Leaf colour plays an important role in plant growth and development. In this study, a stably inherited yellow–green leaf mutation, temporarily designated yglw-1, was initially isolated from progenies of wheat (Triticum aestivum L.) cross Bainong58409/Caifumai. The yellow-leaf phenotype could be observed in the yglw-1 mutant during the seedling stage, and then the yellow leaves gradually progressed from the bottom to the top throughout development. Compared with its sister line Cf5019-21 with a normal leaf-colour phenotype, the main agronomic traits of the yglw-1 mutant including spike length, number of kernels per spike and 1000-kernel weight were significantly decreased. Measurement of chlorophyll contents showed that chlorophylls a and b in the third top leaf at the jointing stage and the penultimate leaf and third top leaf at the heading stage were obviously lower in yglw-1 than in Cf5019-21. Genetic analysis indicated that the yellow–green leaf trait was controlled by a single recessive gene. Bulked segregant analysis found that two published simple sequence repeat (SSR) markers and four expressed sequence tag-sequence tagged site (EST-STS) markers were linked to the yglw-1 gene, and BE494262 was the most closely linked marker to yglw-1, at a genetic distance of 2.3 cM. To increase the density of the genetic map, 135 novel SSR markers at a certain distance near the marker BE494262 were developed according to SSR loci detected in the Chinese Spring reference sequence. Of these, nine SSR markers detected polymorphic fragments between the two parents as well as between the contrasting DNA bulks. Finally, the yglw-1 gene was mapped between SSR markers Xhwm1 and Xhwm43 and showed genetic distances 1.9 cM and 23.9 cM on chromosome 2BS. These findings can facilitate candidate-gene prediction and map-based cloning of the yglw-1 gene.

Aphids are economically important pests of cereal crops globally. They feed on the sap of plants, which can directly reduce yield and grain quality. Many species are also proficient at transmitting important plant viruses. Two of the world’s most damaging cereal aphids are the Russian wheat aphid (Diuraphis noxia) and bird cherry oat aphid (Rhopalosiphum padi). These species are present in all major grain-growing regions worldwide, with D. noxia recently invading Australia. In many countries, including Australia, chemicals are an important control option. Insecticide seed-dressings, in particular, are widely used to combat early-season infestations of aphids in establishing cereal crops. In this study we examined the length of protection provided by several insecticide seed-dressings against D. noxia in wheat, and compared this with R. padi. All seed-dressings examined were efficacious for up to 5 weeks after wheat emergence; however, notable differences were evident between aphid species. In most instances, R. padi was able to persist and reproduce on wheat at an earlier growth stage than D. noxia. These findings suggest that R. padi is more tolerant to certain insecticides and may therefore re-infest insecticide-treated wheat fields earlier than D. noxia.

The aim of this work was to analyse and compare indigenous arbuscular mycorrhizal colonisation (AMC) in relation to growth and total soluble carbohydrates (TSC) in two major, physiologically contrasting crop species: maize (Zea mays L.) and sunflower (Helianthus annuus L.). In order to promote contrasting TSC concentrations, we modified the radiation source by shading and the carbohydrate sink by manipulating reproductive sinks at different phenological stages during the grain-filling period in two field experiments. We assessed plant dry matter, TSC in stems, and root AMC from flowering until final harvest. AMC during the grain-filling period decreased in maize and increased in sunflower. A sink limitation increased AMC in maize, and reduced it in sunflower. A source limitation decreased AMC in both species, especially in sunflower. AMC was positively related to TSC in maize, but negatively in sunflower. The relationship was affected by shading in sunflower, but not in maize. In both species, a different linear model described the relationship between AMC and TSC in plants submitted to the removal of the reproductive organs. The results highlight the role of carbohydrates in mediating mycorrhizal formation, and show for the first time the opposite AMC–TSC relationships in maize and sunflower.

