass was similar between non-defoliated and defoliated plants, at all water levels. Low and high frequencies of defoliation in a waterlogged soil can be considered the most stressful scenario for L. tenuis and S. arundinaceus co-culture. Colonization of arbuscular mycorrhizal fungi in L. tenuis roots and dark septate endophytes colonization in S. arundinaceus roots were affected by both factors, whereas arbuscular mycorrhizal colonization in S. arundinaceus was affected only by water stress. Both plants tolerated defoliation and water stress due to the interaction between the translocation of nutrients and carbon compounds from roots to shoots, and P and N absorption (plus N2 fixation in L. tenuis). [ABSTRACT FROM AUTHOR]

Root fungal endophytes are essential mediators of plant nutrition under mild stress conditions. However, variations in the rhizosphere environment, such as nutrient depletion, could result in a stressful situation for both partners, shifting mutualistic to nonconvenient interactions. Mycorrhizal fungi and dark septate endophytes (DSEs) have demonstrated their ability to facilitate phosphate (Pi) acquisition. However, few studies have investigated other plant–fungal interactions that take place in the root environment with regard to phosphate nutrition. In the present research work, we aimed to analyze the effect of extreme Pi starvation and the fungal endophyte Fusarium solani on the model Lotus japonicus and the crop L. tenuis. We conducted metabolomics analysis based on gas chromatography-mass spectrometry (GC-MS) on plant tissues under optimal conditions, severe Pi starvation and F.solani presence. By combining statistical and correlation network analysis strategies, we demonstrated the differential outcomes of the two plant species against the combination of treatments. The combination of nutritional stress and Fusarium presence activated significant modifications in the metabolism of L. japonicus affecting the levels of sugars, polyols and some amino acids. Our results display potential markers for further inspection of the factors related to plant nutrition and plant–fungal interactions. [ABSTRACT FROM AUTHOR]

Promoting the forage Lotus tenuis is an appealing alternative to meet the needs for cattle production in the Flooding Pampa region, Argentina. This agricultural practice requires herbicides application to remove plant species competing with L. tenuis . The use of chemical compounds, in addition to the removal of native vegetation, eventually may change the diversity of other ecosystem components such as bacterial communities. The objectives of this work were to examine the effect of L. tenuis promotion on the bacterial community composition and on specific water-related soil variables, and to detect specific bacterial taxa responding to the L. tenuis promotion. In order to achieve these objectives, here we studied three different rangeland sites of the Flooding Pampa region. At each site, two paddocks were compared, one managed to promote the forage legume L. tenuis , and the other lacking of management history and hence, covered by natural grasses. To asses bacterial diversity we used 454-FLX pyrosequencing technology of the V4 region of the 16S rRNA gene, on genomic DNA extracted from soil samples. We obtained 135.918 sequences, representing 3187 Operational Taxonomic Units (OTUs) distributed in 12 phyla and 45 classes. Overall, the main identified components of the bacterial community at the Phylum level were Acidobacteria, followed by Verrucomicrobia, Planctomycetes and Chloroflexi. Our results suggest that 5-6 years of land use with L. tenuis promotion does not affect the microbial community structure in this ecosystem. NMDS ordination in two dimensions based on Bray–Curtis distances and PERMANOVA test did not show differences in bacterial community composition between paddocks promoted or not with L. tenuis, although differences among sites were detected. In parallel, Pearson’s correlation analysis suggested that L. tenuis promotion would indirectly affect members of classes Acidobacteria and Anaerolineae, through altering water-related soil properties. [ABSTRACT FROM AUTHOR]

Soil alkalinity is one of the most serious agricultural problems limiting crop yields. The legume Lotus tenuis is an important forage acknowledged by its ability to naturally grow in alkaline soils. To gain insight into the molecular responses that are activated by alkalinity in L. tenuis plants, subtractive cDNA libraries were generated from leaves and roots of these plants. Total RNAs of non-stressed plants (pH 5.8; E.C. 1.2), and plants stressed by the addition of 10 mM of NaHCO3 (pH 9.0; E.C. 1.9), were used as source of the driver and the tester samples, respectively. RNA samples were collected after 14 and 28 days of treatment. A total of 158 unigenes from leaves and 92 unigenes from roots were obtained and classified into 11 functional categories. Unigenes from these categories (4 for leaves and 8 for roots), that were related with nutrient metabolism and oxidative stress relief were selected, and their differential expression analyzed by qRT-PCR. These genes were found to be differentially expressed in a time dependent manner in L. tenuis during the alkaline stress application. Data generated from this study will contribute to the understanding of the general molecular mechanisms associated to plant tolerance under long-term alkaline stress in plants. [ABSTRACT FROM AUTHOR]

Highlights: [•] Lotus seedlings are highly tolerant to water stress from deficit to waterlogging. [•] Lotus seedlings tolerate salinity and regulate Na+ concentration in tissue. [•] Lotus establishes early associations with AM fungi and Rhizobium. [•] Lotus seedlings acquire early imprints to respond better to future stress episodes. [Copyright &y& Elsevier]

Mesorhizobium loti MAFF303099 has a functional type III secretory system ( T3SS) involved in the nodulation process on Lotus tenuis and Lotus japonicus. Four putative M. loti T3SS effectors ( Mlr6358, Mlr6331, Mlr6361, and Mlr6316) have been previously described, and it has been demonstrated that the N-terminal regions of Mlr6361 and Mlr6358 mediate the secretion via a T3SS. Here, we demonstrate the capacity of Mlr6316 and Mlr6331 N-terminal regions to direct the secretion of a translational fusion to a reporter peptide through T3SS. By using single, double, and triple mutants, we demonstrated the positive and negative participation of some of these proteins in the determination of competitiveness on Lotus spp. Low competitiveness values correlated with low nodulation efficiency for a mutant deficient in three of the putative M. loti effectors. Our data suggest that the net effect of M. loti T3SS function on symbiotic process with Lotus results from a balance between positive and negative effects. [ABSTRACT FROM AUTHOR]

Biomass and plant density of Lotus tenuis Waldst. & Kit. ex Willd. have been reported in decreasing in grasslands and pastures. Our objective was to determine if L. tenuis biomass and plant density can be increased in grassland through seed addition. Two separated experiments under cattle grazing exclusion were conducted in three paddocks of a Flooding Pampa grassland. The first experiment was from autumn 2004 to autumn 2006 and the second from autumn 2005 to autumn 2007. Different L. tenuis seed additions (0, 57, 229, 917 and 1833 seeds m-2) were broadcast into experimental plots. In the second experiment, besides seed additions there was a reseeding of approximately 900 seed m-2 from seed rain produced by plants of grassland. Seed density explained the 81% and 19% of the variation in seedling density and L. tenuis biomass, respectively. Seedling emergence occurred mainly between autumn and early spring, while seedling mortality was mainly between late spring and early summer. Lotus tenuis adult plant density and biomass production increased with seed additions. Total biomass production in the plant community varied between 589.94 ± 26.89 and 1042.44 ± 54.39 g m-2 yr-1 and the differences were principally attributed to precipitations. Lotus tenuis biomass contribution was of approximately 10%. The results suggest that L. tenuis seedling and plant establishment and biomass production can be increased through seed addition and/or seed rain through grazing exclusion during reproductive period. [ABSTRACT FROM AUTHOR]

