Productivity of a doubled haploid winter wheat population under heat stress

Breeding of new winter wheat cultivars with good heat tolerance requires better understanding of the genetic background of heat tolerance. In the present work the effect of heat stress on the 6^th day after heading was investigated in a doubled haploid (DH) population arising from a cross between heat-sensitive (Plainsman V) and heat-tolerant (Mv Magma) cultivars. Averaged over the population, heat stress was found to result in a significant reduction in biomass, grain yield and grain number per plant, and in thousand-kernel weight (TKW) and harvest index. High temperature had the greatest effect on the grain yield, with a drop of 36.2% compared with the control. This could be attributed jointly to significant reductions in the TKW of the main ear and in the grain number of the side tillers. The relationship between the yield parameters was confirmed by the positive correlations obtained for the lines in the population. The diverse levels of heat tolerance in the different lines were confirmed by the significant differences in the reduction in the chlorophyll content (SPAD index) of the flag-leaves and in yield parameters. The changes in yield components in stress condition, however, can be still the most effective tools for heat stress evaluation.