Lucerne (alfalfa, Medicago sativa L.) is a forage legume that is widely cultivated in arid and semi-arid regions of the world. The main aim of this review was to highlight the effects of salt stress on the performance of lucerne and to suggest different tolerance mechanisms and management strategies for improving its yield under salt stress. Salt stress significantly affects seed germination, carbon fixation, light harvesting, biological N₂ fixation, mineral uptake and assimilation and dry-matter accumulation in lucerne. Accumulation of osmolytes or compatible solutes such as proline, polyamines, trehalose and soluble sugars confers salt tolerance in lucerne. Maintenance of low Na⁺ : K⁺ ratios, antioxidant enzyme activation, and hormonal regulation also help lucerne to withstand salt stress. The screening of diverse genotypes on the basis of germination indices, gas exchange, biomass production, lipid peroxidation and antioxidant enzymes might be useful for breeding salt-tolerant lucerne genotypes. Novel biotechnological tools and functional genomics used to identify salt-conferring genes and quantitative trait loci will help to improve salt tolerance. Use of rhizobial and non-rhizobial plant growth-promoting bacteria, arbuscular mycorrhizal fungi, exogenous application of osmoprotectants, and seed priming with brassinolide, gibberellic acid and salicylic acid may help to improve lucerne performance in saline environments.

Aluminum (Al) toxicity is one of the major environmental constraints to crop production in acidic soils. The objective of this study was to map quantitative trait loci (QTLs) of yield-related traits associated with tolerance to Al in wheat (Triticum aestivum L.). A recombinant inbred line population of wheat was evaluated under conditions of 800 µm aluminum chloride hexahydrate (AlCL₃.6H₂O) at tillering, stem-elongation and flowering stages. Single-locus analysis showed that 22 of 79 QTLs identified were putative. These QTLs explained 4.38–12.24% of the total variation of traits in two growing seasons. Based on two-locus analysis, 71 additive and 11 epistatic QTLs were identified, of which 34 additive and three epistatic QTLs had significant interaction with environmental effects. The greatest number of stable QTLs was related to the A genome. Stable QTLs associated with days to heading and grain yield, with no additive × environment interactions, were co-located with Al concentration (on the 2D linkage group) and 1000-grain weight (on the 6B linkage group). The markers linked to major and stable QTLs identified in the present study can be further assessed in other genetic backgrounds and environmental conditions in order to improve marker-assisted selection and Al tolerance in wheat.

The succession of main-season soybean (Glycine max (L.) Merr.) with off-season maize (Zea mays L.) is an important Brazilian agricultural system contributing to increased grain production without the need for crop land expansion. Yield-gap studies that identify the main factors threatening these crops are pivotal to increasing food security in Brazil and globally. Therefore, the aim of the present study was to determine, for the soybean–off-season-maize succession, the magnitude of the grain and revenue yield gap (YG) caused by water deficit (YG_W) and suboptimal crop management (YG_M), and to propose strategies for closing these gaps in different Brazilian regions. The ensemble of three previously calibrated and validated models (FAO-AZM, DSSAT and APSIM) was used to estimate yields of soybean and off-season maize for 28 locations in 12 states for a period of 34 years (1980–2013). Water deficit is the biggest problem for soybean and off-season maize crops in the regions of Cocos (state of Bahia), Buritis (Minas Gerais) and Formosa (Goiás), where the YG_W accounted for ∼70% of total YG. The YG_M revealed that locations in the central region of Brazil, mainly in the state of Mato Grosso, presented an opportunity to increase yields of soybean and off-season maize, on average, by 927.5 and 909.6 5 kg ha^–1, respectively. For soybean, YG_M was the main cause of total YG in Brazil, accounting for 51.8%, whereas for maize, YG_W corresponded to 53.8% of the total YG. Our results also showed that the choice of the best sowing date can contribute to reducing soybean YG_W by 34–54% and off-season maize YG_W by 66–89%.