Salinity and waterlogging interact to reduce growth for most crop and pasture species. The combination of these stresses often cause a large increase in the rate of Na+ and Cl− transport to shoots; however, the mechanisms responsible for this are largely unknown. To identify mechanisms contributing to the adverse interaction between salinity and waterlogging, we compared two Lotus species with contrasting tolerances when grown under saline (200 m M NaCl) and O2-deficient (stagnant) treatments. Measurements of radial O2 loss (ROL) under stagnant conditions indicated that more O2 reaches root tips of Lotus tenuis, compared with Lotus corniculatus. Better internal aeration would contribute to maintaining Na+ and Cl− transport processes in roots of L. tenuis exposed to stagnant-plus-NaCl treatments. L. tenuis root Na+ concentrations after stagnant-plus-NaCl treatment (200 m M) were 17% higher than L. corniculatus, with 55% of the total plant Na+ being accumulated in roots, compared with only 39% for L. corniculatus. L. tenuis accumulated more Na+ in roots, presumably in vacuoles, thereby reducing transport to the shoot (25% lower than L. corniculatus). A candidate gene for vacuole Na+ accumulation, an NHX1-like gene, was cloned from L. tenuis and identity established via sequencing and yeast complementation. Transcript levels of NHX1 in L. tenuis roots under stagnant-plus-NaCl treatment were the same as for aerated NaCl, whereas L. corniculatus roots had reduced transcript levels. Enhanced O2 transport to roots enables regulation of Na+ transport processes in L. tenuis roots, contributing to tolerance to combined salinity and waterlogging stresses. [ABSTRACT FROM AUTHOR]

Background and Aims: Two main strategies that allow plants to cope with soil waterlogging or deeper submergence are: (1) escaping by means of upward shoot elongation or (2) remaining quiescent underwater. This study investigates these strategies in Lotus tenuis, a forage legume of increasing importance in areas prone to soil waterlogging, shallow submergence or complete submergence. [ABSTRACT FROM PUBLISHER]

A total of 103 root nodule isolates were used to estimate the diversity of bacteria nodulating Lotus tenuis in typical soils of the Salado River Basin. A high level of genetic diversity was revealed by repetitive extragenic palindromic PCR, and 77 isolates with unique genomic fingerprints were further differentiated into two clusters, clusters A and B, after 16S rRNA restriction fragment length polymorphism analysis. Cluster A strains appeared to be related to the genus Mesorhizobium, whereas cluster B was related to the genus Rhizobium. 16S rRNA sequence and phylogenetic analysis further supported the distribution of most of the symbiotic isolates in either Rhizobium or Mesorhizobium: the only exception was isolate BA135, whose 16S rRNA gene was closely related to the 16S rRNA gene of the genus Aminobacter. Most Mesorhizobium-like isolates were closely related to Mesorhizobium amorphae, Mesorhizobium mediterraneum, Mesorhizobium tianshanense, or the broad-host-range strain NZP2037, but surprisingly few isolates grouped with Mesorhizobium loti type strain NZP2213. Rhizobium-like strains were related to Rhizobium gallicum, Rhizobium etli,or Rhizobium tropici, for which Phaseolus vulgaris is a common host. However, no nodC or nifH genes could be amplified from the L. tenuis isolates, suggesting that they have rather divergent symbiosis genes. In contrast, nodC genes from the Mesorhizobium and Aminobacter strains were closely related to nodC genes from narrow-host-range M. loti strains. Likewise, nifH gene sequences were very highly conserved among the Argentinian isolates and reference Lotus rhizobia. The high levels of conservation of the nodC and nifH genes suggest that there was a common origin of the symbiosis genes in narrow-host-range Lotus symbionts, supporting the hypothesis that both intrageneric horizontal gene transfer and intergeneric horizontal gene transfer are important mechanisms for the spread of symbiotic capacity in the Salado River Basin. [ABSTRACT FROM AUTHOR]

The impact of deficit and excess of soil water on plant growth, morphological plant features, N and P plant nutrition, soil properties, Rhizobium nodulation and the symbiosis between arbuscular mycorrhizal (AM) fungi and Lotus tenuis Waldst. & Kit. were studied in a saline-sodic soil. Water excess treatment decreased root growth by 36% and increased shoot growth by 13% whereas water deficit treatment decreased both root and shoot growth (26 and 32%, respectively). Differences between stress conditions on shoot growth were due to the ability of L. tenuis to tolerate low oxygen concentration in the soil and the sufficiency of nutrients in soil to sustain shoot growth demands. Water excess treatment decreased pH, and increased available P and labile C in soil. Water deficit treatment decreased available P and also increased labile C. In general, N and P acquisition were affected more by water excess than water deficit. The number of nodules per gram of fresh roots only increased in water excess roots (97%). Under both stress conditions there was a significant proportion of roots colonized by AM fungi. Compared to control treatment, arbuscule formation decreased by 55 and 14% under water excess and water deficit, respectively. Vesicle formation increased 256% in water excess treatment and did not change under water deficit treatment. L. tenuis plants subjected to water deficit or excess treatments could grow, nodulated and maintained a symbiotic association with AM fungi by different strategies. Under water excess, L. tenuis plants decreased root growth and increased shoot growth to facilitate water elimination by transpiration. Under water deficit, L. tenuis plants decreased root growth but also shoot growth which in turn significant decreased the shoot/root ratio. In the present study, under water excess conditions AM fungi reduced nutrient transfer structures (arbuscules), the number of entry points and spore, and hyphal densities in soil, but increased resistance structures (vesicles). At water deficit, however, AM fungi reduced external hyphae and arbuscules to some extent, investing more in maintaining a similar proportion of vesicles in roots and spores in soil compared to control treatment. [ABSTRACT FROM AUTHOR]

