ABSTRACTTo cope with future changing climates, it is paramount to not only breed for heat‐tolerant germplasm but also test the heat tolerance of crops in reliable field‐based experiments for commercial adoption of the research. There is little published research assessing the day‐time heat stress in canola during the optimal growing period under field conditions. Additionally, the impact of heat stress and its interaction with water availability at critical reproductive growth stages appears severely understudied in field experiments. Therefore, a novel system for simulating heat stress was specifically developed and tested for canola plots. Eight portable heat chambers were constructed with clear polycarbonate sheets, fitted with two fan heaters and a ceiling fan that were controlled by a commercial thermostat. Heat stress of 33°C was simulated as heat waves for the eight‐day period during key reproductive stages (start of flowering, mid‐flowering, end of flowering, and late‐podding). The heating system was able to elevate and maintain high temperature consistently across water regimes, validating the system's successful imposition of heat stress. The impact of heat stress was confirmed through a statistically significant plot grain yield reduction that was associated with a reduction in total pods, fertile pods, and seed number. Averaged across different water regimes, heat stress at advanced reproductive developmental stages resulted in grain yield reduction ranging from 39.9% at mid‐flowering to 56.2% at the end of flowering compared to the non‐stressed control. While the system and methodology developed are successful in canola heat tolerance breeding programs, there is potential that this methodology is scalable to other crops or plants.

ABSTRACTDrought‐induced osmotic stress reduces the growth and yield of bread wheat (Triticum aestivum L.) worldwide. Several genotypes of its wild relative, goatgrass (Aegilops biuncialis Vis.) are often tolerant to environmental stresses and used as a gene source for wheat improvement. The Aegilops accessions Ae.b. 382 and Ae.b. 642 collected from contrasted agroecological habitats may represent different defence mechanisms to osmotic stress compared to three bread wheat genotypes with various drought tolerances. The effect of a 1‐week 15% polyethylene glycol (PEG) treatment on various physiological and biochemical parameters was compared at the 2‐leaf stage. The osmotic stress‐induced reduction in shoot length and fresh weight in all genotypes except for Ae.b. 382. This tolerance of Ae.b. 382 can derive from the greater PEG‐induced accumulation of the antioxidant hydroxymethyl‐glutathione in the shoots compared to other genotypes. It is due to an elevated synthesis of its precursors, cysteine and gamma‐glutamylcysteine. In addition, the level of oxidative stress was smaller in Aegilops biuncialis genotypes, shown by the decrease in H2O2 and GSSG levels in roots and shoots, respectively. The amount of gamma‐glutamylcysteine was greater in their roots than in the wheat genotypes. Furthermore, PEG treatment resulted in a greater level of putrescine, as well as the expression of defence‐related genes encoding Glutathione Reductase (GR), cold‐regulated protein Wcor and DihydroFlavonol‐4‐Reductase (DFR) in the shoots of both Aegilops accessions compared to the three wheat genotypes. Based on these differences, certain Aegilops genotypes may serve as a genetic source for the improvement of the stress tolerance of bread wheat.

ABSTRACTRoot system architecture (RSA) is crucial to plant adaptation and the efficiency of soil resource acquisition. However, the RSA variation in okra remains fundamentally uncharacterised. This study aimed to fill this knowledge gap by investigating genetic variability, heritability, and trait associations of RSA characteristics across sixty okra genotypes using a rhizobox‐based phenotyping system that evaluated over 30 RSA traits. There was genotypic variation with coefficients of variation ranging from 5% to 70%. Most traits (76%) demonstrated high broad‐sense heritability (> 60%), particularly those important for capturing soil resources, including total root length, surface area, and volume. Genetic and phenotypic coefficients of variation were predominantly intermediate (10%–20%) to high (> 20%), except for lateral root angle and primary root length, which showed low variation (< 10%). The first four principal components explained 81.7% of the total genotypic variation, with root perimeter, surface area, and volume as the primary contributors to the diversity in the RSA. There were two genotype groups with contrasting RSA ideotypes independent of the geographical origin of the germplasm. There were moderate to very strong, significant positive associations among many RSA and biomass traits (r = 0.51–0.99; p < 0.001). However, the mean root diameter exhibited weak negative but non‐significant correlations with several characteristics. Notable genotypes were identified for specific RSA traits: VI063895 (0.39 and 0.40 g), VI060692 (0.32 and 0.33 g), and GH154 (0.30 and 0.34 g) for superior root biomass allocation; GH108 (2032.28 and 1895.14 cm) for maximum root length; GH111 (25.14 and 20.80 cm3), GH121 (23.56 and 24.59 cm3), and GH157 (18.54 and 19.06 cm3) for enhanced root volume; VI060691 (60° and 62°) and GH125 (61° and 59°) for steep lateral root angles; and V1063895 (10,899 and 10,873), GH135 (9464 and 9330) and GH102 (9303 and 9441) for branching architecture across the two trials. This study advances our understanding of okra RSA diversity, laying the groundwork for trait‐based breeding strategies that enhance adaptation to resource‐limited environments. The identified genotypes represent diverse RSA ideotypes that offer the potential for improving nutrient and water use efficiency.

