Drought resistance and wheat breeding

Abstract

The breeding of wheat ( Triticum species) for drought resistance has been indirect for the most part. The most direct approach has been identifying an appropriate crop maturity that maximizes growth and the accompanying yield component development. Beyond that, the improvement of response to drought has been rare. This is due, in great part, to the complexity of the problem and the lack of techniques and facilities that can be used to screen thousands of genotypes in practical plant breeding programs. Yield improvement is the prime goal in most wheat breeding programs. Unfortunately, many of the favourable plant responses to moisture stress leave negative effects on grain yield. An impressive number of research reports in the 1970's relating to the various aspects of drought resistance in wheat bodes well for directed selection for improved genotypic performance under moisture-stress conditions. Cooperative research between plant breeders and plant physiologist is the key to accomplishing this goal. This should begin with careful choices of parental and germplasm materials. Regional cultivar-yield-testing was initiated by the U.S. Department of Agriculture and cooperating state experiment stations in the early 1930's. This program has been eminently successful in identifying cultivars that had the desired adaptation characteristics. This guideline for a successful testing program for advanced lines needs to be introduced early in the breeding program. Therefore, breeding procedures should include as much early generation multilocational testing and selection as feasible. This may include early generation bulks, F 2- or F 3-derived lines, and F 2 selection composites. High average-yield and stability of performance are still the best criteria for selection. The earlier in the breeding program that adaptive (high average) yield can be identified the better. Variability of selected phenotypes, within limits, may provide populational buffering in moisture-stress situations that are variable in their location, intensity, duration and seasonal appearance.