Morpho-physiological and biochemical stability of two-rowed malt barley ( Hordeum vulgare ) in the sub tropics with harsh recurring heat stress environments

Identification of malt barley (Hordeum vulgare L.) genotypes capable of withstanding reoccurring heat stress occurrences during the growing season is important to sustain the production, yield, and quality of this crop. This study evaluated the morpho-physiological and biochemical performance of 16 two-rowed malt barley genotypes across two consecutive cropping seasons (2020–2021 and 2021–2022) in Karnal, India. The genotypes, comprising eight released varieties and eight advanced breeding lines, were assessed using a randomized block design with three replications. Data were analyzed separately for each year because of differences in results caused by higher-than-normal temperatures during the reproductive and grain-filling period in 2021–2022 compared to 2020–2021. Grain yield, thousand-grain weight, and test weight were substantially reduced in 2021–2022, while traits like days to maturity, plant height, and grain filling duration were higher under normal conditions (2020–2021). Thousand-grain weight was strongly correlated with grain yield and grain boldness under heat stress. Protein content was positively associated with tiller number and moisture content but negatively with starch content. During 2021–2022, genotypes DWRB-229 and DWRB-160 exhibited resilience by maintaining extended growth periods and delayed maturity under heat stress. Genotypes DWRB-160 and RD-2849 were taller, had superior plant vigor, and produced stable yield. Genotypes DWRB-91 and DWRB-234 had yield losses of 1.03 and 13.15%, respectively but maintained plant height. Therefore, this study identified promising malt barley genotypes for breeding programs aimed at developing heat-resilient barley varieties for regions prone to heat stress during the growing season.