Genome-wide association study delineating genomic regions contributing to heat stress tolerance at vegetative stage in mung bean [Vigna radiata (L.) R. Wilczek]

Abstract

Intensifying climate change and increasing heat stress pose a growing challenge to global food crop production, including mung bean [Vigna radiata (L.) R. Wilczek]. Mung bean is a vital protein-rich pulse crop with essential vitamins and micronutrients. However, rising heat stress increasingly constrains its production worldwide. Despite extensive studies on physiological and biochemical responses, genomic resources for heat tolerance in mung bean remain limited. This study employed a genome-wide association study (GWAS) using 5,758 high-quality SNPs to identify genomic regions and candidate genes associated with heat stress tolerance at the vegetative stage. A globally diverse panel of 396 genotypes was evaluated under optimal (34/25 °C) and heat stress (42/30 °C) conditions, assessing six major morpho-physiological traits including leaf chlorophyll index measured by SPAD, photosystem II maximum quantum efficiency (Fv/Fm), membrane damage, plant height, days to flowering and plant biomass. Marker-trait association (MTA) analysis identified nine significant MTAs under optimal conditions and 12 under heat stress. Under heat stress, two MTAs for days to flowering were detected on chromosome (Chr) 3 (S3_8626095) and Chr5 (S5_26149549). These SNPs explained 2.3% to 4.3% of the phenotypic variance explained (PVE). Eleven putative candidate genes were identified, including LOC106757788 encoding phytochrome A-like proteins, LOC106770897 encoding leucine-rich repeat extension-like proteins (maintaining structural integrity under heat stress), and LOC106761867 encoding calcium ATPases (maintaining low cytoplasmic calcium and preventing cytotoxicity). These findings identify key genomic regions and pathways associated with heat stress tolerance, offering valuable resources for marker-assisted breeding of heat-resilient mung bean cultivars. Further validation of candidate genes will enable designing of improved climate resilient varieties. This article supports United Nations’ Sustainable Development Goal: SDG-2 (Zero Hunger) by advancing molecular and cytogenetic research for the genetic improvement of mung bean.