Identification of a major locus controlling high-temperature tolerance in maize tassels

Abstract

High-temperature stress severely affects maize production and leads to significant yield losses. Breeding maize varieties with enhanced high-temperature tolerance is an effective strategy to mitigate these adverse effects. Identifying quantitative trait loci (QTLs) and candidate genes associated with heat tolerance is therefore of great importance for maize improvement. In this study, a high-temperature-tolerant inbred line PHBA6 and a high-temperature-susceptible line J63 were crossed to develop an F₂ population for initial QTL mapping. Tassel desiccation was used as the phenotypic indicator of heat tolerance. Initial QTL mapping conducted in 2015 and 2016 consistently identified two QTLs: a major QTL, qMd3, on chromosome 3 and a minor QTL, qMd9, on chromosome 9, explaining 10.72% and 5.74% of the phenotypic variance, respectively. Subsequent fine mapping of qMd3 was carried out using advanced-generation recombinant progenies derived from the F₂ population, which progressively narrowed the candidate interval from 59 Mb to 1.2 Mb between the markers KASP029 and KASP032. This study identified and refined a major QTL associated with high-temperature tolerance in maize, providing a solid foundation for the subsequent identification and functional characterization of candidate genes, as well as for marker-assisted breeding of heat-tolerant maize varieties.