Wild relatives of wheat have served as a pool of genetic variation for understanding salinity tolerance mechanisms. Two separate experiments were performed to evaluate the natural diversity in root and shoot Na exclusion and K accumulation, and the activity of four antioxidant enzymes within an extensive collection of ancestral wheat accessions. In the initial screening experiment, salinity stress (300 mm NaCl) significantly increased Na concentration in roots and leaves and led to a significant decline in root and shoot fresh weights, dry weights, and K contents. Principal component analysis of the 181 accessions and 12 species identified three first components accounted for 63.47% and 78.55% of the variation under salinity stress. We identified 12 accessions of each species with superior tolerance to salinity for further assessment of their antioxidant defence systems in response to salinity. Both mild (250 mm NaCl) and severe (350 mm NaCl) levels of salinity significantly increased activities of four enzymes, indicating an enhanced antioxidant-scavenging system for minimising the damaging effects of H₂O₂. Some of the wild relatives—Aegilops speltoides (putative B genome), Ae. caudata (C genome), Ae. cylindrica (DC genome) and Triticum boeoticum (A^b genome)—responded to salinity stress by increasing antioxidants as the dominant mechanism to retain oxidative balance in cells. Further evaluation of salt-tolerance mechanisms in these superior wild relatives will help us to understand the potential of wheat progenitors in the development of more salt-tolerant varieties.

Zinc (Zn) deficiency reduces the grain yield and quality of wheat. Plant-growth-promoting bacteria may help to improve plant Zn availability. This study evaluated the influence of inorganic Zn, with and without Zn-solubilising bacteria (Pseudomonas sp. MN12), on performance and grain biofortification of wheat. Zinc was supplied with and without Pseudomonas to two bread wheat (Triticum aestivum L.) cultivars (Lasani-2008 and Faisalabad-2008) via four treatments: soil application (5.0 mg kg^–1 soil), foliar application (0.025 m), seed priming (0.5 m) and seed coating (1.25 g kg^–1 seed). Hydroprimed seeds were taken as control. Inoculation with Pseudomonas improved photosynthesis, yield, biofortification of grains and organic acid production in root exudates. However, inoculation was more effective when applied in combination with different Zn application methods. Maximum improvement in plant photosynthetic assessment and grain yield was recorded with Pseudomonas Zn seed priming, followed by Pseudomonas soil application of Zn. These two combinations also enhanced organic acid production in root exudates of wheat. Soil and foliar application of Zn with Pseudomonas enhanced Zn concentration in whole grain, embryo, aleurone and endosperm. Combined application of Pseudomonas and Zn (soil and foliar) reduced phytate concentration and [phytate] : [Zn] ratio and increased the bioavailable Zn in wheat grain compared with the control. In conclusion, the combination Pseudomonas inoculation along with Zn seed priming and soil application was more effective in improving grain yield of wheat, whereas soil- and foliar-applied Zn with Pseudomonas inoculation was better in enhancing grain Zn concentration and bioavailability.

Oats likely emerged as part of the weedy grass assemblage in early wheat and barley crops. Some Avena species, such as A. fatua and A. sterilis, evolved into aggressive weeds, and the high interspecific competitive ability of cultivated oats (A. sativa) is valued agronomically to facilitate weed control in rotations. We tested the hypothesis, verified in many crops, that high yield of oats is related to low intraspecific competitive ability. Ten contemporary oat varieties, selected for grain yield and milling attributes, where grown in three environments. Response to competition was calculated as 100 × (Yb – Yc)/Yc, where Y is yield measured in border (b) and centre (c) rows. The same definition was used to calculate response to competition of yield components (biomass, harvest index, grain number, grain weight) and the components of grain number (panicle number and grains per panicle). Yield response to competition was affected by all three sources of variation, i.e. environment, variety and variety × environment interaction. The interaction demonstrates the plasticity of yield response to intraspecific competition; for example, the response to competition of variety Mortlock varied from 9% to 71% among environments. This plasticity in yield response to competition was partially related to variety-dependent responses to competition for biomass and harvest index, number of panicles and number of grains per panicle. We did not find the expected negative association between yield and variety-dependent response to competition. We discuss how this lack of correlation could relate to sampling issues, i.e. a limitation in the range of environments and varieties explored in this study, or reflect a legitimate feature of oat crops arising from early and contemporary selective pressures.

