PLANT HEIGHT RESPONSE OF SEMIDWARF AND NONSEMIDWARF WHEATS TO THE ENVIRONMENT

Nonsemidwarf wheats (Triticum aestivum L.) are preferred in drought-pr one dryland agriculture but are difficult to select under higher rainf all environments where early generation breeding nurseries are often l ocated. To determine the importance of genotype differences in height and the genotype x environment interaction, a combined analysis of var iance across three ecogeographic zones was performed using genotype pl ant 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 e nvironment interaction was also partitioned, and the environment x (se midwarf vs. nonsemidwarf wheat), environment x semidwarf wheat, and en vironment x nonsemidwarf wheat were all significant. The importance of significant genotype x environment interactions is (i) plant height i n the eastern Nebraska poorly predicted plant height in western Nebras ka, (ii) nonsemidwarf wheats interacted differently than semidwarf whe ats with the environment, (iii) plant height should be measured in eac h ecogeographic zone or al least the eastern zone and either the centr al or northwestern zone, and (iv) among nonsemidwarf and semidwarf whe ats a variety of responses to the environment were found. With regress ion estimates of stability, semidwarf genotypes were more stable (lowe r 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. Nonse midwarf wheats with similar environmental responses were not identifie d.