Lotus tenuis (Wadst. & Kit.) is a perennial legume widely grown for pasture in the flood-prone and salt affected Pampa region of Argentina. The physiology of salt and waterlogging tolerance in L. tenuis (four cultivars) was evaluated, and compared with Lotus corniculatus (three cultivars); the most widely cultivated Lotus species. Overall, L. tenuis cultivars accumulated less Na+ and Cl−, and more K+ in shoots than L. corniculatus cultivars, when exposed to 200 mM NaCl for 28 days in aerated or in stagnant solutions. Root porosity was higher in L. tenuis cultivars due to greater aerenchyma formation. In a NaCl dose–response experiment (0–400 mM NaCl in aerated solution), L. tenuis (cv. Chaja) accumulated half as much Cl− in its shoots than L. corniculatus (cv. San Gabriel) at all external NaCl concentrations, and about 30% less shoot Na+ in treatments above 250 mM NaCl. Ion distributions in shoots were determined for plants at 200 mM NaCl. L. tenuis (cv. Chaja) again accumulated about half as much Cl− in old leaves, young leaves and stems, compared with concentrations in L. corniculatus (cv. San Gabriel). There were not, however, significant differences between the two species for Na+ concentrations in the various shoot tissues. The higher root porosity, and maintenance of lower shoot Cl− and Na+ concentrations in L. tenuis, compared with L. corniculatus, contributes to the greater tolerance to combined salt and waterlogging stress in L. tenuis. Moreover, significant variation for tolerance to combined salinity and waterlogging stress was identified within both L. tenuis and L. corniculatus. [ABSTRACT FROM AUTHOR]

Explores the impact of seed-to-seed allelopathy between two invaders of burned Pampa grasslands in Argentina. Use of the Lotus tenuis seeds as a source of allelopathic compounds; Subjection of L. tenuis to biological assay to determine growth inhibition capacity; Application of methods for leachate sterilization to note Carduus acanthoides response.

To analyse the putative effects of putrescine on the plant response to salinity, micropropagated Lotus tenuis plants from wild-type and transgenic lines harbouring the pRD29A::oat arginine decarboxylase (ADC, EC 4.1.1.19) construct were subjected to a gradual increase in salinity that was applied gradually by means of sodium chloride irrigation (from 0 to 0.3 mol L−1) every 5 days up to the maximum concentration. At the end of the experiment, the transgenic lines were healthier than the wild-type plants and displayed a smaller reduction in shoot biomass and a slight increase in root growth in response to stress. The overexpression of ADC increased osmotic adjustment (5.8-fold) via the release of proline. The salinity treatment doubled the potassium uptake by roots from transgenic ADC stressed plants with a concomitant decrease in the accumulation of sodium, balancing the Na+/K+ ratio. Analysis of gene expression, enzymatic activities and hormone metabolism suggests a crosstalk between polyamines and abscisic acid in response to salinity via modulation of the abscisic acid biosynthesis-related enzyme 9-cis-epoxycarotenoid dioxygenase (EC 1.13.11.51) at the transcriptional level. [ABSTRACT FROM AUTHOR]

Five Lotus tenuis genotypes showing 2n pollen production greater than 5% and producing 4x progenies in 4x(male sterile Lotus corniculatus) x 2x crosses were found in different natural populations. Meiotic analyses of these plants showed some second metaphases with disoriented spindles, i e parallel and tripolar spindles which resulted in diads and triads, respectively. Because useful genes for winter growth and resistance to powdery mildew from L. tenuis can be introgressed into L corniculatus via 2n gametes, a program of selection was started to increase the occurrence of 2n gamete production in L. tenuis. Controlled crosses were performed between genotypes producing 2n gametes and the progenies were checked for 2n pollen production and meiotic aberration, following the same methodologies as used for the parental plants. Although in some progeny plants the frequency of 2n gamete production increased remarkably, the overall progeny level of 2n gamete production remained unchanged. This suggested that different genes for meiotic aberration exist in natural populations and/or differential seed-setting ability exists between genotypes. Diallel crosses between selected genotypes confirmed this hypothesis. Evaluation of 2n pollen production of clones grown under different temperature regimes (warm vs temperate) showed that, in L. tenuis, the effects of genotype, temperature and genotype x temperature interaction are significant In particular, high temperature increases the level of 2n gamete production in L. tenuis. [ABSTRACT FROM AUTHOR]

The tropic response of Lotus tenuis shoots under conditions of full sunlight (FS) or artificial shade (AS) has been studied in relation to their endogenous levels of gibberellins (Gas) and sucrose. Single-node explants with one axillary branch each were incubated in darkness with different concentrations of sucrose, GA3, B9 or their combinations, or whole plants were treated with FS, AS, AS + uniconazole, or AS + cimectacarb. High sucrose concentration supplied via xylem turned the axillary branch growth diagravitropic. GA3 reversed the effect of sucrose, both in shoot sections and whole plants, turning the axillary branch growth ortotropic and diminishing the sucrose levels at the shoot bases. High irradiance induced a prostrate growth of the shoots. Artificial shade increased both internode and branch length and induced an upward curvature of the shoots. This was correlated with a lower sucrose concentration and increased content of GA 1and GA3 Cimectacarb and uniconazole reversed the AS effects, although the sucrose content in the shoots remained low. These results are direct evidence that gravitropism of L. tenuis shoots under different light intensities, but of similar light quality, is controlled by the levels of GA1 and GA3 and sucrose. [ABSTRACT FROM AUTHOR]

Determines the mechanisms of 2n pollen formation in Lotus tenuis or Fabaceae. Description of n and 2n pollen morphology with light and scanning electron microscopy; Shapes and sizes of pollen.

Nitrogen fixation activity was determined for Lotus tenuis, Medicago lupulina and Trifolium pratense. The three species grew in clones in grassland in an area reclaimed from brackish water in the 1940s. The N2[C2H2]-fixation was measured in soil cores throughout 1974 and 1975. From cores taken in dense and uniform stands of the species, the yearly N2[C2H2]-fixation at maximum cover was estimated. L. tenuis fixed about 4 g N m-2 yr-1 (area with max. cover 130%). i.e. 30-56% of its requirement. Both M. lupulina and T. pratense fixed about 7 g N m-2 yr -1 (maximum cover 37% and 80%) i.e. 67% of their N-requirement. Average N2[C2H2]-fixation for the whole area was 0.4 g N m-2 yr-1, considerably less than the N-addition through rainfall. [ABSTRACT FROM AUTHOR]

The article offers information on the two plant species found in Kenton County, Kentucky on June 5, 2007. The Lotus tenuis or narrow-leaved birdsfoot's-trefoil is described to have a shorter calyx tube, smaller corolla and narrower leaflets of the medial leaves than its closely related congener, Lotus corniculatus. The Puccinellia distans or weeping alkali grass is primarily found in coastal saline areas such as those created by winter rock salting along roadsides.

