Evaluation of Near‐Isogenic Lines for Three Height‐Reducing Genes in Hard Red Spring Wheat

ABSTRACT The most common genes for semidwarf habit in modern wheat ( Triticum aestivum L.) cultivars are found at the Rht‐B1 and Rht‐D1 loci on chromosomes 4B and 4D, respectively. An alternative gene for semidwarf habit, Rht8 , has shown potential as a replacement for Rht‐B1b and Rht‐D1b in some environments. The objective of the present study was to assess the impact of the height‐reducing gene Rht8 relative to Rht‐B1b and Rht‐D1b on performance of spring wheat in Montana and Washington environments characterized by terminal drought stress. Evaluation of near‐isogenic lines developed in four genetic backgrounds showed that Rht‐B1b , Rht‐D1b , and Rht8 caused height reduction of 19, 20, and 6.5%, respectively, relative to wild‐type near‐isogenic lines over 12 environments. An increase in grain yield was associated with reduced height for lines containing Rht‐B1b and Rht‐D1b based on means over the four genetic backgrounds and 10 environments. Height reduction and yield increase associated with Rht‐B1b and Rht‐D1b were significant in most environments. Lines with Rht8 yielded less than wild‐type based on means over environments and in 3 of 10 individual environments. Reduced height lines with Rht‐B1b and Rht‐D1b tended to have a higher harvest index and more seed per spike than wild‐type lines and reduced height lines with Rht8 . In sum, our results suggest that Rht‐B1b and Rht‐D1b are superior to Rht8 as a source for height reduction for spring wheat in the tested environments.