Identifying stable, high-yielding genotypes is essential for food security. This is particularly relevant in the current climate change scenario, which results in increasing occurrence of adverse conditions in the Mediterranean region. The objective of this study was to evaluate stability of barley (Hordeum vulgare L.) grain yield, and its relationship to the duration of the growth cycle and its stability under Mediterranean conditions in Egypt. Nineteen genotypes were evaluated during three growing seasons (2013–14 to 2015–16) at two locations (Elkhatara, Ghazala) and two growing seasons (2014–15 and 2015–16) at a third location (Ras-Sudr), i.e. eight environments (location–year combinations) in total. The linear regression explained a significant 48.2% and 22.8% of GEI variation for days to heading and grain yield, respectively, and the genotypic linear slopes were highly related to the first principal component of the AMMI model. Although all genotypes were well adapted to the region, there were different GEI responses, with changes in ranking across locations. Some stable and broadly adapted genotypes were identified, as well as unstable genotypes with specific adaptations. High yields across environments were attained by very stable (G4, G5), intermediate and stable (G1, G9) and highly responsive (G18, G19) genotypes. In general, responsiveness (b values) of yield and days to heading were negatively correlated, and high yielding genotypes showed different patterns of responses of days to heading. Genotypes G1, G4, G5 and G9 seemed best adapted overall, with longer season genotypes (e.g. G18 and G19) offering prospects to explore other formats of varieties in breeding, particularly for situations of climate instability.

Drought is a devastating environmental stress in agriculture and hence a common target of plant breeding. A review of breeding progress on drought tolerance shows that, to a certain extent, selection for high yield in stress-free conditions indirectly improves yield in water-limiting conditions. The objectives of this study were to (i) assess the genotype × environment (GE) interaction for grain yield (GY) and other agronomic traits for maize (Zea mays L.) across East African agro-ecologies; and (ii) evaluate agronomic performance and stability in Uganda and Tanzania under optimum and random drought conditions. Data were recorded for major agronomic traits. Genotype main effect plus GE (GGE) biplot analysis was used to assess the stability of varieties within various environments and across environments. Combined analysis of variance across optimum moisture and random drought environments indicated that locations, mean-squares for genotypes and GE were significant for most measured traits. The best hybrids, CKDHH1097 and CKDHH1090, gave GY advantages of 23% and 43%, respectively, over the commercial hybrid varieties under both optimum-moisture and random-drought conditions. Across environments, genotypic variance was less than the GE variance for GY. The hybrids derived from doubled-haploid inbred lines produced higher GY and possessed acceptable agronomic traits compared with the commercial hybrids. Hybrid CKDHH1098 ranked second-best under optimum-moisture and drought-stress environments and was the most stable with broad adaptation to both environments. Use of the best doubled-haploids lines in testcross hybrids make-up, well targeted to the production environments, could boost maize production among farmers in East Africa.

This study assessed two versions of the crop model CropSyst (i.e. EMS, existing; MMS, modified) for their ability to simulate maize (Zea mays L.) yield in South Africa. MMS algorithms explicitly account for the impact of extreme weather events (droughts, heat waves, cold shocks, frost) on leaf development and yield formation. The case study of this research was at an experimental station near Johannesburg where both versions of the model were calibrated and validated by using field data collected from 2004 to 2008. The comparison of EMS and MMS showed considerable difference between the two model versions during extreme drought and heat events. MMS improved grain-yield prediction by ∼30% compared with EMS, demonstrating a better ability to capture the behaviour of stressed crops under a range of conditions. MMS also showed a greater variability in response when both versions were forced with scenarios of projected climate change, with increased severity of drought and increased temperature conditions at the horizons 2030 and 2050, which could drive decreased maize yield. Yield was even lower with MMS (8 v. 11 t ha^–1 for EMS) at the horizon 2050, relative to the baseline scenario (∼13 t ha^–1 at the horizon 2000). Modelling solutions accounting for the impact of extreme weather events can be seen as a promising tool for supporting agricultural management strategies and policy decisions in South Africa and globally.

The tensile property of roots is an important factor for anchorage and for resistance to root lodging. In this study, a root tensile test was applied to maize (Zea mays L.) grown in the field at three planting densities, 4.5 × 10⁴, 6.75 × 10⁴ and 9.0 × 10⁴ plants ha^–1, to quantify the maximum tensile force (F_max) and tensile strength (T_s) of roots at the V10 stage (tenth leaf visible) and grain-filling stage. In addition, relationships among tensile properties, diameter and turgid weight : dry weight (TW : DW) ratio of roots were investigated. The results showed that the F_max of primary and seminal adventitious roots was lower than of nodal roots. Among nodal roots, the F_max of roots on upper nodes was higher. Planting density significantly affected the tensile force of nodal roots of the sixth to eighth tiers; their F_max decreased with increasing planting density. A positive linear correlation between F_max and root diameter and a power function between T_s and root diameter was observed. In addition, there was a positive linear correlation between the TW/DW ratio and root diameter and a negative exponential correlation between T_s and TW : DW ratio. Therefore, nodal roots with a lower TW : DW ratio could have a larger T_s, because their cells are smaller and cell walls are thicker. This result suggests that nodal roots with small and thick cells benefit the tensile properties of maize.