ABSTRACTMiscanthus is a promising perennial lignocellulosic crop for biomass production. To avoid competing with arable land used for food crops to promote carbon neutrality, cultivating Miscanthus on marginal land, especially in saline soils in China, is a recommended strategy. However, the adaptability of Miscanthus species in saline soil remains largely unknown. In this study, a total of 354 genotypes, including Miscanthus sinensis, Miscanthus floridulus, Miscanthus sacchariflorus, Miscanthus lutarioriparius and interspecific species hybrids derived from M. sinensis and M. lutarioriparius, were evaluated under different planting times (May and August), salinity levels (low and moderate) and pest damage assessment by Helicoverpa armigera in the Yellow River Delta (YRD), in China. The significant effects of planting time on the adaptability of Miscanthus were observed. Planting in May in the YRD, Miscanthus had a lower establishment survival rate (28.76%) and overwintering rate (72.31%), but a dry weight higher than that of planting in August. In contrast, planting in August in the YRD had a very high establishment survival rate (91.14%) and overwintering rate (80.65%), which indicated August was the optimal month for planting Miscanthus in the YRD, while May could be suitable for screening salinity tolerance in Miscanthus. In addition, using the overall adaptability score calculated by establishment survival, overwintering ability, key agronomic traits and pest damage assessments to evaluate all genotypes in this study indicated that the adaptability of M. lutarioriparius was superior to other species. However, M. lutarioriparius is more sensitive to pest damage than others. Furthermore, interspecific hybrids in Miscanthus exhibited outstanding biomass production and adaptability in this region, indicating that creating hybrids would be the best breeding strategy for marginal lands. These results provide an important theoretical basis for the development of Miscanthus in saline soil in the YRD, China.

ABSTRACTIn the relay intercropping of maize and sweet potato, maize brought 40–70 days of shading stress on sweet potato; thus, sweet potato yield was reduced. Morphological and physiological impacts of weak light or shading stress on sweet potato in the early stage are not known. We hypothesised that shading stress would change morphogenesis and physiology of sweet potato in the early stage that leads to low yield. To test this hypothesis, we simulated the shading stress using weak light and applied the shade stress onto two sweet potato cultivars, Yushu‐17 and Qianshu‐8. Results showed that 45‐day weak light caused abnormal growth of sweet potato seedlings. The weak light triggered a smaller diameter, longer internodes and extended length of the main vines on both cultivars. The fresh weight of stems and leaves was less than that under normal light. It was also found that weak light promoted the accumulation of proline (Pro) and malondialdehyde (MDA) that influence osmotic status of the vines. Weak light elevated the activities of both superoxide dismutase (SOD) and catalase (CAT). Although weak light enhanced the content of chlorophyll, it inhibited the net photosynthetic rate (Pn) and sucrose phosphate synthase (SPS), and delayed root development. The yield loss was not reversed by resuming normal light after 60 days of weak light. We conclude that weak light in the early stage impedes normal morphogenesis by disturbing osmotic status and adversely impacting antioxidant and photosynthetic enzymes that led to abnormal growth of the main vines and roots, thus causing yield reduction. These findings may explain the negative impact of the shading stress by maize on the yield of sweet potato in the field.

ABSTRACTLeaf morphology and physiology play a crucial and indispensable role in crop growth and development. Alternate wetting and drying irrigation (AWD) is widely applied in the rice irrigation system. However, there are few studies on the response mechanism of leaf characteristics to AWD. In this study, two indica rice cultivars, Yangdao 6 and Yangliangyou 6, were selected, and two irrigation methods, AWD and conventional irrigation (CI), were set up to analyse the response mechanism of leaf morphology and physiology to yield and water use efficiency (WUE) under AWD. The results showed that yield and WUE were significantly increased under AWD. In terms of yield, AWD increased the effective and high‐effective leaf area index (LAI) and specific leaf nitrogen content at the heading stage, improved the photosynthetic rate and promoted the accumulation and transport of photosynthetic assimilates after flowering. In terms of water use efficiency, AWD inhibited ineffective tillering, regulated stomatal characteristics and increased antioxidant enzyme activity and cytokinin levels. Correlation analysis showed that the percentage of productive tillers, NSC translocation amount and remobilisation, LAI, dry matter accumulation, grain–leaf ratio, leaf morphology (leaf length, leaf width) and leaf physiology (activity of antioxidant enzyme, Z + ZR contents, leaf net photosynthesis rate and specific leaf nitrogen contents) were positively correlated to grain yield and WUE. The results indicate that the improved leaf morphology and physiology of rice under AWD contributed to realise the goal of high grain yield and efficient water use.

ABSTRACTRed clover (Trifolium pratense L.) globally is an important pastoral species, used to strengthen pasture mixes and to produce highly nutritious forage. To ensure its continued use and effectiveness, new adaptable cultivars must be developed. Breeders have continuously harnessed diversity to improve the genetic potential of species, and a key part of this is the introduction of new wild germplasm. This material brings an assortment of genetic variation for key morphological traits for crop improvement and adaptation. A row‐column experimental design was used to observe trait responses of 15 red clover populations, including 12 germplasm populations, across 3 years. Thirteen above‐ and below‐ground traits were used to evaluate plant yield, plant persistence and root structure. As expected, the biomass production of most of the 12 wild germplasm populations was low in comparison with the cultivar controls. However, key relationships between root structure and both plant persistence and plant production were identified, with plants having either an expansive or compact root system or a mixture of both. This study explored wild germplasm material and highlights the potential genetic variation available within germplasm collections. As this is one of a few publications that look at both below‐ and above‐ground traits, it also highlights the benefits of finding the right balance between root systems. This includes the need to breed plants that are able to manoeuvre between root systems depending on the growing conditions.