Abstract

Four bread wheat genotypes with contrasting drought stress tolerance were studied. Expression levels of dehydrin (Wdhn13) and C-repeat binding factor (Cbf14, Cbf15) genes were investigated in leaves of two drought tolerant (Plainsman V, Mv Emese) and two sensitive (GK Élet, Cappelle Desprez) cultivars by semi-quantitative RT-PCR during drought treatment at anthesis. Coordinate induction of Cbf14, Cbf15 and Wdhn13 genes occurred at a late stage of stress treatment in all cultivars except the most sensitive Cappelle Desprez, where no induction was evident. The most pronounced late induction of genes was observed in the tolerant Mv Emese genotype. Cbf14, Cbf15 and Wdhn13 showed largely parallel changes of expression in stressed adult plants. The mRNA level of the same set of genes was measured in leaves of non-stressed seedlings with qRT-PCR method. Expression level of Wdhn13 was high and low in seedlings of tolerant and sensitive cultivars, respectively. Cbf15 specific transcript was barely detectable in leaves of non-stressed seedlings. In order to shed light on any potential difference in hormone responsiveness, seedlings were subjected to ABA treatment in vitro. At low hormone concentrations (10 and 20 µM ABA) consistently weaker ABA induced root growth retardation of GK Élet was found in comparison with the other three cultivars. Results highlight pronounced and late induction of a set of defence genes and low ABA sensitivity as features appearing in drought tolerant and sensitive responses, respectively. Data is discussed in the light of multifactorial determination of the complex phenotype of drought tolerance in wheat.

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