Two meiotic mutants of L. tenuis (2n = 2x = 12) producing unreduced pollen are described When crossed to male sterile L eornlculatu3 (2n = 4x = 24) plants, all progeny plants were morphologically similar to L. corniculatus had 2n = 24 chromosomes, and in the cross, were fully compatible with L. corniculatus, indicating that the male parent plants were 2n-pollen producers. One of them also had 'giant' pollen grains In metaphase 11 of both genotypes. there were parallel and tripolar spindles leading to dyad and triad formation, the latter being found most frequently. Since both the above-mentioned mechanisms result in first-division restitution-type microspores. the genotypes examined could be useful in breeding Lotus. [ABSTRACT FROM AUTHOR]

Background and aims: The aim of this work was to evaluate the ability of P fertilization and phosphate-solubilizing bacteria (PSB) inoculation to promote the growth of L. tenuis in typical soils of the Salado River Basin (Argentina) with low P availability. Methods: Aboveground biomass and P and N levels were evaluated in field-grown L. tenuis plants inoculated with Pantoea eucalypti M91, either without fertilization or in combination with phosphate rock and triple superphosphate (TSP). The impact of P fertilization and inoculation on the symbiotic interactions between L. tenuis and native rhizobia bacteria and arbuscular mycorrhizal fungi was also evaluated. Results: Inoculation with M91 increased the L. tenuis biomass production and P concentration in shoots, at an early stage of plant growth. The combined treatment of inoculation with M91 and TSP significantly increased the P and N content in shoots compared to non-inoculated plants, fertilized or not. P. eucalypti M91 was found to endophytically colonize roots and leaves of L. tenuis plants grown in vitro and also under field conditions. Conclusions: The results suggesting that inoculation of L. tenuis with the PSB such as P. eucalypti M91 strain might allow more efficient use of N and P and a more sustainable option for grasslands producers from the Salado River Basin, in order to reduce costs and avoid increased levels of P insoluble in soils. [ABSTRACT FROM AUTHOR]

Saline, alkaline and mixed saline-alkaline conditions frequently co-occur in soil. In this work, we compared these plant stress sources on the legume Lotus tenuis, regarding their effects on shoot growth and leaf and stem anatomy. In addition, we aimed to gain insight on the plant physiological status of stressed plants. We performed pot experiments with four treatments: control without salt (p H = 5.8; EC = 1.2 dS·m−1) and three stress conditions, saline (100 m m Na Cl, p H = 5.8; EC = 11.0 dS·m−1), alkaline (10 m m Na HCO3, p H = 8.0, EC = 1.9 dS·m−1) and mixed salt-alkaline (10 m m Na HCO3 + 100 m m Na Cl, p H = 8.0, EC = 11.0 dS·m−1). Neutral and alkaline salts produced a similar level of growth inhibition on L. tenuis shoots, whereas their mixture exacerbated their detrimental effects. Our results showed that none of the analysed morpho-anatomical parameters categorically differentiated one stress from the other. However, Na Cl- and Na HCO3-derived stress could be discriminated to different extents and/or directions of changes in some of the anatomical traits. For example, alkalinity led to increased stomatal opening, unlike Na Cl-treated plants, where a reduction in stomatal aperture was observed. Similarly, plants from the mixed saline-alkaline treatment characteristically lacked palisade mesophyll in their leaves. The stem cross-section and vessel areas, as well as the number of vascular bundles in the sectioned stem were reduced in all treatments. A rise in the number of vessel elements in the xylem was recorded in Na Cl-treated plants, but not in those treated exclusively with Na HCO3. [ABSTRACT FROM AUTHOR]

The impact of different defoliation intensities on the ability of Lotus tenuis plants to regrowth, mobilise nutrients and to associate with native AM fungi and Rhizobium in a saline-sodic soil was investigated. After 70 days, plants were subjected to 0, 25, 50, 75 and 100% defoliation and shoot regrowth was assessed at the end of subsequent 35 days. Compared to non-defoliated plants, low or moderate defoliation up to 75% did not affect shoot regrowth. However, 100% treatment affected shoot regrowth and the clipped plants were not able to compensate the growth attained by non-defoliated plants. Root growth was more affected by defoliation than shoot growth. P and N concentrations in shoots and roots increased with increasing defoliation while Na+ concentration in shoots of non-defoliated and moderately defoliated plants was similar. Non-defoliated and moderately defoliated plants prevented increases of Na+ concentration in shoots through both reducing Na+ uptake and Na+ transport to shoots by accumulating Na+ in roots. At high defoliation, the salinity tolerance mechanism is altered and Na+ concentration in shoots was higher than in roots. Reduction in the photosynthetic capacity induced by defoliation neither changed the root length colonised by AM fungi nor arbuscular colonisation but decreased the vesicular colonisation. Spore density did not change, but hyphal density and Rhizobium nodules increased with defoliation. The strategy of the AM symbiont consists in investing most of the C resources to preferentially retain arbuscular colonisation as well as inoculum density in the soil. [ABSTRACT FROM AUTHOR]

Both saline and alkaline conditions frequently coexist in nature; however, little is known about the effects of alkaline and salt-alkaline stresses on plants. We performed pot experiments with four treatments, control without salt addition and three stress conditions-neutral, alkaline, and mixed salt-alkaline-to determine their effects on growth, nutrient accumulation and root architecture in the glycophytic species Lotus tenuis. Neutral and alkaline salts produced a similar detrimental effect on L. tenuis growth, whereas the effect of their combination was synergistic. Neutral salt addition, alone or mixed with NaHCO, led to significant leaf Na build up and reduced K concentration. In contrast, in plants treated with NaHCO only, Na levels and the Na/K ratio remained relatively unchanged. Proline accumulation was not affected by the high pH in the absence of NaCl, but it was raised by the neutral salt and mixed treatments. The total root length was reduced by the addition of NaCl alone, whereas it was not affected by alkalinity, regardless of the presence of NaCl. The topological trend showed that alkalinity alone or mixed with NaCl turned the root more herringbone compared with control roots, whereas no significant change in this index was observed in the treatment with the neutral salt only. The pattern of morphological changes in L. tenuis root architecture after the alkaline treatment (in the absence of NaCl) was similar to that found in the mixed salt-alkaline treatment and different from that observed in neutral salt. A unique root morphological response to the mixed salt-alkaline stress was the reduction in the ratio between xylem vessels and root cross-sectional areas. [ABSTRACT FROM AUTHOR]

Abstract: Lotus tenuis Wald et Kit and Lotus corniculatus L. are conspicuous elements of the agricultural landscape for cattle production. In South America, commercial L. tenuis stocks usually present contaminations with L. corniculatus, what brings about an important economical injure to the forage producers. A way to reduce or avoid loses is to assess the purity degree of L. tenuis seed lots before seeding. Methods so far described for the diagnosis of Lotus species when flowers are not available are lengthy, time consuming, need the implementation of sophisticated laboratories and are relatively expensive. It has been shown that Lotus species accumulate variable proanthocyanidins amounts, which can be easily visualized by a simple and rapid staining method. In this work, we demonstrate that the leaf PA content is a specific trait of L. tenuis and L. corniculatus and hence, it allows the unambiguous differentiation between both species, even at an early phenological stage. [Copyright &y& Elsevier]

The article presents the results of a study on the effect of level of fertilization on the competition between Lotus tenuis and Cynodon dactylon both in above and underground soil. The results show that greater fertilizer use efficiency was shown by Cynodon dactylon than Lotus tenuis. The ability of Cynodon dactylon to interact with soil and compete for nutrients and water is more efficient than Lotus tenuis because of its low root hydraulic resistance and high specific root length.

