Genetic mapping of foliar and tassel heat stress tolerance in maize

Abstract

The frequency of heat stress events is expected to increase, further complicating the challenge of feeding a growing population. A better understanding of the genetic and molecular mechanisms of heat stress tolerance in maize (Zea mays L.) would facilitate the development of heat-tolerant cultivars. To address this knowledge gap, we evaluated two biparental recombinant inbred line (RIL) populations (B73 × NC350 and B73 × CML103) for leaf and tassel heat tolerance traits. Two foliar traits, leaf firing and leaf blotching, were evaluated at three vegetative growth stages. In B73 × NC350, two tassel traits, tassel blasting and reduction in spikelet size, were scored at flowering. We detected 22 quantitative trait loci (QTL), 15 in B73 × NC350 and seven in B73 × CML103. We previously observed that the development of leaf firing was differentiable between parents, and indeed, the different manifestations of the leaf firing trait were not significantly correlated and QTL did not co-localize. Leaf firing and leaf blotching traits were correlated at some vegetative growth stages, and most QTL did not co-localize. Quantitative trait loci number and position for traits measured at multiple vegetative stages were generally consistent. There was a single QTL for tassel blasting on chromosome 5. Heat-induced plant death segregated in B73 × CML103 and a major QTL was detected on chromosome 3, explaining 26.2% of phenotypic variance. Our study indicates that complex genetic mechanisms underlie the heat stress response in maize.