Herbicide-tolerant wheats are preferred for effective weed management. Rapid phenotyping and effective differential dose are vital for the identification of tolerant genotypes among large quantities of genetic resources. A sand-tray system has been developed to enable rapid assessment of metribuzin damage in wheat seedlings. In total, 946 wheat genotypes were evaluated for metribuzin tolerance by using this system under control and metribuzin-treated conditions. SPAD chlorophyll content index (CCI) offered a non-destructive and rapid analysis of leaf chlorophyll content in wheat seedlings. The application rate for 50% reduction in SPAD CCI (I₅₀) was 3.2-fold higher in the current tolerant genotype (Eagle Rock) than the susceptible genotype Spear. A confirmed dose of 800 g a.i. ha^–1 could differentiate between metribuzin-tolerant and -susceptible lines. The experimental design with two-directional blocking followed by statistical analysis to model the spatial variation was instrumental in selecting potential tolerant or susceptible genotypes. Metribuzin reduced chlorophyll by 51.4% in treated seedlings. The overall adjusted mean SPAD CCI ranged from 13.5 to 42.7 for control (untreated) plants and from 0.1 to 29.9 for treated plants. Through repeated validation, nine genotypes had higher chlorophyll content after metribuzin treatment and significantly (P < 0.05) outperformed the tolerant Eagle Rock, whereas 18 genotypes had significantly (P < 0.05) higher chlorophyll reduction than the susceptible Spear. The top five tolerant and susceptible genotypes were selected for a genetic study of metribuzin tolerance. Domesticated forms of tetraploid and hexaploid wheats had higher tolerance to metribuzin, which suggests that the level of domestication and higher ploidy level contributes to metribuzin tolerance. The new sources of tolerance will accelerate breeding for metribuzin tolerance.

In common wheat (Triticum aestivum L.) and its relative species, considerable progress has been made in understanding the structure and function of the high-molecular-weight glutenin subunit (HMW-GS). As a species closely related to wheat, Aegilops umbellulata is an important resource for wheat genetic improvement. In this paper, we report a novel HMW-GS 1Ux3.5 in Aegilops umbellulata Y361. The complete open reading frame (ORF) coding for 1Ux3.5 was cloned and sequenced. Analysis of the deduced amino acid sequence revealed that the primary structure of 1Ux3.5 was similar to those of previously published HMW-GSs. The 1Ux3.5 possessed an extra cysteine residue in the repetitive domain, indicating that the subunit may be related to excellent dough quality. Subsequently, the single proteins of 1Ux3.5 and 1Dx5 (used as positive control) were purified at a scale sufficient for incorporation into flour for a dough quality test. Both the SDS sedimentation volume and mixograph parameters demonstrated that 1Ux3.5 showed a greater contribution to the dough quality than 1Dx5. Therefore, the 1Ux3.5 subunit from Aegilops umbellulata may have potential value in improving the processing properties of hexaploid wheat varieties.

Organic acids exuded from plant roots significantly modify uptake and long-distance translocation of metals. Little is known about the effect of amino acids on metal ion uptake by plant roots. The present study investigated the effects of exogenous amino acids (histidine and glycine) in a nutrient solution on root uptake and xylem sap transport of cadmium (Cd) in triticale (× Triticosecale cv. Elinor) and bread wheat (Triticum aestivum L. cv. Back Cross Rushan). Plant seedlings were grown in a Cd-free modified Hoagland nutrient solution to which 1 µm Cd was added with either 50 µm histidine or 50 µm glycine or without amino acids at 4 weeks after germination. A control treatment consisted of a nutrient solution free of Cd and amino acids. In bread wheat, addition of histidine to the Cd-containing nutrient solution resulted in a higher operationally defined symplastic Cd fraction but a lower apoplastic one in the roots. In triticale, addition of either amino acid decreased the symplastic Cd fraction but increased the apoplastic one. Addition of histidine to the nutrient solution increased Cd concentration in wheat xylem sap but had no significant effect on Cd concentration in triticale xylem sap. Compared with the Cd-only treatment, the glycine-containing treatment led to significantly reduced Cd concentrations in xylem sap of both plant species. Wheat plants supplied with histidine and Cd accumulated greater amounts of Cd in their shoots than those supplied with Cd alone. Glycine had no significant effects on the Cd content of wheat shoots but decreased it in triticale shoots. Results indicate that the effects of amino acids on plant root uptake and xylem sap translocation of Cd depend on the type of amino acid supplemented. This finding is of great importance for selecting and/or breeding cultivars with Cd-toxicity tolerance.

