The effect of semidwarfing genes in wheat on plant height in diverse environment in Nebraska

Semidwarfing genes (most commonly Rht-B1b (Rht1), Rht-D1b (Rh2), and Rht8) and other semidwarf genes (Rht4, Rht5, Rht12, and Rht13) modify plant structure; reduce plant height; decrease lodging; and can increase harvest index, biomass, and grain yield in wheat (Triticum aestivum L.). In this study, sixty adapted wheat genotypes that were common to two advanced wheat breeding nurseries; Nebraska Interstate Nursery (NIN) and Nebraska Triplicate Nursery (NTN), were grown in 2004 and 2005 at six locations in Nebraska (Alliance, Clay Center, Lincoln, Mead, North Platte, and Sidney) using an randomized complete block design to measure their plant height and grain yield. The environment, genotypic effects and their interactions were significant (P\u3c0.05) for both traits. To determine if the semidwarf genotypes respond differently to the environment, the sixty genotypes were assayed using GA3 and molecular markers to establish the presence of Rht-B1b and, Rht-D1b (GA insensitive); Rht8, Rht4, Rht5, Rht12, and Rht13 (GA sensitive). The response to the environment was determined using stability analyses using linear regression (slope). The genotypic plant height means for semidwarf genotypes ranged from 72.5 to 89.3 cm and for nonsemidwarf genotypes from 78.6 to 94.4 cm. The correlation coefficients for plant height measurements in eastern Nebraska poorly predicted plant height in western Nebraska. The genotypic range of slope values for environmental stability for all the genotypes ranged from 0.76 to 1.33. Of the 60 genotypes, 49 were classified as the Rht-B1b which was the most common gene in our genotypes and it reduced plant height by 8.5% compared to the nonsemidwarf genotypes. There were 9 genotypes without Rht-B1b and Rht-D1b markers and they were GA-sensitive. We found no significant difference among Rht8 marker alleles, no reduction associated with the Rht5 marker, small but significant height reductions associated with the markers linked to Rht12, and Rht13 markers, and a small increase in plant height associated with the Rht4 marker indicating the markers were not diagnostic in this population