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Hybrid and pureline hard winter wheat yield and stability

Koemel, John E., Jr.
Guenzi, Arron C.
Carver, Brett F.
Payton, Mark E.
Morgan, George H.
Smith, Edward L.
Pureline wheat (Triticum aestivum L.) cultivars continue to dominate production fields in the southern Great Plains despite numerous attempts to introduce hybrids during the past 28 yr. The objective of this study was to analyze yield trends and yield stability in both hybrid and pureline entries in the Oklahoma Variety-Hybrid Performance Nursery (VHPN). Grain yield data from 1975 to 1995 from four locations were selected and analyzed by relative yield indices. Regression equations across time were calculated for both hybrids and pure- lines relative to the mean performance of long-term check cultivars. Both hybrids and purelines evidenced yield improvement, with the yield of hybrids, in general, increasing at a greater rate than that of purelines. Predicted values in the last year tested indicated a 10.9% advantage of hybrids over purelines. Stability parameters were com- pared by regressing hybrid and pureline yields on an environmental index based on location mean yields for checks. Regression coefficients for hybrids and purelines were not significantly different from one, nor from each other. Confidence intervals for hybrid and pureline performance generally overlapped throughout the observed yield ranges, indicating no divergence in predicted grain yield as environ- mental yield potential increased. No significant differences in stability between hybrids and purelines were found by comparing variances represented by the pooled deviations for each cultivar type. Hybrid wheat offers an opportunity for increased grain yield in the southern Great Plains of the USA, but without a stability advantage over pure- line cultivars.