Cultivation of rice, a globally important cereal crop, is a major cause of emission of the greenhouse gas (GHG) methane (CH₄), giving rise to global warming. Physiological and anatomical characteristics of rice plants associated with CH₄ emission were studied in six high-yielding rice varieties, Dikhow, Dishang, Jaya, Kolong, Kopilee and Lachit, during the pre-monsoon season (April–August) for 2 years (2013 and 2014) in a tropical climate in India. Significant differences (P < 0.001) in photosynthetic rate among the rice varieties were recorded and were found to influence CH₄ emission from the ecosystem. Rate of CH₄ emission was found correlated (r = 0.942) with size of the xylem vessels of the node of the varieties. Kolong, Lachit and Dikhow were identified as low CH₄ emitters with smaller xylem vessels. The recorded GHG intensity (GHGI) revealed rice varieties as a source of GHGs, and among the varieties, Kopilee as a major source of CH₄, with GHGI of 0.083 and 0.093 during 2013 and 2014, respectively. Results suggest that selection of suitable rice varieties with high grain yield accompanied by lower rate of CH₄ emission can be a viable option for reduction of CH₄ emissions from rice agriculture.

Xanthomonas oryzae pv. oryzae (Xoo) is the causal agent of bacterial blight of rice, one of the most devastating rice diseases. We analysed the time-resolved transcriptional expression of aminoacyl-tRNA synthetase (aaRS) genes in Xoo cells treated with rice-leaf extract. Most aaRS genes showed decreased expression in the initial 30 min and recovered or increased expression in the later 30 min. The protein-synthetic machinery of bacterial cells is an important target for developing antibiotic agents; aaRSs play an essential role in peptide synthesis by attaching amino acids onto the corresponding tRNA. In bacteria, glutaminyl-tRNA (Gln-tRNA^Gln) is synthesised in two steps by glutamyl-tRNA synthetase (GluRS) and tRNA-dependent aminotransferase, the indirect biosynthetic mechanism of which is not present in eukaryotes. We determined the crystal structure of GluRS from Xoo (XoGluRS) at resolution of 3.0 Å, this being the first GluRS structure from a plant pathogen such as Xoo. The XoGluRS structure consists of five domains, which are conserved in other bacterial GluRS structures. In the bacterial GluRS structures, the Rossmann-fold catalytic domain and the stem-contact domain are most conserved in both sequence and structure. The anticodon-binding domain 1 is less conserved in sequence but overall structure is conserved. The connective-polypeptide domain and the anticodon-binding domain 2 show various conformations in structure. The XoGluRS structure could provide useful information to develop a new pesticide against Xoo and bacterial blight.

Short-season grain legumes play an important role in smallholder farming systems as source of food and to improve soil fertility through nitrogen fixation. However, it is not clearly understood how these diverse legumes contribute to the resilience of such systems in semi-arid environments. We describe the growth, development and resource-use efficiency (focusing on radiation, RUE) of three promising short-season grain legumes: common bean (Phaseolus vulgaris L.), cowpea (Vigna unguiculata (L.) Walp.) and lablab (Lablab purpureus (L.) Sweet). Two field experiments were conducted during the short rains of 2012–13 and 2013–14 in Eastern Kenya. In the first experiment, the legumes were grown at three plant densities (low, medium, high); in the second experiment, they were subjected to three water regimes (rainfed, partly irrigated, fully irrigated). Phenological development was monitored and biomass accumulation, leaf area index and fractional radiation interception were measured repeatedly during growth; grain yield was measured at maturity. Harvest index and RUE were calculated from these data. Common bean had the shortest growing period (70 days), the most compact growth habit and relatively high RUE but limited grain yield (1000–1900 kg ha^–1), thereby proving more suitable for cultivation in areas with restricted cropping windows or in intercropping systems. Cowpea had a longer growing period (90 days) and a spreading growth habit leading to high light interception and outstanding grain yields under optimal conditions (1400–3050 kg ha^–1). Lablab showed stable RUE values (0.76–0.92 g MJ^–1), was relatively unaffected by limited water availability and had a comparatively long growing period (100 days). Lablab grain yields of ∼1200–2350 kg ha^–1 were obtained across all water regimes, indicating a high potential to cushion climatic variability. Planting density strongly influenced the production success of cowpea and lablab, with high plant densities leading to vigorous growth habit with low podset establishment. Such information on temporal and spatial differences in growth, development and resource-use efficiency is highly valuable for crop-modelling applications and for designing more resilient farming systems with short-season grain legumes.

In order to understanding proteomic basis of drought tolerance in sunflower (Helianthus annuus L.), two contrasting inbred lines were subjected to drought stress during the flowering stage for two years. Proteins were extracted from leaves of well-watered and drought-treated plants by using the TCA–acetone precipitation method and analysed by two-dimensional polyacrylamide gel electrophoresis followed by nanoscale liquid chromatography coupled to tandem mass spectrometry for identification of affected proteins. When comparing proteomic patterns, 18 proteins were changed by drought stress in sensitive lines and 24 proteins in tolerant lines. Concurrent down-expressions of oxygen-evolving enhancer and ferredoxin-NADP reductase were considered as primary drought sensors that mediate downstream pathways to cope with drought conditions. Differential and line-specific proteomic changes were attributed as the source for contrasting response to drought stress. According to the results, scavenging of reactive oxygen species, conservation of energy and water, and cell-structure integrity constituted the major aspects of drought tolerance in sunflower.