Phytosterols are allies in the control of plasma cholesterol and in preventing cardiovascular diseases. As vegetable oils are the main source of phytosterols, characterising environmental factors that determine phytosterols accumulation in the oil is an important objective. The present research focuses on evaluating how intercepted solar radiation (ISR, the main environmental factor affecting oil accumulation) can determine phytosterol accumulation in sunflower oil. The aim of this work was to study the dynamics of phytosterols accumulation under different ISR levels and its relationships with the dynamics of oil accumulation. Two field experiments were conducted with hybrids with different fatty acid composition. Treatments applied during grain filling were: two levels of defoliation (75% and 80%) and a control. A 50% grain thinning treatment was also applied. Oil phytosterols concentration increased with defoliation during grain-filling period, whereas phytosterols content per grain decreased. β-sitosterol and campesterol were the most affected sterols. Reduction in ISR did not affect the rates of phytosterols accumulation. The durations of the accumulation period of these components varied in accordance with the duration of oil accumulation period. These results reinforce the importance of environmental factor in determining oil quality in sunflower grains.

Leucaena (Leucaena leucocephala (Lam.) de Wit subsp. glabrata (Rose) Zarate) in combination with grass pasture is one of the most persistent, productive and sustainable grazing systems used in Queensland, Australia. Nevertheless, a better understanding of the competitive interactions that determine the proportions of leucaena and grass components is needed to optimise the design and management of the hedgerow pasture system. In a water-limited environment, belowground interactions between species are especially influential. Accordingly, the aim of this study was to determine the effect of leucaena plant density and Rhodes grass (Chloris gayana Kunth) competition on root distribution, evapotranspiration, patterns of soil-water use and the resulting water-use efficiency (WUE) of the leucaena and grass components.

Results showed that although leucaena had deeper roots than Rhodes grass, the majority of fine roots of both leucaena and Rhodes grass were in the upper 1.5 m of the soil profile suggesting a high level of competition for water resources. A major factor favouring Rhodes grass was that its root abundance was 8–10 times greater than leucaena, allowing it to compete more effectively for water resources and limit the lateral spread of leucaena roots. Higher cumulative evapotranspiration values were recorded from leucaena grown with Rhodes grass than from leucaena grown in absence of grass. However, this difference was negligible at the highest leucaena density owing to the reduced yield of grass caused by shading and increased water uptake of leucaena. The findings of this study also confirmed the hypothesis that at low tree densities, leucaena–grass pasture will have higher WUE (13.8 kg DM mm^–1) than sole leucaena, but this difference was reduced with increments of leucaena density. Highest WUE (65.9 kg DM mm^–1) occurred at highest leucaena density with or without grass.

The ability to recover from the impact of short-term submergence was assessed on four widely used grasses in pastures: Dactylis glomerata L., Bromus catharticus Vahl., Schedonorus arundinaceus Schreb. (syn. Festuca arundinacea) and Phalaris aquatica L. Six-week-old plants were subjected to a 5-day complete submergence in clear water, followed by a 15-day recovery period. Dry mass after submergence, shoot and root growth, number of tillers per plant, leaf stomatal conductance and leaf greenness during recovery were assessed. Dactylis glomerata and B. catharticus were sensitive to submergence, showing very low relative growth rate (RGR) of shoots and roots during recovery (37–67% lower than controls) along with early leaf senescence and persistent partial stomatal closure. Schedonorus arundinaceus exhibited an intermediate tolerance, sustaining high RGR of shoots (similar to controls) and fully adjusting its leaf functionality during recovery despite being affected during submergence (40% decrease in dry mass and 37% in tiller number). Phalaris aquatica performed outstandingly, with dry mass unaffected by submergence, and unaltered stomatal conductance, leaf greenness, tillering and shoot growth during recovery. Therefore, in areas where flooding can often cause plant submergence, P. aquatica is recommended whereas the other species are not, because they may be outcompeted by flood-tolerant species.