COMPARISON OF HYBRID AND INBRED HARD RED WINTER WHEAT (TRITICUM AESTIVUM L.) FOR RESPONSIVENESS AND YIELD STABILITY
Abstract
Estimates of yield responsiveness and stability were determined for hybrid and inbred hard red winter wheat (Triticum aestivum L.). Yield data were supplied by a commercial winter wheat breeding company, HybriTech Seed International, Inc. (Wichita, Kansas) for 147 hybrids and 261 inbreds. Hybrids included 30 single-cross (SC), 115 three-way (TW), and 2 commercial checks. Inbreds included 132 female parents (B-lines), 115 male parents (R-lines), and 14 commercial checks. Each entry was tested in at least two years and at five or more locations in total. Most entries were tested in a unique combination of site-years and thus each entry had its own unique data set. A linear regression was done on each entry, regressing its mean yield against the mean yield of the trial in which it was included. Yield responsiveness was estimated by comparing mean regression coefficients (b). Stability was estimated by comparing residual mean squares (s$\sp2$y.x). The mean yield of the hybrids, as a percent of the test means, was similar to the checks. Within the inbred group, the checks yielded about 11% more than the parental inbreds. Hybrids were significantly more responsive (b = 1.021) than inbreds (b = 0.991). Inbred lines exhibited a much wider range in responsiveness than did the hybrids. When tested for normality of distribution, the overall hybrid group as well as the inbred checks appeared normal, while the inbred parents did not fit a normal distribution. Hybrids were also more stable (s$\sp2$y.x = 35.3) than the hybrids (s$\sp2$y.x = 78.5). Within the hybrid group, the SC hybrids were more responsive (b = 1.056) than the TW hybrids (b = 1.013). Conversely, the TW were more stable (s$\sp2$y.x = 31.5) than the SC (s$\sp2$y.x = 39.9). There were no significant differences between the B- and R-lines for responsiveness. The R-lines, however, were more stable (s$\sp2$y.x = 65.9) than the B-lines (s$\sp2$y.x = 81.4). There were significant differences within each group for both responsiveness and stability. Parent-offspring regressions indicated that there was little relationship for responsiveness or stability.
Degree
Ph.D.
Subject Area
Agronomy
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