A perennial forage legume species tolerant to water stress would be useful to improve pasture and animal productivity in the central zone of Chile. The growth, dry-matter (DM) production, and drought tolerance of twelve accessions of Lotus tenuis Waldst & Kit, Syn. L. glaber, naturalized in Chile were evaluated with the objective to select contrasting genotypes, tolerant and sensitive to drought, for future breeding programmes. The accessions were sown in pots of 1.3 L containing a volcanic soil (Andisol). A completely randomized design with all combinations of Lotus accessions and four water treatments [100, 70, 40, and 10% of soil water availability (SWA)] was used. The relative rate of stem elongation (RRSE), the shoots and roots DM production, the relative water content (RWC), and the specific leaf area (SLA) were measured. A drought-sensitivity index (DSI) and the interaction genotype×environment were calculated. The RRSE, the DM production, RWC, and SLA all showed a significant reduction (P<0.05) in the treatment with the higher water restriction (10% SWA). There were significant differences (P<0.05) within RRSE and DM production genotype means, but the RWC and SLA did not differ among populations. The DSI varied broadly among genotypes, from 0.49 to 1.34, and was correlated negatively with DM production under water stress (10% SWA). It was concluded that the Lotus tenuis populations showed water-stress tolerance genetic variability, with accessions Lt14 and Lt4 the most contrasting. These findings will permit us to identify chromosomal regions associated with drought-tolerant genotypes which will allow us to accelerate the development of cultivars adapted to water-restricted environments. [ABSTRACT FROM AUTHOR]

Development of the unisexual maize inflorescences requires the abortion of pistillate primordia in the florets of the developing tassel and the arrest of staminate primordia in the florets of the developing ears. Mutations of many genes that lie within this sexual differentiation pathway, such as tasselseed1 ( ts1), or that influence this pathway, such as mediator of paramutation 1 ( mop1), result in feminization of the normally male tassel. Here, we show the loss of mop1 or ts1 function results in increased mRNA levels for several members of the SBP-box gene family. Our analyses of this family expand the number of maize SBP-box genes from 9 to 31 members. Intron–exon structures as well as phylogenetic data support the division of these family members into six groups. The SBP-box genes upregulated in feminized tassels fall into two groups, share common structural motifs and include the presence of a target site for miR156. Small RNA blots show miR156 levels are decreased in both mop1 and ts1 mutants. While there is a correlation between miR156 levels and SBP-box gene transcript levels, this correlation is not absolute, and thus we hypothesize that decreased levels of miR156 may provide competency for SBP-box gene upregulation by other common factors yet to be identified. We present a model that provides a putative link between ts1, ts2, ts4, Ts6, and mop1 in the sex-determination pathway. [ABSTRACT FROM AUTHOR]

The tropic response of Lotus tenuis shoots under conditions of full sunlight (FS) or artificial shade (AS) has been studied in relation to their endogenous levels of gibberellins (Gas) and sucrose. Single-node explants with one axillary branch each were incubated in darkness with different concentrations of sucrose, GA3, B9 or their combinations, or whole plants were treated with FS, AS, AS + uniconazole, or AS + cimectacarb. High sucrose concentration supplied via xylem turned the axillary branch growth diagravitropic. GA3 reversed the effect of sucrose, both in shoot sections and whole plants, turning the axillary branch growth ortotropic and diminishing the sucrose levels at the shoot bases. High irradiance induced a prostrate growth of the shoots. Artificial shade increased both internode and branch length and induced an upward curvature of the shoots. This was correlated with a lower sucrose concentration and increased content of GA 1and GA3 Cimectacarb and uniconazole reversed the AS effects, although the sucrose content in the shoots remained low. These results are direct evidence that gravitropism of L. tenuis shoots under different light intensities, but of similar light quality, is controlled by the levels of GA1 and GA3 and sucrose. [ABSTRACT FROM AUTHOR]

The narrow-leaf trefoil is a widely used forage plant in temperate and subtemperate areas. It is the object of extensive improvement programs and research, which has generated a large body of literature. A few decades ago it was discovered that its traditional scientific name, Lotus tenuis Waldst. & Kit. ex Willd., had to be superseded by an older name, L. glaber Mill. It was then proposed to permanently reject the name L. glaber, thus allowing L. tenuis to continue in use for the narrow-leaf trefoil. The rejection proposal for the name L. glaber was finally accepted by the 17th International Botanical Congress (IBC) in July 2005, so L. tenuis is now the scientific name for the narrow-leaf trefoil. [ABSTRACT FROM AUTHOR]

Provides information on saline tolerant narrow-leaf trefoil germplasm. Phytoremediation and crop rotation value in saline soil reclamation; Process on how the germplasm was developed; Key features and advantages.

Deals with the two lines of narrowleaf and big trefoil plants from the Agricultural Research Service that can help breeders develop improved forages for livestock and wildlife. Popularity of birdsfoot trefoil; Information the National Plant Germplasm System.

The Flooding Pampas is the most important livestock region of Argentina, but is a region where replacement of originally natural, perennial tussock grasses by pasture species is changing the heterogeneity of the grassland system. We evaluated the response of grassland bird assemblages of the Flooding Pampas to planting of Lotus tenuis (Lotus) pasture, which mainly modifies vegetation structure by reducing vertical heterogeneity. Species richness and abundance of birds were compared between fields of Lotus pasture and semi-natural grasslands. Avian species richness and abundance were both greater in semi-natural grassland than in Lotus pasture. When grouped by nesting habits (grassland specialists, generalists), species richness and abundance of grassland specialists was greater in semi-natural grassland, whereas richness and abundance of generalist species was greater in Lotus pasture. An indicator-species analysis showed that five grassland birds were closely linked to semi-natural grassland vegetation, with two of those species - Hudson's Canastero (Asthenes hudsoni) and Bay-capped Wren-Spinetail (Spartonoica maluroides) - of conservation concern.1 In contrast, generalist species, such as Southern Lapwings (Vanellus chilensis) and Burrowing Owls (Athene cunicularia), were associated with Lotus pasture. Planting of Lotus pasture has negative effects on species that naturally occur in tussock grassland. Grassland management methods, such as intercropping and rotational grazing, could help reconcile the effects of livestock production and the conservation grassland bird conservation in the Flooding Pampas. [ABSTRACT FROM AUTHOR]

