GENETIC-CONTROL OF ACQUIRED HIGH-TEMPERATURE TOLERANCE IN WINTER-WHEAT

The development of high temperature-tolerant wheat (Triticum aestivum L.) germplasm is necessary to improve plant productivity under high-temperature stress environments. The quantification of high temperature tolerance and the characterization of its genetic control are necessary for germplasm enhancement efforts. This study was conducted to determine the genetic control of acquired high temperature tolerance in common bread wheat cultivars. Reduction of 2,3,5-triphenyltetrazolium chloride (TTC) by heat-stressed seedling leaves was used as a quantitative measure to characterize acquired high temperature tolerance. Eleven-day-old seedlings of 20 F-1 progeny produced through a complete 5 x 5 ('Payne', 'Siouxland', 'Sturdy','TAM W-101', and 'TAM 108') diallel mating design were acclimated at 37 degrees C for 24 hours, followed by a 2-hour incubation at 50 degrees C. Under these test conditions, acquired high temperature tolerance ranged from a high of 75.7% for the genotype TAM W-101 x TAM 108, to a low of 37.3% for the genotype Payne x Siouxland. Partitioning of genotypic variance revealed that only the general combining ability component effect was statistically highly significant, accounting for 67% of the total genotypic variation, These results suggest that enhancing the level of high temperature tolerance in wheat germplasm is feasible utilizing existing levels of genetic variability and exploiting additive genetic effects associated with high temperature tolerance.