Maize and heat stress: Physiological, genetic, and molecular insights.

Global mean temperature is increasing at a rapid pace due to the rapid emission of greenhouse gases majorly from anthropogenic practices and predicted to rise up to 1.5°C above the pre-industrial level by the year 2050. The warming climate is affecting global crop production by altering biochemical, physiological, and metabolic processes resulting in poor growth, development, and reduced yield. Maize is susceptible to heat stress, particularly at the reproductive and early grain filling stages. Interestingly, heat stress impact on crops is closely regulated by associated environmental covariables such as humidity, vapor pressure deficit, soil moisture content, and solar radiation. Therefore, heat stress tolerance is considered as a complex trait, which requires multiple levels of regulations in plants. Exploring genetic diversity from landraces and wild accessions of maize is a promising approach to identify novel donors, traits, quantitative trait loci (QTLs), and genes, which can be introgressed into the elite cultivars. Indeed, genome wide association studies (GWAS) for mining of potential QTL(s) and dominant gene(s) is a major route of crop improvement. Conversely, mutation breeding is being utilized for generating variation in existing populations with narrow genetic background. Besides breeding approaches, augmented production of heat shock factors (HSFs) and heat shock proteins (HSPs) have been reported in transgenic maize to provide heat stress tolerance. Recent advancements in molecular techniques including clustered regularly interspaced short palindromic repeats (CRISPR) would expedite the process for developing thermotolerant maize genotypes.

Seed biopriming with potential bioagents influences physiological processes and plant defense enzymes to ameliorate sheath blight induced yield loss in rice (Oryza sativa L.).

Disease management with the use of conventional pesticides has emerged as a major threat to the environment and human health. Moreover, the increasing cost of pesticides and their use in staple crops such as rice is not economically sustainable. The present study utilized a combination of two commercial powder formulations of biocontrol agents, Trichoderma harzianum (Th38) and Pseudomonas fluorescens (Pf28) to induce resistance against sheath blight disease via seed biopriming in basmati rice variety Vasumati and compared the performance with systemic fungicide carbendazim. Sheath blight infection significantly increased the levels of stress indicators such as proline (0.8 to 4.25 folds), hydrogen peroxide (0.89 to 1.61 folds), and lipid peroxidation (2.4 to 2.6 folds) in the infected tissues as compared to the healthy control. On the contrary, biopriming with biocontrol formulation (BCF) significantly reduced the level of stress markers, and substantially enhanced the levels of defense enzymes such as peroxidase (1.04 to 1.18 folds), phenylalanine ammonia lyase (1.02 to 1.17 folds), lipoxygenase (1.2 to 1.6 folds), and total phenolics (74% to 83%) as compared to the infected control. Besides, improved photosynthesis (48% to 59%) and nitrate reductase activity (21% to 42%) showed a positive effect on yield and biomass, which compensated disease induced losses in bio-primed plants. Conversely, the comparative analysis of the efficacy levels of BCF with carbendazim revealed BCF as a potential and eco-friendly alternative for reducing disease impact and maintaining higher yield in rice under sheath blight infection.

Morphological characterization and expression analysis of genes for antioxidants enzymes in gamma rays induced M3 mutants of sunflower (Helianthus annuus L.) cultivar TNAUSUF-7.

PURPOSE: Objectives of the present investigation were to investigate the performance of mutant lines (mutant generation 3 (M3) generation) of sunflower obtained through gamma irradiations for yield and yield attributing traits including oil content (%), oil quality in terms of antioxidant activity and to investigate the expression of genes encoding antioxidant enzymes in control and gamma irradiated M3 lines. MATERIALS AND METHODS: Mutant lines (M3 generation) of sunflower variety TNAUSUF-7 obtained from 100 and 130 Gray (Gy) doses of gamma irradiation were evaluated for several traits such as days to 50% flowering, days to maturity, head diameter, number of filled seeds and unfilled seeds per head, fertility %, oil content %, antioxidant activity of oil and expression of genes encoding antioxidant enzymes. All the data were analyzed using different statistical tools. RESULTS: Our results showed that the gamma irradiation dose of 100 and 130 Gy induced significant variations in yield and yield attributing traits especially for days to 50% flowering, days to maturity, fertility %, antioxidant property of sunflower seed oil and expression of genes encoding antioxidant enzymes. CONCLUSIONS: From our results, it can be concluded that the gamma irradiations were effective in creating variations in terms of several traits in sunflower. Many desirable traits like reduced days to 50% flowering and maturity, increased fertility %, increased antioxidant activity of oil were observed in M3 lines. These M3 lines have the potential to be utilized as an inbred line in sunflower hybrid development or it could be used as a source of desirable traits in sunflower breeding programs.