Background and Aims Flooding and grazing are major disturbances that simultaneously affect plant performance in many humid grassland ecosystems. The effects of flooding on plant recovery from defoliation were studied in two species: the grass Paspalum dilatatum, regrowing primarily from current assimilation; and the legume, Lotus tenuis, which can use crown reserves during regrowth. Methods Plants of both species were subjected to intense defoliation in combination with 15 d of flooding at 6 cm water depth. Plant recovery was evaluated during a subsequent 30-d growth period under well-watered conditions. Plant responses in tissue porosity, height, tiller or shoot number and biomass of the different organs were assessed. Key Results Flooding increased porosity in both P. dilatatum and L. tenuis, as expected in flood-tolerant species. In P. dilatatum, defoliation of flooded plants induced a reduction in plant height, thus encouraging the prostrated-growth response typical of defoliated plants rather than the restoration of contact with atmospheric oxygen, and most tillers remained submerged until the end of the flooding period. In contrast, in L. tenuis, plant height was not reduced when defoliated and flooded, a high proportion of shoots being presented emerging above water (72 %). In consequence, flooding plus defoliation did not depress plant recovery from defoliation in the legume species, which showed high sprouting and use of crown biomass during regrowth, whereas in the grass species it negatively affected plant recovery, achieving 32 % lower biomass than plants subjected to flooding or defoliation as single treatments. Conclusions The interactive effect of flooding and defoliation determines a reduction in the regrowth of P. dilatatum that was not detected in L. tenuis. In the legume, the use of crown reserves seems to be a key factor in plant recovery from defoliation under flooding conditions. [ABSTRACT FROM AUTHOR]

In Argentina narrowleaf trefoil (Lotus glaber) predominates over broadleaf trefoil (Lotus corniculatus). Researchers have suggested this predominance occurs because L. glaber grows better at low levels of P availability. I studied the effect of increasing phosphorus (P) nutrition and mycorrhizal growth response of Lotus corniculatus and Lotus glaber in a soil of low available P. L. corniculatus was more efficient in P utilization than L. glaber and produced larger yields of shoot tissue per unit of P. The critical P concentration, measured as a percentage of P in the shoot required to achieve 90% of maximum shoot yield, was 0.22 in L. corniculatus and 0.28 in L. glaber. The roots of both two species were heavily infected by arbuscular micorrhizae (AM), and both mycorrhizal and nonmycorrhizal plants responded strongly to added P in soil. This suggests that both species are at no advantage or disadvantage whether mycorrhizal or nonmicorrhizal. The fraction of roots colonized by AM fungi differed between species at low levels of added P but was similar at high levels of added P. The specific root length (cm g-1) of mycorrhizal plants was greatest in L. corniculatus when P was insufficient to achieve maximum growth. The lower critical P concentration and the higher specific root length at low levels of P nutrition may be why L. corniculatus is superior to L. glaber in soils low in P. Therefore, the predominance of L. glaber compared with L. corniculatus in Argentinean soils is not due to ability of L. glaber to grow better in soil at low levels of P availability. [ABSTRACT FROM AUTHOR]

This review presents a new model for a multidisciplinary approach to development of modern forage cultivars to enable high-value meat and wool production in the mixed farming zones of Australia. Many pasture improvement activities focus on biomass production, filling novel agro-ecological niches, fixing nitrogen and phenotypic markers. Key traits that drive profitability of livestock, such as feeding value (FV), and nutritive value (NV), are rarely considered in a timely manner. Farmers are often not seriously engaged until late in the development pipeline. Of the nearly 10 000 publications that reference forage improvement or breeding and Australia, less than 5% also reference ruminant production factors such as FV, metabolisable energy, digestibility, methane or toxicity in the abstract, title or keywords. We make the case that the late engagement of livestock science and farmers results in early discarding of potentially valuable genetic material. This in turn may contribute to market and nutritional limitations that contribute to the high failure rate of new pasture cultivars. Four case studies demonstrated the within and among species variation in FV and NV. The first showed the variability in dry matter digestibility and crude protein of 20 species of herbaceous perennials at different stages of maturity. A second study with annual legumes, grasses and brassicas indicated highly significant differences in the rate of decline of NV over time and across species. The third case study focused on commercial and experimental accessions of lucerne and demonstrated highly significant differences among accessions in NV, with a doubling of livestock growth expected with the lowest and highest NV accessions. These case studies demonstrated the potential risks associated with evaluation of FV and NV after most of the germplasm has been excluded. The final case study described a different model that was used in the identification and commercialisation of a woody perennial species. This process incorporated a multidisciplinary team, farmers and livestock-relevant characteristics from the start. In 9 years, Anameka™ oldman saltbush was selected for higher palatability, 20% higher organic-matter digestibility and eight times more biomass than the average of the original genetic material. [ABSTRACT FROM AUTHOR]

In Australia, 71% of agricultural greenhouse gas (GHG) emissions are enteric methane (CH4), mostly produced by grazing sheep and cattle. Temperate low CH4 yielding legumes and herbs can mitigate enteric CH4 production, but system-level GHG emissions need to be considered. The aims of the study were to: (1) devise a framework to assess GHG reductions when introducing low CH4 yielding species; (2) assess mechanisms of CH4 reduction in temperate legume and herb species for Australia; (3) use a case study to demonstrate expected changes to system-level GHG emissions with the introduction of low CH4 yielding legumes; and (4) identify knowledge gaps and research priorities. Results demonstrate lowering emissions intensity (kg CO2-equivalent/kg product) is crucial to mitigate GHG emissions, but livestock productivity is also important. Several pasture species have anti-methanogenic properties, but responses often vary considerably. Of the species investigated biserrula (Biserrula pelecinus) has great potential to reduce enteric CH4 emissions, but in a case study its emission intensity was similar to subterranean clover (Trifolium subterraneum) but higher than lucerne (Medicago sativa). We conclude that there are temperate legumes and herbs with anti-methanogenic properties, and/or high productivity that could reduce total CH4 emissions and emissions intensity of ruminant livestock production. There is also great diversity in some plant genotypes that can be exploited, and this will be aided by more detailed understanding of plant secondary compounds associated with CH4 reduction. This review suggests an opportunity to formulate pasture species mixtures to achieve reduced CH4 emissions with greater or equal livestock production. Temperate low methane (CH4) yielding legumes and herbs can reduce enteric methane, but greenhouse gas emissions at a system level need to be considered. This review identified several pasture species with anti-methanogenic properties, with biserrula having the most potential to reduce enteric CH4. However, a case study demonstrated that emission intensity of biserrula was similar to that of subterranean clover but higher than that of lucerne. An opportunity exists to formulate pasture mixtures to reduce CH4 and increase livestock production. [ABSTRACT FROM AUTHOR]

