Agronomic Comparisons among Wheat Lines Nearly Isogenic for Three Reduced‐Height Genes1

Abstract

The two most commonly used reduced‐height genes of wheat (Triticum aestivum L.) are Rht1, and Rht2. The Rht3, gene is known to be a potent height‐reducing gene. Information is limited as to the comparative effects of these three genes on agronomic traits, especially when placed in a common genetic background. This study made multiple site‐year comparisons in Washington for grain yield, plant height, volume weight, kernel weight, and tiller number among five reduced‐height, near‐isogenic lines and their recurrent parent, ‘Burt’. One line had the Rht3, gene. One line each had the Rht1, and Rht2, genes combined from ‘Norin 10’ and from ‘Suwon 92’. One line each had either the Rht1 or Rht2, gene separately from these two sources. Plant heights of lines with either Rht1, or Rht2, alone, Rht1, and Rht2, combined, and with Rht3, were reduced 24, 52, and 64%, respectively. The Rht3, line had the lowest (P<0.05) across‐test mean yield of 3360 kg ha−1. The two lines with both Rht1, and Rht2, exceeded (P<0.05) the yield of the Rht3, line with means of 3660 and 3840 kg ha−1; these values were less (P<0.05) than the Burt mean yield of 4440 kg ha−1 as well as the yields (4300 and 4900 kg ha−1) of lines with either Rht1 or Rht2. The Suwon 92 derived line with either Rht1 or Rht2, exceeded (P<0.05) the mean yields of other lines and Burt by 10 to 46%. The Rht3 line had significantly lower (P<0.05) mean volume weight, kernel weight, and tiller number than the other lines and Burt. Reductions in these traits of the Rht3 line compared to Burt were 11, 31, and 11% respectively. Lines with one or both Rht1 and Rht2, genes had lower (P<0.05) kernel weights than Burt. All Rht genes reduced volume weight. Although Rht3, is an effective height‐reducing gene, it caused negative effects on yield, volume weight, kernel weight, and tiller number. Single dosages of Rht1, or Rht2, caused neutral or positive effects on yield and tiller number, and warrant use in breeding.