Magnitude and Consistency of Heterosis in Crosses among Plains-type Cotton Cultivars

This study was conducted to determine the magnitude and consistency of midparent (MP) and high parent (HP) heterosis over locations and/or years on cotton (Gossypium hirsutum L.) lint yield, lint percents, and fiber properties. The parents, F1s, and F2s for all possible crosses among five Plains-type cultivars, ignoring reciprocals, were evaluated in replicated experiments conducted at three irrigated locations in Oklahoma for 3 years. Additional analyses were performed to determine general (GCA) vs. specific combining ability (SCA) effects of heterosis and the consistency of heterosis over locations, years, or both. MP heterosis in the F1 and F2 was detected for all traits except uniformity index in the F1 ; HP heterosis in the F1 was reported for all traits. MP heterosis for lint yield was relatively large with increases up to 173 kg/ha (34.0% heterosis) in the F1 and 102 kg/ha (18.6%) in the F2; and in the F1 , HP heterosis ranged up to 145 kg/ha (26.6%). Generally, heterosis was relatively small for the remaining traits in this study. Based on overall mean heterosis, among the 10 crosses studied, three could be eliminated from consideration, four displayed one or more negative trends, and three were highly promising for hybrid production. In the F2 , GCA effects for heterosis were found for all traits except 50% span length (SL) and micronaire while SCA effects for heterosis were found for all traits except lint yield, 50% SL, and 1/8-inch gauge stelometer (T1 ). Environmental interactions with GCA and SCA were observed for all traits except 50% SL and T1 . Significant inconsistencies over environments occurred for MP and/or HP heterosis for all traits except uniformity index and T1Agronom