A 2-week road trip was made through the Pilbara region to collect seed of native Vigna species. Thirty-two new accessions were collected, all of which were within what can be broadly described as the V. lanceolata Benth. complex. All 32 accessions were amphicarpic, rhizomatous, trailing or vining perennials. The largest and most widely distributed group of 21 accessions belonged to the Silverleaf morphotype and a further nine accessions belonged to the Central morphotype. Two accessions from the Karratha region were of a recently described diminutive species, V. triodiophila. The Silverleaf accessions were all collected from grassy woodlands on river levees and alluvial floodplains. The Central accessions were collected from a more diverse range of habitats, albeit again mostly in wetter or ‘run-on’ parts of the landscape. Measurements of selected traits on a subset of accessions grown for seed increase in Townsville indicated that the Pilbara Silverleaf and Central accessions were comparable with accessions of these morphotypes from elsewhere in northern Australia. Healthy, viable F₁ hybrids were readily obtained from crosses between accessions from all three Vigna groups collected from the Pilbara, indicating that all belong to same primary gene pool. This includes V. triodiophila, notwithstanding its taxonomy. Healthy, viable and fertile F₁ hybrids were also obtained between the Pilbara accessions of both the Silverleaf and Central morphotypes and respective accessions of these morphotypes from elsewhere in northern Australia. The F₁ hybrids between V. triodiophila and both the Silverleaf and the Central accessions exhibited near-normal plant phenotype in terms of the size of their vegetative and reproductive structures, indicating that the diminutive size of V. triodiophila is a recessive trait. The most plausible explanation is that V. triodiophila is a dwarf variant of the Central morphotype, which it most closely resembles apart from its size. The fact that the F₁ hybrids between V. triodiophila and two Pilbara Central accessions were fully self-fertile supports that conclusion, while the recovery of dwarf segregants from small numbers of F₂ and backcross progeny from one of the crosses indicates that the dwarf trait may involve just a single gene. These 32 new accessions extend the range of climatic and edaphic environments, especially at the harsher end, from which accessions of V. lanceolata have been collected and seeds conserved.

The narrow genetic base of lentil (Lens culinaris) has challenged the efforts of breeders to increase its productivity under changing environmental conditions. Inclusion of wild species and diverse cultivated genotypes offers an opportunity to generate new variation through wide hybridisation to broaden the genetic base of cultivated lentil. We evaluated 96 elite, interspecific (L. culinaris × L. orientalis) and intraspecific advanced lentil genotypes along with four checks to determine the extent of genetic variation, resistance to lentil rust (Uromyces viciae-fabae), and the nature and magnitude of their genetic divergence. Sufficient genetic variability was revealed for all of the traits. High heritability and genetic advance were recorded for number of seeds per pod, number of pods per plant, seed yield per plant and biomass per plant. A positive correlation was recorded between grain yield and ten important plant traits. Statistical (D²) and molecular analyses grouped all genotypes into two main clusters and revealed sufficient genetic diversity among advanced lines. Our study showed promising results for creating new variation through wide hybridisation and identified lines L-354 and L-437-1 (rust-resistant) and HPLL-32 (moderately rust-resistant) superior for seed yield and related traits.

Mungbean (Vigna radiata L.) is a valuable legume crop grown in tropical and subtropical areas of Asia. Drought is one of the major factors hindering its growth globally. APETALA2/ethylene-responsive element factor binding proteins (AP2/ERF) are an important family of plant-specific transcription factors (TFs) involved in drought-stress tolerance. We identified 71 AP2/ERF TFs in the mungbean genome by using bioinformatics tools and classified them into subfamilies: AP2 (16 members), ERF (22), RAV (2), DREB (30) and soloist (other proteins with no domain, 1). Members of DREB play a critical role in drought-stress tolerance. Ten-day-old mungbean plants cv. AZRI-06 were exposed to drought stress by complete withholding of water for 7 days. Root samples were collected from control and drought-stressed plants, and the expression pattern of 30 identified VrDREB genes was determined by qPCR. Most VrDREB genes exhibited differential expression in response to drought. Five genes (VrDREB5, VrDREB12, VrDREB13, VrDREB22, VrDREB30) were highly expressed under drought stress and might be considered excellent candidates for further functional analysis and for improvement of mungbean drought tolerance.

A deeper understanding of the phytochemical composition of perennial legumes is important for animal nutrition as well as for the development of pharmaceuticals. The present study is an assessment of perennial legumes including clovers (Trifolium pratense L. and T. medium L.), medics (Medicago sativa L. and M. lupulina L.), sainfoin (Onobrychis viciifolia Scop.) and milkvetches (Astragalus glycyphyllos L. and A. cicer L.) as potential sources of bioactive compounds. Whole aerial parts of plants at stem elongation and full-flowering stages as well as morphological parts of fully flowering plants (leaves, stems and flowers) were analysed for four isoflavones (biochanin A, daidzein, formononetin, and genistein), coumestrol, condensed tannins and triterpene saponins. According to total concentration of the four isoflavones in plants, the species were ranked as follows: T. medium (23.2–28.7 mg g^–1 DM) > T. pratense > A. glycyphyllos = A. cicer = O. viciifolia = M. sativa = M. lupulina (0.054–0.212 mg g^–1 DM). Young plants were 1.2–5.6-fold richer in isoflavones than fully flowering plants. Quantifiable concentrations of coumestrol and saponins were found in the Medicago species and tannins in O. viciifolia. In general, leaves contained the highest concentrations of the phytochemicals. These findings suggest considerable potential to improve legume-based forage quality through appropriate exploitation of species- or cultivar-specific phytochemicals and manipulation of the content of phytochemicals by management of production including growth stage at harvest and selection of plant species.