The broad-spectrum herbicide glyphosate (N – phosphonomethylglicine) is the most common pesticide used in the Humid Pampa, the main agricultural region in Argentina. According to agronomical practices and topogeographical characteristics of the region, rhizoremediation arises as a promising technology to mitigate glyphosate impact on health and agroecosystems. Lotus corniculatus L. (birdsfoot trefoil) and Lotus tenuis Waldst. et Kit. (= Lotus glaber Mill., narrowleaf trefoil) were selected to carry out tolerance studies as the starting point of a rhizoremediation process. L. corniculatus presented the highest root and foliar tolerance to glyphosate, corresponding to 5.0 mg kg −1 and 700 g ha −1 respectively. The enzyme enolpyruvylshikimate-3-phosphate synthase ( EPSP synthase ) partial cDNA sequence and whole plant shikimate accumulation assay were performed on L. corniculatus in order investigate tolerance mechanisms. No amino acid substitution related to glyphosate tolerance was found on EPSP synthase cDNA sequence. The shikimate accumulation study indicates that limited uptake and/or translocation of the herbicide is the most probable tolerance mechanism. Results obtained in this study, plus the productive and adaptive advantages of L. corniculatus make it a valuable candidate to develop rhizoremediation strategies. [ABSTRACT FROM AUTHOR]

Implementation of the saline drainage water reuse system proposed for the westside of the San Joaquin Valley (SJV) of California requires development of sustainable cropping systems, which incorporate useful, salt-tolerant agronomic species. Ion composition in the saline drainage effluents present in the SJV is unique, with Na+, SO42-, Cl-, Mg2+ and Ca2+ predominating in that order. To identify potentially suitable crops for reuse systems, 10 forages were tested in greenhouse sand cultures located at USDA-ARS George E. Brown Jr. Salinity Laboratory, Riverside, California. Crops were: alfalfa (Medicago sativa L.) cvs. ‘Salado’ and ‘SW 9720’; narrowleaf trefoil (Lotus glaber Greene) cv. ‘PI 608022’; broadleaf trefoil (L. ulginosus Schk.) cv. ‘Big’; tall wheatgrass (Agropyron elongatum (Host) Beauv.) cv. ‘Jose’; alkali sacaton (Sporobolus airoides Torr.); kikuyugrass (Pennisetum clandestinum Hochst. Ex Chiov.) cv. ‘Whittet’; paspalum (Paspalum vaginatum Swartz) cvs. PI ‘299042’ and ‘Polo’; and bermudagrass (Cynodon dactylon L. Pers.) cv. ‘Tifton’. Two saline treatments, 15 and 25dSm-1, were imposed. Shoots were sub-sampled for mineral ion analysis when the forages were harvested. Patterns of shoot ion concentrations were unique for each species and varied with salinity level, external ion ratios, harvest date and plant age. Plant preference for K+ over Na+ did not appear to be a reliable predictor of salt tolerance. Salt-tolerant crops, such as kikuyugrass and bermudagrass, were highly selective for K+ (SK,Na ∼ 200 to 400), whereas selectivity coefficients for the equally salt-tolerant grasses, alkali sacaton and tall wheatgrass, ranged from 20 to 40. The forages were highly selective for K+ over Mg2+ despite unusually low K+:Mg2+ ratios in the external solutions. Total-S in the herbage was high and generally increased as external SO42- increased. Based on sustained nutritional health and lack of visual signs of toxicity or deficiency symptoms, several of the forages tested show promise as suitable candidates for the saline–sodic water reuse systems. [Copyright &y& Elsevier]

In the rain‐fed mixed‐farming systems of southern Australia, the consistent supply of high‐value forage is limited by a range of climatic, edaphic and systems constraints. Over 2 years, we compared biomass production and nutritional value of 30 accessions of perennial legumes, and predicted intake, grazing days and growth of ewes and lambs. There was significant variation in nutritional value and biomass production between and within species. Lucerne (Medicago sativa) and sulla (Hedysarum coronarium) produced the greatest amount of biomass and energy. There was variability among accessions in digestibility (DMD), acid detergent fibre (ADF) and crude protein, and the rate of change in these traits as plants matured. Trifolium species had the highest DMD across all growth stages. Hairy canary clover (Dorycnium hirsutum), erect canary clover (Dorycnium rectum), greater birdsfoot trefoil (Lotus uliginosus), Australian trefoil (Lotus australis) and running postman (Kennedia prostrata) had energy levels that would not maintain liveweight of mature sheep. In the second year, species differed in response to harvesting treatments. Lucerne and sainfoin (Onobrychis viciifolia) were more productive under a frequent cutting regime. Accessions of white clover (Trifolium repens), red clover (Trifolium pratense), alsike clover (Trifolium hybridum), cullen (Cullen australasicum), strawberry clover (Trifolium fragiferum), sainfoin and birdsfoot trefoil (Lotus corniculatus) showed some promise, while Tedera (Bituminaria bituminosa) and milkvetch (Astragalus cicer) performed poorly under the experimental conditions. We conclude by discussing additional agronomic and nutritional factors that need consideration when developing novel perennial legumes for mixed‐farming systems in the context of a changing climate. [ABSTRACT FROM AUTHOR]

This review examines the prospect of improving perennial legume adaptation to grazed mixed pasture swards across the higher-altitude regions of south-eastern Australia through improved management, particularly as it relates to soil fertility. The range of adapted perennial species available to farmers often remains limited to only one perennial forage legume species, white clover (Trifolium repens L.). Despite recent advances in cultivars for increased persistence in dryland environments, white clover remains sensitive to drought with its inherently shallow root system and limited capacity to restrict water loss from herbage. With few alternative species likely to become widely available in the foreseeable future, prospects for extending the boundaries of perennial legume adaptation likely rely on a dual approach of improving soil fertility and further genetic improvement in white clover. Improved soil fertility would focus on overcoming soil acidity and addressing nutrient deficiencies, particularly of phosphorus, potassium, boron and molybdenum, which tend to be more widespread in the target region. Addressing these soil constraints would alleviate periodic moisture stress by: (1) increased water availability through improved infiltration and soil hydraulic properties; (2) increased root growth to maximise exploration of the soil volume; and (3) better maintenance of plant cell structures to foster improved osmotic regulation. However, the extent to which white clover adaption may be extended remains an issue of further research. This review highlights an opportunity for further genetic improvement of white clover by focusing on improving the capacity to recover from periodic droughts through seedling regeneration. Further breeding efforts in white clover should examine the feasibility of selecting for hard seed characteristics more similar to the best-adapted subterranean clover (Trifolium subterraneum L.) cultivars across this region to promote ongoing seedling regeneration. Poor legume persistence under variable climatic conditions compromises the productivity of permanent pasture swards in the Tablelands environments of south-eastern Australia. With few viable alternatives presently available, the drought-sensitive species, white clover, remains the best adapted perennial legume across much of the target region. This review examines the prospects for more strategic use of fertilisers and soil ameliorants, in combination with additional plant breeding for seedling regeneration, to improve the survival and recovery of white clover following periodic drought. [ABSTRACT FROM AUTHOR]

