Terminal heat stress has become one of the major threats due to global climate change which is significantly affecting the production and productivity of wheat crop. Therefore, it is necessary to identify key traits and genotypes to breed heat-tolerant wheat. The present study was undertaken with the objective of comparing the effects of heat stress (HSE) and extended heat stress (EHSE) on phenological-physio-biochemical traits of contrasting heat-tolerant and heat-susceptible genotypes during the reproductive phase. Phenological traits exhibited significant reduction under EHSE compared to HSE. Heat-tolerant genotypes maintained balanced phenological-physio-biochemical traits, while heat-sensitive genotypes showed significant reductions under both stress regimes. Among phenological traits, DM (R² = 0.52) and BY (R² = 0.44) have shown a positive effect on seed yield, indicating that biomass and crop duration contributed to the yield advantage under stress. During the grain filling stage, both the normalized difference vegetation index (NDVI) and chlorophyll (Chl) exhibited consistently positive impacts on grain yield under both HSE and EHSE conditions. This could be attributed to the enhanced photosynthesis resulting from delayed senescence and improved assimilate remobilization under terminal heat stress. The biochemical activity of superoxide dismutase (SOD), peroxidase (POX), and ascorbate peroxidase (APX) was induced in tolerant genotypes under HSE. The correlation of canopy temperature with phenological-physio-biochemical traits remained static under HSE and EHSE, suggesting CT as the best selection parameter for heat tolerance. The traits showing a positive association with yield and that are less affected under stress could be used for selecting tolerant genotypes under stress environments. These tolerant genotypes can be used to develop mapping populations to decipher the genes conferring tolerance as well as to study the molecular basis of tolerance.

Climate change has resulted in extreme temperature and drought around the globe, which poses serious threat to food security. Both heat and drought stress affects the production and productivity of wheat crop. The present study was undertaken to evaluate 34 landraces and elite cultivars ofTriticumspp. for phenological and yield-related traits under optimum, heat, and combined heat–drought stress environments during 2020–2021 and 2021–2022. The pooled analysis of variance showed significant genotype × environment interaction, suggesting an influence of stress on trait expression. The trait performance of genotypes exhibited significant reduction under combined heat–drought stress as compared to optimum and heat stress environments. The maximum seed yield penalty was observed under combined heat–drought stress environment as compared to heat stress alone. Regression analysis indicated significant contribution of number of grains per spike towards stress tolerance. Based on Stress Tolerance Index (STI), genotypes Local-17, PDW 274, HI-8802, and HI-8713 were identified to be tolerant to both heat and combined heat and drought stress at Banda, whereas genotypes DBW 187, HI-8777, Raj 4120, and PDW 274 were tolerant at Jhansi location. The genotype PDW 274 showed stress tolerance under all treatments at both the locations. The genotypes PDW 233 and PDW 291 showed highest stress susceptibility index (SSI) across the environments. The number of grains per spike and test kernel weight were positively associated with seed yield across the environments and locations. The selected genotypes Local-17, HI 8802, and PDW 274 were identified to be the potential sources of heat and combined heat–drought tolerance, which may be utilized in hybridization to develop tolerant wheat genotypes and also for mapping of underlying genes/quantitative trait loci (QTLs).

Genome editing technologies provide a powerful tool for genetic improvement of perennial ryegrass, an important forage and turfgrass species worldwide. The sole publication for gene editing in perennial ryegrass used gene-gun for plant transformation and a dual promoter based CRISPR/Cas9 system for editing. However, their editing efficiency was low (5.9% or only one gene-edited plant produced). To test the suitability of the maize Ubiquitin 1 (ZmUbi1) promoter in gene editing of perennial ryegrass, we produced ZmUbi1 promoter:RUBY transgenic plants. We observed that ZmUbi1 promoter was active in callus tissue prior to shoot regeneration, suggesting that the promoter is suitable for Cas9 and sgRNA expression in perennial ryegrass for high-efficiency production of bi-allelic mutant plants. We then used the ZmUbi1 promoter for controlling Cas9 and sgRNA expression in perennial ryegrass. A ribozyme cleavage target site between the Cas9 and sgRNA sequences allowed production of functional Cas9 mRNA and sgRNA after transcription. Using Agrobacterium for genetic transformation, we observed a 29% efficiency for editing the PHYTOENE DESATURASE gene in perennial ryegrass. DNA sequencing analyses revealed that most pds plants contained bi-allelic mutations. These results demonstrate that the expression of a single Cas9 and sgRNA transcript unit controlled by the ZmUbi1 promoter provides a highly efficient system for production of bi-allelic mutants of perennial ryegrass and should also be applicable in other related grass species.