Droughts not only reduce the biomass of sorghum (Sorghum bicolor (L.) Moench) but also increase the risk of hydrogen cyanide (HCN) toxicity to animals, mainly due to increased HCN content in drought-stressed plants. In the present study, the variations of HCN contents in 12 sorghum genotypes (10 sweet sorghum cultivars, one Sudangrass and one forage sorghum) were investigated at jointing, filling and ripening stages under rainfed conditions. Next, three genotypes – one sweet sorghum, one Sudangrass and one forage sorghum – were further selected to elucidate the physiological mechanisms of plant growth regulators (PGRs) (abscisic acid (ABA) and methyl jasmonate (MeJA)) in mitigating the concentrations of HCN in drought-stressed plants in a pot experiment. About 100 µg/L ABA and 100 µg/L MeJA were sprayed separately or together twice on drought-stressed (50 and 75% field water capacity) plant leaf. The drought lasted for 15 days. In the field experiment the HCN content in plants reduced from jointing to filling stages then increased from filling to ripening stages in several cultivars. In the pot experiment, drought increased the HCN accumulation and soluble protein content in leaves of all three genotypes. PGRs overall reduced the HCN contents in drought-stressed sweet sorghum and Sudangrass but not in forage sorghum (except in the ABA+MeJA treatment). However, the soluble protein contents were reduced by PGRs in drought-stressed forage sorghum but not in sweet sorghum (except in the ABA+MeJA treatment) and Sudangrass. Both ABA and MeJA increased the plant weights, whereas only MeJA enhanced net photosynthetic rate (P_N) in all three genotypes. PGRs reduced release rate of superoxide and hydrogen peroxide and malondialdehyde in all drought-stressed plants, and reduced the activities of peroxidase, superoxide dismutase, catalase, and ascorbate peroxidase in sweet sorghum but not in other two genotypes. These results suggest that exogenous ABA and MeJA could increase plant weight and reduce HCN content in drought-stressed sorghums, with varying physiological responsive mechanisms among sorghum genotypes.

Drought stress causes lower crop production globally. Plants have acquired many adaptations to overcome drought stress. Mungbean (Vigna radiata (L.) R.Wilczek) is a legume crop widely cultivated in South, East and Southeast Asia. It is grown in high-temperature areas where drought is the main cause of reduced plant growth and productivity. Plants cope with drought stress by activating different signalling mechanisms. The sucrose non-fermenting-1-related protein kinase 2 family (SnRK2s) is known to play vital roles in osmotic stress and in abscisic acid (ABA) signalling pathways by phosphorylating downstream targets. The genes encoding SnRK2s in mungbean and their detailed characterisation remain unexplored. We have conducted extensive genome-wide analysis for gene prediction, in silico gene analysis, evolutionary analysis and gene-expression profiling under drought-stress conditions by quantitative real-time PCR. Through genome-wide analysis, eight SnRK2 genes were predicted in the mungbean genome and were assigned the names VrSnRK2.1–VrSnRK2.8, according to their order on the chromosomes. The VrSnRK2 genes identified were classified into three clusters based on their phylogenetic relationship with those of Arabidopsis thaliana. Drought stress was imposed on 11-day-old mungbean plants by completely withholding water for 3 days. According to real-time qPCR data, the expression of most of the VrSnRK2 genes was induced by drought stress, indicating their role in the drought-stress response. One of the genes, namely SnRK2.6c, showed highest expression level (12-fold) under drought stress, possibly indicating a critical role under water-deficit conditions. These data provide important information about the VrSnRK2 gene family in mungbean. The results will help in future functional characterisation of VrSnRK2 genes.

Soybean mosaic virus (SMV) is one of the most destructive pathogens of soybean (Glycine max (L.) Merr.) worldwide. In this study, 184 F_7:11 recombinant inbred line (RIL) populations derived from Kefeng No. 1 × Nannong 1138-2 were used to study the inheritance and linkage mapping of resistance genes against SMV strains SC7 and SC13 in Kefeng No. 1. Two independent dominant genes (designated Rsc7 and Rsc13) that control resistance to SC7 and SC13 were located on a molecular linkage group (MLG) of chromosome 2 (D1b). A mixed segregating population was developed by self-pollination of three heterozygous plants of residual heterozygous lines (RHL3-27, RHL3-30, RHL3-53) with five markers linked to the loci, and was used in fine-mapping of Rsc7 and Rsc13. In addition, Rsc7 was fine-mapped between BARCSOYSSR_02_0667 and BARCSOYSSR_02_0670 on MLG D1b. The genetic distance between the two closest markers was 0.7 cM and the physical distance of the interval was ∼77 kb, which included one LRR gene and another gene containing an F-box region. Two SSR markers (BARCSOYSSR_02_0610 and BARCSOYSSR_02_0621) were closely linked to the SC13 resistance gene. The physical distance where Rsc13 was located was ∼191 kb. Sequence analysis showed that there were two K-box region types of transcription factor genes; GmHSP40 and two serine/threonine protein kinase (STK) genes were the most likely candidate genes. These results will facilitate map-based cloning of the Rsc7 and Rsc13 genes and development of transgenic disease-resistant varieties, and will provide SMV-resistance breeding systems with excellent resistance germplasm.