A recent rapid change in the cotton harvesting system has increased the risk of soil compaction within the cotton industry with the inception of the John Deere 7760 cotton harvester, a round-bale module builder that weighs >36 Mg. This project involved a novel approach to reducing the risk of soil compaction, whereby cotton defoliation was delayed at times of high field moisture so that the evapotranspiration demands of the crop could be used to dry down the soil profile and consequently reduce the compaction risk at harvest. A field trial at Aubigny, Queensland, was used to evaluate the merit of the proposed management strategy in the 2014–15 growing season, in conjunction with a modelling approach to assess the long-term effectiveness of the strategy in several Australian cotton-growing regions. Although the proposed strategy did reduce the compaction risk, the risk reduction was insufficient for the strategy to be deemed effective. Nonetheless, a strong correlation was found between small changes in soil moisture and changes in observable compaction. An observed 10% increase in soil bulk density after traffic suggested damage to soil pore networks. Furthermore, the depth of compaction was observed well beyond the feasible cultivation depth (to 80 cm).

Water deficit is an environmental constraint restricting plant growth and productivity, and is further worsened by reduced soil fertility. Plant growth-regulating substances ameliorate damaging effects of abiotic stresses, and their efficacy is improved by application of adequate nutrients. An experiment was undertaken to investigate the influence of foliar-applied nutrients (nitrogen, phosphorus, potassium: NPK) and 5-aminolevulinic acid (ALA) alone and in combination on morpho-physiological indices of the perennial grass Leymus chinensis (Trin.) Tzvel under drought and well-watered conditions. Drought stress caused a reduction in growth and photosynthetic pigments while increasing the accumulation of malondialdehyde (MDA) and osmolytes compared with well-watered conditions. However, application of NPK and ALA improved plant height, fresh and dry weights, and chlorophyll content. Production of soluble proteins and sugars, proline content, and antioxidant enzyme activities (superoxide dismutase, peroxidase, catalase, ascorbate peroxidase and glutathione reductase) were increased and MDA accumulation was lowered by application of NPK and ALA relative to the control (no application). Combined application of NPK and ALA proved more advantageous than NPK or ALA alone in exerting ameliorative effect on L. chinensis under drought-stressed conditions. The results suggest that combined application of NPK and ALA improves the growth and development of L. chinensis by modulating physiological processes and aids in sustaining drought.

Four halophytic perennial forage grass species, Distichlis spicata, Paspalum vaginatum, Sporobolus virginicus and S. arabicus, were planted in three salt-degraded and abandoned farms at Mezaira’a, Madinat Zayed and Ghayathi in the United Arab Emirates. The salinity of the irrigation water in the three farms at the time of establishment of the grasses ranged between 14.1 and 17.4 dS m^–1. The productivity of the grasses was assessed over 3 years (2012–14) by harvesting three times per year. Averaged over locations and species, dry biomass yields of the four grasses ranged between 32.64 and 40.68 t ha^–1 year^–1. Sporobolus virginicus produced highest biomass yields, followed by D. spicata, P. vaginatum and S. arabicus, although differences among the four grasses were marginal. In Madinat Zayed and Ghayathi, the average respective forage yields in terms of water productivity were estimated to be 1.68 and 2.42 kg dry matter m^–3 water, better than the reported yield of the traditionally cultivated Rhodes grass (Chloris gayana) from less saline conditions. The study showed that the four halophytic grasses have the potential to contribute to rationalised use of scarce water resources for forage production, besides providing options for enhancing domestic forage production through rehabilitating the salt-affected farms that are unproductive for conventional crops.

A growth-cabinet study was conducted to determine the optimum temperature range for seedling emergence of seven tropical grasses commonly sown in the frost-prone, summer-dominant rainfall region of inland northern New South Wales. The grasses were Bothriochloa bladhii subsp. glabra (forest bluegrass) cv. Swann, Bothriochloa insculpta (creeping bluegrass) cv. Bisset, Chloris gayana (Rhodes grass) cv. Katambora, Digitaria eriantha (digit grass) cv. Premier, Panicum coloratum var. makarikariense (makarikari grass) cv. Bambatsi, and Megathyrsus maximus (panic) cvv. Gatton and Megamax 059. Six constant temperatures were used, ranging from 10°C to 35°C in 5°C increments. Katambora Rhodes grass was the only grass to emerge at 10°C; seedlings of all grasses emerged at temperatures >10°C. Optimal temperature range for emergence varied between species, falling into three groups: low (Bisset creeping bluegrass 16−22°C); intermediate (Premier digit grass 21−32°C, Swann forest bluegrass 23−31°C, Megamax 059 panic 23−35°C, Gatton panic 24−32°C); and high (Bambatsi makarikari grass 24−35°C, Katambora Rhodes grass 24−35°C). The temperature range at which 50% of optimum emergence occurred was 12−14°C for Katambora Rhodes grass, Bisset creeping blue and Premier digit, and 17−18°C for the panic grasses, Swann forest bluegrass and Bambatsi makarikari grass. These temperatures provide options for sowing earlier in spring or later in summer–autumn and may assist development of sowing time options in new environments and provide insight into competition between species.