ASSESSMENT OF PHYSIOLOGICAL PARAMETERS USEFUL IN SCREENING FOR TOLERANCE TO SOIL DROUGHT IN WINTER WHEAT (TRITICUM AESTIVUM L.) GENOTYPES

Application of physiological methods in selection process may help considerably to improve wheat breeding efficiency. In vegetation pot experiments with a collection of winter bread wheat genotypes of different provenance the drought tolerance screening methods were applied. Evaluation of drought effect in selected genotypes by chlorophyll fluorescence was based on the performance index (PI), the most sensitive fluorescence parameter characterizing better the drought susceptibility of plants. The genotypes differed in sensitivity of stomatal closure, and hence in the CO2 assimilation rate. In drought conditions the delayed stomatal closure caused mainly by higher osmotic adjustment led to higher net assimilation rate and higher production of assimilates. Similarly, transpiration efficiency of non-stressed plants was also related to their better drought tolerance. We identified several parameters well-correlated with relative grain yield decrease in drought stress conditions. Results were statistically significant for phenology and stomatal conductance of non-stressed plants, but we identified as promising also measurements of transpiration efficiency, osmotic adjustment and fast fluorescence kinetics using performance index as the most sensitive parameter.