Effect of replications and environment on wheat plant height

The number of replications required to accurately determine plant height and to detect the desired difference between wheat genotypes in diverse environments were determined using statistical formulas and data from a total of eight advanced breeding trails in three distinct ecogeographic zones. Despite the ecogeographic site diversity, measuring plant height on only two replications provided an accurate estimate of the mean for each trial and of detectable differences between wheat genotypes. The second part of study emphasized the effect of environment on wheat plant height. Tall wheats (Triticum aestivum L.) are preferred in drought prone western Nebraska. However, semidwarf wheats are desirable for eastern Nebraska where water is less of a limitation. Selecting tall wheats for western Nebraska is difficult in eastern Nebraska where the 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 over Nebraska environments representing three ecogeographic zones was performed using plant height data on released cultivars and advanced experimental genotypes. Genotypes were significantly different and the genotype by environment interaction was significant for plant height. Similar results were obtained when the genotypes were classified and analyzed separately as semidwarf (gibberellic acid (GA)-insensitive) or conventional height (GA-sensitive) wheats. The genotype by environment interaction was partitioned and mean squares associated with the environment x (semidwarf vs conventional height wheat), environment x semidwarf wheat, and environment x conventional height wheat were all found significant. Using regression estimates of stability, semidwarf genotypes were more stable (lower b values) than conventional height genotypes. Though GA-sensitive (conventional height) genotypes were on average taller than insensitive (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. Conventional height wheats with similar environmental responses were not identified. The stability of yield was independent from the stability of plant height