Heat and drought resistance criteria in spring bread wheat (Triticum aestivum L.): Morpho-physiological parameters for heat tolerance

This study was aimed at evaluating some morpho-physiological parameters such as stomatal conductance (gs), canopy temperature (CT), canopy temperature depression (CTD) and stay green duration (SGD) in terms of heat tolerance. For this purpose, trials designed according to randomized complete blocks were conducted with twenty-four spring bread wheat genotypes as three replicated in the Research and Application Area of Field Crops Department of Agricultural Faculty of Cukurova University in 2002 to 2003 and 2003 to 2004 growth seasons. The measurements of gs were made at two different dates at heading stage in 2003 to 2004 growth season. CT was measured at two growth stages (late milky and soft dough) in 2002 to 2003 (first) season and it was also measured at two different hours at the complete heading stage in 2003 to 2004 (second) season. CTD was measured at two different hours at the complete heading stage in the second season. The other morpho- physiological parameter was SGD, which was determined in the first growth season. As a result: (1) The high gs values were observed at both measuring dates even though there was no significant differences among the genotypes; (2) CT showed significant differences except T2 measurement in 2003 to 2004 season, yet significant negative correlations were found between CT and grain yield (GY) in 2003 to 2004 season and in general mean; (3) Despite not being significant differences among the genotypes, a strong positive correlation was found between CTD and GY; (4) In spite of the fact that genotypes did not show any statistical differences, it was found that SGD had a negative significant correlation with CT but positive non-significant correlation with GY. It is concluded from assessments of all physiological traits that such genotypes as Kauz/Altar 84//Ads, Varona Cno 79, Mon's'/Ald's'//Bow's' and WL6718 can be high yielding even if under heat stressed conditions, and can be used as gene pool in wheat breeding programs for tolerance to heat stress.