Condensed tannins (CTs) account for up to 20% of the dry matter in forage legumes used as ruminant feeds. Beneficial animal responses to CTs have included improved growth, milk and wool production, fertility, and reduced methane emissions and ammonia volatilization from dung or urine. Most important is the ability of such forages to combat the effects of gastrointestinal parasitic nematodes. Inconsistent animal responses to CTs were initially attributed to concentration in the diet, but recent research has highlighted the importance of their molecular structures, as well as concentration, and also the composition of the diet containing the CTs. The importance of CT structural traits cannot be underestimated. Interdisciplinary research is the key to unraveling the relationships between CT traits and bioactivities and will enable future on‐farm exploitation of these natural plant compounds. Research is also needed to provide plant breeders with guidelines and screening tools to optimize CT traits, in both the forage and the whole diet. In addition, improvements are needed in the competitiveness and agronomic traits of CT‐containing legumes and our understanding of options for their inclusion in ruminant diets. Farmers need varieties that are competitive in mixed swards and have predictable bioactivities. This review covers recent results from multidisciplinary research on sainfoin (Onobrychis Mill. spp.) and provides an overview of current developments with several other tanniniferous forages. Tannin chemistry is now being linked with agronomy, plant breeding, animal nutrition, and parasitology. The past decade has yielded considerable progress but also generated more questions—an enviable consequence of new knowledge! [ABSTRACT FROM AUTHOR]

Cattle production based on natural pastures is often subject to flooding periods, which affect plant performance and as a result, forage production. Although most forage legumes are not tolerant to flooding, Lotus spp. are outstanding alternatives, since species, such as L. tenuis (Lt) and L. corniculatus (LcT), have high forage quality and are adaptable to different environments. We recently obtained a L. tenuis × L. corniculatus hybrid (LtxLc) with potential new cultivar traits, although its tolerance to flooding stress has not yet been evaluated. In the present study, the performance of LtxLc, its parental diploid accessions, the model legume L. japonicus and tetraploid LcT were evaluated under 55 days of partial submergence stress and a 35‐day recovery period. Physiological, morphological and anatomical traits were analysed, showing that tolerance to partial submergence was positively associated with aerenchyma and adventitious root formation and relative growth rates. Overall, Lt and LtxLc showed the best responses under stress and during the recovery period. Nevertheless, the higher forage value of LtxLc makes it recommendable for use in environments affected by flooding. Our results could be used as breeding criteria for the generation of new cultivars tolerant to partial submergence stress. [ABSTRACT FROM AUTHOR]

The presence of native grasses in communities can suppress native forbs through competition and indirectly benefit these forbs by suppressing the invasion of highly competitive exotic species. We conducted a greenhouse experiment to examine the potential of direct and indirect interactions to influence the aboveground biomass of four native forb species in the presence of the native perennial grass Schizachyrium scoparium and exotic invasive Lespedeza cuneata. We examined patterns of growth for the invasive legume, the perennial grass, and four native species in four scenarios: 1) native species grown with the grass, 2) native species grown with the legume, 3) native species grown with both the grass and legume together, and 4) native species grown alone. Schizachyrium scoparium significantly decreased biomass of all forb species (p<0.05). In contrast, L. cuneata alone only significantly affected biomass of Asclepias tuberosa; L. cuneata increased the biomass of A. tuberosa only when the grass was present. When S. scoparium and L. cuneata were grown together, L. cuneata had significantly lower biomass (p = 0.007) and S. scoparium had significantly greater biomass (p = 0.002) than when each grew alone. These reciprocal effects suggest a potential pathway by which L. cuneata could alter forb diversity in grassland communities In this scenario, L. cuneata facilitates grass growth and competition with other natives. Our results emphasize the importance of monitoring interactions between exotic invasive plant species and dominant native species in grassland communities to understand pathways of plant community change. [ABSTRACT FROM AUTHOR]

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The aim of this research was to provide tools for the profitable and environmentally friendly P fertilization of potato (Solanum tuberosum L.) crops. The objectives were: (i) to examine the relationships between the available soil phosphorus index (Pav), as determined by Bray1, Mehlich 3, Olsen, and CaCl2 in Mollisols, and potato yields and (ii) to identify the P fertilization rates required to obtain the maximum agronomic yields, considering the environmental risk of P loss. The study was conducted from 2005 to 2014 in soils with a wide range of initial available P levels (8.6-50.0 mg kg-1 Bray1; from a depth of 0 to 20 cm in which irrigated potato crops fertilized with P were cultivated. The linear-plateau, quadratic-plateau, and Cate-Nelson models were used to analyze crop responses to P and to determine the phosphorus threshold (Pt) required to identify soils with positive responses to P fertilization. The Pt was 32 mg kg-1 for Bray1 and Mehlich 3, 11 mg kg-1 for Olsen and 2.8 mg kg-1 for CaCl2. Recommended P rates were defined based on the initial soil Pav index, the quantity of P removed by the crop for a specific yield, the P required to increase the initial soil P to the Pt, and the environmental Pt. Soil Bray1 determined postharvest confirmed that the P fertilizer recommendation was appropriate in Mollisols soils. [ABSTRACT FROM AUTHOR]

Alien plants pose a substantial threat to island ecosystems in Australia and worldwide. A better understanding of weed distributions is necessary to more effectively manage natural resources on islands. To address this for Western Australian islands, we assembled a database of all available records of alien plants on these islands. In the second paper in this series, we report on the distribution of records from all islands located along the west coast of Western Australia. We defined the west coast as the coastline within the boundaries of the South West, Swan and Midwest regions of the Department of Parks and Wildlife. This area of coastline stretches from Black Point (near Cape Leeuwin) in the south, to Waroora Station (near Coral Bay) in the north. From 4049 individual records, a total of 317 alien plant species were recorded on the 206 islands with existing weed records. A disproportionately large number of weed species were recorded on islands near Perth, estuarine islands, and islands with a history of intensive human activity. Some of the species recorded as present on the islands are known to be serious environmental weeds, including mother of millions (Bryophyllum delagoense), sea spurge (Euphorbia paralias), cleavers (Galium aparine), African boxthorn (Lycium ferocissimum), tree mallow (Malva arborea), ice plant (Mesembryanthemum crystallinum), common prickly pear (Opuntia stricta), sea spinach (Tetragonia decumbens), and golden crownbeard (Verbesina encelioides). The development of management plans to address these species and the survey of islands adjacent to known infestations should be conservation priorities for the west coast islands. Improved biosecurity procedures and enforcement could prevent the establishment of new weed populations on islands and reduce the future costs associated with the management of infestations. [ABSTRACT FROM AUTHOR]