PLANT TRAITS RELATED TO YIELD OF WHEAT IN EARLY, LATE, OR CONTINUOUS DROUGHT CONDITIONS (REPRINTED FROM WHEAT - PROSPECTS FOR GLOBAL IMPROVEMENT, 1998)

Bread wheats (Triticum aestivum L.) were evaluated for plant character istics contributing to grain yield and adaptation under various drough t patterns. The usefulness of these traits as explicit selection crite ria in developing drought tolerant wheat varieties was investigated in three experiments. Cultivars from four germplasm groups, representing the four relevant major and distinct global wheat growing environment s, were grown under the respective simulated early, late, continuous a nd no drought conditions by manipulating irrigation in north western M exico. Additionally, 560 advanced lines from the CIMMYT breeding progr am were grown under late drought conditions, and 16 randomly selected advanced genotypes were studied in more detail under late and no droug ht conditions. In these three studies, the association between yield i n drought-stressed environments and yield in non drought-stressed envi ronments was interpreted to reflect genotypic high yield potential, ma inly by way of high biomass development. However, yield potential only partly explained the superior performance under drought. For each pat tern of drought stress, particular and often different plant traits we re identified that further contributed specific adaptation to the dist inct drought stress conditions. Knowledge of these traits will be usef ul for developing CIMMYT germplasm for specific drought-stressed areas . Ultimately, these studies demonstrate that both yield potential and specific adaptation traits are useful criteria in breeding for drought environments, and should be combined to achieve optimum performance a nd adaptation to drought stress.