PLANT HEIGHT RESPONSE OF SEMIDWARF AND NONSEMIDWARF WHEATS TO THE ENVIRONMENT

Nonsemidwarf wheats (Triticum aestivum L.) are preferred in drought-prone dryland agriculture but are difficult to select under higher rainfall environments where early generation breeding nurseries are often located. To determine the importance of genotype differences in height and the genotype x environment interaction, a combined analysis of variance across three ecogeographic zones was performed using genotype plant height. Genotypes were significantly different and the genotype x environment interaction was significant. Similar results were obtained when the genotypes were classified as semidwarf [gibberellic acid (GA)-insensitive] or nonsemidwarf (GA-sensitive) wheats. The genotype x environment interaction was also partitioned, and the environment x (semidwarf vs. nonsemidwarf wheat), environment x semidwarf wheat, and environment x nonsemidwarf wheat were all significant. The importance of significant genotype x environment interactions is (i) plant height in the eastern Nebraska poorly predicted plant height in western Nebraska, (ii) nonsemidwarf wheats interacted differently than semidwarf wheats with the environment, (iii) plant height should be measured in each ecogeographic zone or al least the eastern zone and either the central or northwestern zone, and (iv) among nonsemidwarf and semidwarf wheats a variety of responses to the environment were found. With regression estimates of stability, semidwarf genotypes were more stable (lower b values) than nonsemidwarf genotypes. Though nonsemidwarf genotypes were on average taller than semidwarf genotypes, semidwarf genotypes with excellent stability could be identified that were not too tall in eastern Nebraska and retained their height in western Nebraska. Nonsemidwarf wheats with similar environmental responses were not identified.