Author : Hsu Mayt Noe Hnin

Summary : The multiseason phenotyping of the Heat-MAGIC population under field and controlled stress conditions revealed the wide phenotypic variation and consistent positive correlations of grain yield (GYLD) with plant height (HT), panicle length (PL), thousand grain weight (TGW), and spikelet fertility (SF), highlighting the necessity of using these traits as indirect selection criteria rather than selecting for yield alone. The significant negative correlations of GYLD with Zn and days to 50% flowering (DTF) suggested trade­offs and potential heat escape mechanisms. Environmental regression identified genotype x seasonal interactions, whereas stability analysis and stress tolerance indices helped pinpoint stable genotypes. The quantitative trait locus (QTL) for heat tolerance, qGYLD7 (explaining 25.9% of the phenotypic variance), was identified under the controlled stress condition, and multitrait QTL associated with PL, HT, and DTF colocalized on chromosome 3 at single and combined sites under normal and stress conditions. Candidate genes, such as OsVQ29, OsNAC15, and OsCCX3, were linked to yield and nutritional traits and offered molecular breeding targets. The genotypes with stable high yield and Zn, such as G66 and G53, need further breeding and multienvironment testing for validation. This research offers valuable genetic insights and tools for breeding climate-resilient, high- yielding, and nutritious rice varieties.