Abstract
The response of modern winter wheat varieties to soil drought was studied with aim of phenotyping their drought tolerance characteristics and identification of the most informative indices that may be suitable for use in breeding programs. Plants of winter bread wheat (Triticum aestivum L.) varieties Podolyanka, Khurtovyna, Vinnychanka and Prydniprovska were grown in a pot experiment. The soil moisture for control plants was maintained at a level of 70% of field capacity (FC) throughout the vegetative stage. At the flowering, watering of the treated plants was stopped to reduce the soil moisture to a level of 30% FC and then this soil moisture level was maintained for 10 days. After that, the irrigation of the treated plants was restored to the level of control. It was found that in the flag leaf under drought condition, the chlorophyll content, net CO2 assimilation rate, and transpiration rate decreased, while the leaf water deficit, the ratio of photorespiration to CO2 assimilation, and the activity of chloroplasts antioxidant enzymes (superoxide dismutase and ascorbate peroxidase) increased. The ten-day drought significantly reduced the grain yield from the plant. Calculations of the relative changes in the physiological parameters of treated plants as compared to the control were the most informative for the differentiation of varieties for drought tolerance. Relative changes in the content of chlorophyll in the flag leaf under drought and reduction in the total biomass of the plant closely correlated with a decrease in grain productivity (r = 0.92 and r = 0.96 respectively). There was also a significant correlation of grain productivity with a decrease in the NAR measured in the period of drought (r = 0.68). Therefore, the maintenance of the photosynthetic function of plants under conditions of insufficient water supply plays a determinant role in reducing the grain productivity losses. The relative changes in the chlorophyll content and CO2 assimilation rate in plants subjected to drought as compared to control may be used as markers of drought tolerance of genotypes for genetic improvement of wheat by conventional breeding and biotechnological methods.
Highlights
Abiotic and biotic stress factors cause significant losses of crop yield
Decrease of soil moisture to 30% of the field capacity (FC) four days after the cessation of watering increased the level of water deficit in the flag leaf by 57.8–69.9% for the Podolyanka, Khurtovyna, Vinnychanka, and by 141.2% for Prydniprovska variety (Fig. 1)
During a prolonged drought (7 days at 30% FC), the water deficit increased in the flag leaf of the Vinnychanka, Prydniprovska and Khurtovyna varieties
Summary
Abiotic and biotic stress factors cause significant losses of crop yield. It is necessary to know which physiological mechanisms are important for maintaining the production process under water stress conditions in order to improve them through genetic and selection methods. Work in this direction is complicated by the fact that drought tolerance is a complex trait that characterizes the ability of the plant organism to retain its basic functions in the conditions of a lack of moisture, and in the first place, to maximize the realization of genetic potential of yield (Passioura, 2012). In recent years, the study of the possibilities of breeding based on physiological characteristics that determine or closely correlate with productivity in conditions of drought, arouse considerable interest (Lopes et al, 2014)
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