THE INFLUENCE OF ALIEN CHROMOSOMES ON THE DROUGHT RESISTANCE OF 'CHINESE SPRING' WHEAT. A PHYSIOLOGICAL AND MORPHOLOGICAL STUDY OF WHEAT/RYE ADDITION AND SUBSTITUTION LINES

The influence of some alien chromosomes on the drought resistance of wheat was determined by a physiological and morphological study of wheat/rye addition and substitution lines. The wheat parent used was Triticum aestivum L. em Thell, cv 'Chinese Spring', and the rye parent used was Secale cereale L. cv 'Imperial.' Their amphidiploid hybrid, Tritosecale Wittmach 'Triticale', disomic addition lines for chromosomes 1 through 7 of rye and 3 substitution lines of rye chromosomes in wheat were also available for this investigation.; Under drought stress, the grain yield of Chinese Spring and its aneuploid lines appeared to respond to a combination of morphological and physiological factors. The fraction of fertile florets, the number of fertile tillers and seed size were the important morphological traits that varied with the differences in the grain yield of all the genotypes tested. Among Chinese Spring and its aneuploid lines, substitution line 2R(,L)-2A(,S)/2A had the highest number of fertile florets and fertile tillers, a high percentage of viable pollen, and the highest average yielding ability under drought conditions. It also had the lowest reduction of grain yield due to moisture stress conditions.(,); Among physiological factors used in this investigation, the harvest index (grain yield/total above ground weight) showed an inverse correlation with the grain yield reduction under drought. The level of the hormone abscisic acid in artificially water-stressed leaves showed a positive correlation with the grain yield reduction under drought. It is possible, therefore, that drought-resistant genotypes are the ones that have better partitioning of photosynthetic assimilate to the grain than into straw, and accumulate lower levels of abscisic acid in response to water stress. The level of ethylene evolved from the artificially water-stressed leaves of all the genotypes did not correlate with their grain yield reduction under drought. The grain yield could not be predicted by photosynthetic rate, stomatal conductance and water potential values in any of the tested genotypes under either water-stressed or non-stressed conditions.; Chinese Spring/Imperial substitution line 2R(,L)-2A(,S)/2A showed significantly improved drought resistance. Three aneuploid lines are vigorous in vegetative growth and greatly inferior in grain yield. They are substitution lines 2R/2B and 2R/2D and addition line 2R. . . . (Author's abstract exceeds stipulated maximum length. Discontinued here with permission of author.) UMI...