Acidic conditions with damaging levels of available aluminium (Al³ ) currently limit lucerne (Medicago sativa) production on soils in the New Zealand high country and in large areas of Australia. Increased lucerne nodulation could be achieved by using an Al³ -tolerant strain of Sinorhizobium meliloti to inoculate an Al³ -tolerant lucerne line. The Al³ tolerance of the current commercial Australasian inoculant strain for lucerne, S. meliloti RRI128, was compared with strain SRDI736, selected in Australia for tolerance to low pH. Four Al³ levels (0, 2, 4 and 8 µm) were created at pH 5.1 in a hydroponic system. The rhizobial strains were evaluated on SARDI AT7, a lucerne line selected for improved growth and nodulation in acidic solution culture with Al³ , and on Stamina 5, a commercial cultivar commonly grown in Australasia. SARDI AT7 when inoculated with strain SRDI736 produced more nodules per plant (3.6 vs 2.4) and had higher nodulation percentage (>80% vs <50%) at all Al³ levels than when inoculated with RRI128. The percentage of nodulated Stamina 5 plants after inoculation with the commercial strain was lower than after inoculation with strain SRDI736 (10–16% vs 25–70%) at all Al³ levels.

The potential of S. meliloti strains SRDI736, SRDI672 and RRI128 and rates of lime to increase lucerne nodulation and dry matter production in soils of low pH (<5.5, in water) and high Al³ (>3 mg kg^–1 soil) was also investigated in a pot trial. Lime had a more consistent effect than inoculant strain for increasing nodulation. At 0.5 and 2 t lime ha^–1, plants inoculated with strains SRDI672 and SRDI736 had more nodules per plant than plants inoculated with the commercial strain. At 4 t lime ha^–1, the number of nodules per plant was highest for all three inoculants, and there were no differences among them. This confirms the importance of lime to increase lucerne nodulation in low-pH, high-Al³ soils. However, where liming is uneconomic or impractical, the results show that it was possible to select rhizobial strains to increase lucerne nodulation in acidic soils with damaging levels of available Al³ .

Tall fescue (Festuca arundinacea Schreb.) is a widely used, cool-season turf grass and is relatively sensitive to water stress. Melatonin has been reported to improve abiotic stress tolerance in many plants. In this study, we demonstrated that, although shoot height and fresh weight of tall fescue seedlings were significantly reduced by drought stress, they were increased by melatonin pre-treatment compared with control plants. Chemical analyses showed that tall fescue seedlings pre-treated with melatonin exhibited decreased levels of reactive oxygen species, electrolyte leakage and malondialdehyde, but higher levels of antioxidant enzyme activities (catalase, and peroxidase) and total chlorophyll content, compared with untreated seedlings. Leaf water loss was also partially mitigated and leaf water content increased by melatonin application, resulting in improved plant growth under drought stress. Moreover, root growth of tall fescue seedlings was promoted by melatonin under osmotic stress. The results show that drought tolerance was improved in cool-season tall fescue by application of exogenous melatonin. Therefore, melatonin may potentially be used as a protectant for plants against the deleterious effects of drought or water-deficit stress.

South African lovegrass (Eragrostis plana Nees) is an aggressive and difficult-to-control species in grazing areas of the south of South America, whose invasion capacity is increased by its phytotoxic capability. The objectives of this work were to identify and quantify chemicals produced by the plant shoots, to evaluate the inhibitory capability of plant extracts on development of lucerne (Medicago sativa L.) and wheat (Triticum aestivum L.), and to determine the spatial distribution of phenolics in rhizosphere soil in an infested field. Extracts were obtained by exhaustive extraction of dry shoot biomass, using solvents in increasing order of polarity. Soil samples contained in the rhizosphere were collected from an infested field. Bioassays for determination of phytotoxicity of extracts on lucerne and wheat seedlings were conducted in a completely randomised design with four replicates. The extracts showed suppressive, stimulating or neutral effects on the development of the radicle, shoots, and total lucerne and wheat seedlings, with greater phytotoxicity, generally, of ethyl acetate and methyl alcohol extracts. In the shoot extracts, nine phenolic compounds were identified and quantified: caffeic acid, coumaric acid, ferulic acid, gallic acid, vanillic acid, catechin, epicatechin, resveratrol, rutin. Of these, four were identified in the soil: catechin, epicatechin, coumaric acid, ferulic acid. Catechin, epicatechin and ferulic acid showed similar distribution patterns in the soil profile, with higher concentrations detected on the surface and on the side opposite the plant crown, which indicates release by the decomposition of tissues deposited on the soil surface. Coumaric acid showed higher concentrations on the surface and in the deeper layer of the soil next to the plant, indicating release both from decomposition of the shoots and from the root system. Future work may explore the phytotoxicity of the analytes identified, either isolated or in admixture, using dose curves and an inhibitory response to target plant species.