|Nguyen henry t,|
Submitted to: Journal of Euphytica
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/4/1995
Publication Date: N/A
Citation: Interpretive Summary: Although hard red winter wheat is a cool-season crop it is grown in areas of the world where high temperatures are a perennial constraint to high yields, especially during the grain filling period. One very important way to overcome the adverse effects of high temperature is to develop thermal-tolerant wheat cultivars. In order to develop thermal-tolerant wheat plants one must have: a technique to measure tolerance, genetic diversity for tolerance, and an understanding of the genetic control of thermal tolerance. We have developed a technique to measure tolerance (TTC) and have found high levels of genetic diversity for thermal tolerance within wheat. In this study we used the TTC technique to measure acquired thermal tolerance of five hard red winter wheat cultivars and the progeny produced by intermating these five cultivars. We found that acquired thermal tolerance levels were very high in some progeny and very low in others. By measuring the progeny we were able to identify which wheat parents would be most beneficial for use in germplasm enhancement programs. Based on results from this study we feel that increasing the level of thermal tolerance in winter wheat is possible using existing genetic diversity in wheat and applying breeding techniques which maximize gains from additive effects controlling thermal tolerance.
Technical Abstract: The development of thermal-tolerant wheat (Triticum aestivum L.) germplasm is necessary to improve plant productivity under high-temperature stress environments. The quantification of thermal 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 thermal 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 thermal tolerance. Eleven-day-old seedlings of 20 F1 progeny produced through a complete 5 x 5 ('Payne', 'Siouxland', 'Sturdy', 'TAM W-101', and 'TAM 108') diallel mating design were acclimated at 37 deg C for 24 hours, followed by a 2-hour incubation at 50 deg C. Under these test conditions, acquired thermal tolerance ranged from a high of 75.7% for the genotype TAM MW-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 thermal tolerance in wheat germplasm is feasible utilizing existing levels of genetic variability and exploiting additive genetic effects associated with thermal tolerance.