Physiological characterization of Turkish bread wheat genotypes for resistance to late drought stress


Abstract: A number of physiological traits have been proposed as selection criteria for late drought resistance and grain yield improvement in wheat. To characterize them in terms of late drought resistance, 64 bread wheat genotypes were evaluated for canopy temperature difference (CTD), leaf senescence rate (LSR), SPAD chlorophyll value, initial fluorescence (Fo), maximum fluorescence (Fm), variable fluorescence (Fv), maximum quantum efficiency of PSII (Fv/Fm), leaf ash content, and grain ash content in two field experiments conducted in irrigated and late drought conditions during the 2011-12 and 2012-13 seasons in Erzurum, Turkey. The experiments were conducted in an 8 x 8 lattice design with two replicates. Significant variation was observed among the genotypes for all the traits. Late drought decreased the grain yield, CTD, SPAD, Fm, Fv, Fv/Fm, and leaf ash content but increased LSR and grain ash content. The drought sensitivity of the genotypes was determined by a ranking method based on 25 traits measured in the late drought conditions. According to the rank-sum (RS) values of the genotypes, four genotypes were defined as resistant, 15 genotypes as medium resistant, 34 genotypes as medium sensitive, and 11 genotypes as sensitive. Resistant genotypes M?fitbey and Dağdaş 94 produced the highest grain yields in late drought conditions and appeared to be promising parents for the breeding of resistant cultivars. RS was negatively correlated with CTD, SPAD, Fm, Fv, and Fv/Fm, while it was positively correlated with LSR. For screening late drought-resistant genotypes, 15 days post anthesis (15DPA) is the optimum time for Fv, CTD, and SPAD measurements. The stepwise multiple linear regression analysis indicated that the Fv15DPA, Fv25DPA, CTD15DPA, and SPAD15DPA could explain 75.2% of the total variation in RS. Therefore, the Fv15DPA, Fv25DPA, CTD15DPA, and SPAD15DPA traits can be used as selection criteria as a combination for the classifying of wheat genotypes in terms of late drought resistance.

Keywords: Ash content, canopy temperature, chlorophyll, chlorophyll fluorescence, leaf senescence, ranking method

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