Waterlogging represents a substantial agricultural concern, inducing harmful impacts on crop development and productivity. In the present study, 142 diverse sesame genotypes were examined during the early vegetative phase to assess their response under waterlogging conditions. Based on the severity of symptoms observed, 2 genotypes were classified as highly tolerant, 66 as moderately tolerant, 69 as susceptible, and 5 as highly susceptible. Subsequent investigation focused on four genotypes, i.e., two highly tolerant (JLT-8 and GP-70) and two highly susceptible (R-III-F6 and EC-335003). These genotypes were subjected to incremental stress periods (0 h, 24 h, 48 h, 72 h, and 96 h) to elucidate the biochemical basis of tolerance mechanisms. Each experiment was conducted as a randomized split-plot design with three replications, and the statistical significance of the treatment differences was determined using the one-way analysis of variance (ANOVA) followed by the Fisher least significant difference (LSD) test at p ≤ 0.05. The influence of waterlogging stress on morphological growth was detrimental for both tolerant and susceptible genotypes, with more severe consequences observed in the latter. Although adventitious roots were observed in both sets of genotypes above flooding levels, the tolerant genotypes exhibited a more rapid and vigorous development of these roots after 48 h of stress exposure. Tolerant genotypes displayed higher tolerance coefficients compared to susceptible genotypes. Furthermore, tolerant genotypes maintained elevated antioxidant potential, thereby minimizing oxidative stress. Conversely, susceptible genotypes exhibited higher accumulation of hydrogen peroxide (H₂O₂) and malondialdehyde content. Photosynthetic efficiency was reduced in all genotypes after 24 h of stress treatment, with a particularly drastic reduction in susceptible genotypes compared to their tolerant counterparts. Tolerant genotypes exhibited significantly higher activities of anaerobic metabolism enzymes, enabling prolonged survival under waterlogging conditions. Increase in proline content was observed in all the genotypes indicating the cellular osmotic balance adjustments in response to stress exposure. Consequently, the robust antioxidant potential and efficient anaerobic metabolism observed in the tolerant genotypes served as key mechanisms enabling their resilience to short-term waterlogging exposure. These findings underscore the promising potential of specific sesame genotypes in enhancing crop resilience against waterlogging stress, offering valuable insights for agricultural practices and breeding programs.

Deciduous woody plants like poplar (Populus spp.) have seasonal bud dormancy. It has been challenging to simultaneously delay the onset of bud dormancy in the fall and advance bud break in the spring, as bud dormancy, and bud break were thought to be controlled by different genetic factors. Here, we demonstrate that heterologous expression of the REVEILLE1 gene (named AaRVE1) from Agave (Agave americana) not only delays the onset of bud dormancy but also accelerates bud break in poplar in field trials. AaRVE1 heterologous expression increases poplar biomass yield by 166% in the greenhouse. Furthermore, we reveal that heterologous expression of AaRVE1 increases cytokinin contents, represses multiple dormancy-related genes, and up-regulates bud break-related genes, and that AaRVE1 functions as a transcriptional repressor and regulates the activity of the DORMANCY-ASSOCIATED PROTEIN 1 (DRM1) promoter. Our findings demonstrate that AaRVE1 appears to function as a regulator of bud dormancy and bud break, which has important implications for extending the growing season of deciduous trees in frost-free temperate and subtropical regions to increase crop yield.