Agronomic parameters and drought tolerance indices of bread wheat genotypes as influenced by well-watered and water deficit conditions.

Abstract

Background: A primary threat to food security stems from the expanding global population and climate change, which have increased the frequency of droughts. Owing to shifting climatic conditions, abiotic stresses such as severe drought are intensifying, reducing wheat productivity. This study aimed to evaluate the response of elite drought-tolerant wheat genotypes to water deficit stress by analysing agronomic and physio-biochemical traits, with the goal of identifying promising genotypes for breeding.

Methods: Twenty wheat genotypes sourced from various national and international drought-tolerant nurseries, including a benchmark variety, were tested under water deficit and well-watered conditions over two consecutive years. The data collected included agronomic traits such as plant height (PH), days to heading (DH), days to anthesis (DA), days to physiological maturity (DPM), canopy temperature, SPAD values at different growth stages, intercepted photosynthetically active radiation above the canopy (IPARAC) and on the ground (IPAR OG), yield stability index (YSI), stress tolerance index (STI), stress index (SI), leaf area index (LAI), spike length (SL), grains per spike (GPS), 1000-grain weight (TSW), grain yield (GY; t/ha), and biomass yield (BY; t/ha).

Results: To streamline the study, two years of aggregated data were analysed for each parameter. Drought tolerance was assessed based on grain yield, and multitrait genotype‒ideotype distance (MGIDI) indices were employed to select drought-tolerant wheat genotypes. Significant differences were observed among the wheat genotypes across all measured parameters under both conditions. Under normal conditions, correlation analysis revealed that grain yield (GY) and biomass yield (BY) had the strongest positive relationship (r = 0.75**), followed by TSW, LAI, GPS, SL, PH, DPM, and DA. In contrast, under water deficit stress, BY exhibited a notable correlation with plant height (PH) (r = 0.42). Under both irrigated and water deficit stress situations, GY had positive and substantial correlations with PH, DA, DPM, GPS, SL, the STI, and the YSI. Two of the ten main components (PCs) accounted for 52.3% and 50.4% of the overall variation under water deficit and well-watered conditions, respectively. Additionally, the genotypes were separated into three clusters via a cluster heatmap, and the most tolerant genotypes (E38, E40, E41, E35, and E33) were found to be in cluster 3, which revealed their genetic relatedness. Genotypes E9 and E29 were found to be sensitive to water deficit, whereas genotypes E40, E38, and E35 were drought tolerant, according to tolerance indices.

Conclusion: Plant breeders may find the MGIDI useful for selecting genotypes on the basis of a variety of characteristics because it is a straightforward and robust selection method. Among the 20 wheat genotypes, the most stable and productive were E38, E30, E35, E40, and E34, according to an analysis of MGIDI for diverse settings. This was likely caused by the high MPS (mean performance and stability) of specific traits under different situations. The features that have been identified can be used as genitors in hybridization procedures to create wheat breeding materials that are resistant to drought. The genotypes and features that were found to be drought tolerant could be used to create new genotypes that are resistant to drought stress.