Millions of people have Zn-deficient diets, so Zn-biofortified crops could prevent such deficiency. The aim of this study was to evaluate the use of agronomic Zn biofortification of broccolini – a new hybrid crop variety derived from a cross between kalian cabbage and broccoli. Plants were grown in pots using a Zn deficient soil. Four fertiliser treatments were tested: (1) control; (2) soil application of 5 mg ZnSO₄•7H₂O kg^–1 soil; (3) foliar application at the early flowering stage of 0.5% (w/v) ZnSO₄•7H₂O; (4) combined soil and foliar treatments. Florets were harvested in four sequential harvests. There was a decrease in both growth and leaf composition of Zn, Ca, Fe and Mg. Soil Zn application increased floret production. There were increases in the Zn concentration stem+leaves and florets of 12- and 2.5-fold in foliar and soil+foliar treatments respectively. PA:Zn molar ratios decreased under both foliar and soil+foliar treatments. Boiling reduced Zn concentration by 40%, along with a decrease of other mineral nutrients. A soil+foliar treatment can increase both plant growth and Zn concentration in broccolini, and boiled 100 g portion of biofortified florets fertilised at rates in this study would deliver ∼49 mg Zn, a 46% increase than in the non-biofortified broccolini.

Six years of survey data taken from 184 paddocks spanning 14 million ha of land used for crop and pasture production in south-west Western Australia were used to assess weed populations, herbicide resistance, integrated weed management (IWM) actions and herbicide use patterns in a dryland agricultural system. Key findings were that weed density within crops was low, with 72% of cropping paddocks containing fewer than 10 grass weeds/m² at anthesis. Weed density and herbicide resistance were not correlated, despite the most abundant grass weed species (annual ryegrass, Lolium rigidum Gaudin) testing positive for resistance to at least one herbicide chemistry in 92% of monitored paddocks. A wide range of herbicides were used (369 unique combinations) suggesting that the diversity of herbicide modes of action may be beneficial for reducing further development of herbicide resistance. However, there was a heavy reliance on glyphosate, the most commonly applied active ingredient. Of concern, in respect to the evolution of glyphosate resistant weeds, was that 45% of glyphosate applications to canola were applied as a single active ingredient and area sown to canola in Western Australia expanded from 0.4 to 1.4 million hectares from 2005 to 2015. In order to minimise the weed seed bank within crops, pastures were used infrequently in some regions and in 50% of cases pastures were actively managed to reduce weed seed set, by applying a non-selective herbicide in spring. The use of non-selective herbicides in this manner also kills pasture plants, consequently self-regenerating pastures were sparse and contained few legumes where cropping intensity was high. Overall, the study indicated that land use selection and utilisation of associated weed management actions were being used successfully to control weeds within the survey area. However, to successfully manage herbicide resistant weeds land use has become less diverse, with pastures utilised less and crops with efficacious weed control options utilised more. Further consideration needs to be given to the impacts of these changes in land use on other production factors, such as soil nutrient status and plant pathogens to assess sustainability of these weed management practices in a wider context.

Increasing the area sown to Ornithopus spp. (serradella) can reduce overall fertiliser requirements in Australian permanent pastures owing to their greater nutrient-acquisition efficiency than that of more widely used pasture legumes such as Trifolium spp. However, uncertainty regarding waterlogging tolerance of Ornithopus spp. may restrict their adoption in the high-rainfall zone of southern Australia. The waterlogging tolerance of cultivars and accessions of three species of Ornithopus (O. compressus, O. sativus and O. pinnatus) was determined by comparing root and shoot growth of plants in deoxygenated, stagnant agar nutrient solution (simulated waterlogging) with growth in aerated nutrient solution. The responses were benchmarked against the known waterlogging-tolerant pasture legume Trifolium michelianum. All Ornithopus cultivars were highly impacted by the deoxygenated stagnant treatment, including those of the anecdotally waterlogging-tolerant O. pinnatus. The 14-day stagnant treatment reduced root dry mass by 32–62% and relative growth rate (RGR) of roots by 36–73%. At the same time, root porosity increased from 1.4% to 8.8%. Following a 14-day recovery period, during which plants were returned to aerated nutrient solution, Ornithopus spp. failed to increase their shoot RGR (particularly for O. sativus cultivars); however, root RGR returned to that of the aerated controls. The stagnant conditions inhibited transport of potassium (K⁺) to the shoots in all species, as evidenced by lower shoot tissue K⁺ concentrations, with O. compressus and O. sativus most adversely affected (45% and 48% of the tissue concentration of aerated control plants). We conclude that the suggested area for Ornithopus spp. adaptation should not preclude areas of high rainfall because they have root adaptations that would assist them in coping with transient water excess; however, soil types and surface profiles conducive to long-term waterlogging should be avoided to negate significant productivity losses.