Response of Wild Tetraploid Wheat (Triticum turgidum L.) to Heat Stress.

Elucidating mechanisms of heat tolerance and identifying reliable screening essays and germlasm sources for heat tolerance are essential for developing wheat varieties suited for the hotter areas of the world. Our objective was to determine heat tolerance of wild tetraploid wheat (Triticum turgidum L.). We screened sixteen wild tetraploid wheat accessions and two common wheat (Triticum aestivum L.) checks for their response to heat stress by measuring damage to the thylakoid membranes, flag leaves temperature depression (FLTD), and spikes temperature depression (STD) through exposure to heat stress for 16 days post-antheis.  Measurements were taken on anthesis date then 4, 8, 12, 16 d post-antheis under controlled optimum and heat-stressed conditions.  Individual kernel weight (IKW) and the heat susceptibility index (HSI) were also obtained. Prolonged exposure to heat stress was associated with an increased damage to thylakoid membranes as indicated by the high ratio of constant fluorescence (O) to peak variable fluorescence (P). Our results showed that HSIs of some wild tetraploid wheat accessions were better than the common heat-tolerant wheat cultivar ‘Kauz’. A positive and significant correlation was found between O/P ratio and each of FLTD and STD under heat-stressed conditions. A negative and significant correlation was found between each of FLTD and STD with HSI, based on the second and third measurements (4 and 8 d post-anthesis). Correlations obtained post the third measurement were not significant due to heat-induced, accelerated maturity and, thereof, lack of green leaf tissues. This study identified potential heat-tolerant, wild tetraploid wheat germplsm that can be incorporated into wheat breeding programs targeting the improvement of heat tolerance in cultivated common and durum wheat.