Drought is one of the major environmental factors reducing grain production of rainfed wheat in semi-arid regions. The morphological and physiological basis of drought resistance in wheat (Triticum aestivum L.) cv. 'Chinese Spring', rye (Secale cereale L.) cv. 'Imperial', barley (Hordeum vulgare L.) cv. 'Betzes', and accession G870 (Dasypyrum villosum) and their derived disomic addition lines, developed by Dr. E. R. Sears or Dr. A. K. M. R. Islam, were studied in the field and glasshouse under nonstressed and stressed conditions. The four parental genotypes were first compared with each other for their performance in the field. Results from waterstressed conditions showed that Imperial rye was superior for plant height, above ground biomass, grain yield, and its components such as number of spikelets, and florets per main spike. Chinese Spring wheat and Betzes barley were intermediate in performance for most of the plant characters studied. Dasypyrum villosum G870 was the poor entry for the characters studied.

The glasshouse, gravimetric-pot studies of root dry matter, total biomass, the amount of water used and water-use efficiency also confirmed the field results. Imperial rye was assumed to be the most drought resistant because it produced larger root dry matter and total biomass while it consumed a smaller amount of water. Dasypyrum villosum was assumed to be drought sensitive because it showed lower means for water-use efficiency, root dry matter, and consumed a larger amount of water. Chinese Spring wheat and Betzes barley were intermediate.

The disomic addition lines were primarily used to study the effect of alien chromosomes of Imperial rye, Betzes barley, and Dasypyrum villosum G870 on the recipient genome of Chinese Spring wheat and to identify alien chromosome(s) carrying gene(s) which are responsible for the improved adaptation to water-stressed conditions. Among Chinese Spring wheat and the disomic addition lines, those for Imperial rye chromosome 2 and Betzes barley chromosome 4 had better performance over the other genotypes for above ground biomass, number of tillers, number of spikes, dry matter, amount of water consumed, and water-use efficiency. These alien chromosomes may carry loci which are responsible for the expression of plant characters that confer drought resistance. Grain yield data suggested that rye chromosome 2 also carries undesirable gene(s) which cause partial floret sterility. However, these gene(s) are not present on Betzes barley chromosome 4, because the disomic addition line for 4H had significantly higher grain yield than other disomic addition lines.

References:

Shakir, H. S. 1992. Drought resistance in wheat relatives and their addition lines. Ph.D. Dissertation. University of California, Riverside, CA 92521, USA.