Triple Testcross Analysis to Detect Epistasis in Maize
1997
Wolf, Duane P. | Hallauer, R.
Maize (Zea mays L.) breeders have successfully exploited heterosis by crossing inbred lines to develop hybrids. Epistatic effects can contribute to the expression of heterosis for specific hybrids. The hybrid B73 × Mo17 was a widely grown hybrid with exceptional performance in the central U.S. Corn Belt during the late 1970s and early 1980s. The objective of this study was to determine if epistatic effects contribute significantly to the performance of B73 × Mo17. With use of the triple testcross design, 100 random F₂ plants from B73 × Mo17 were testcrossed to B73, Mo17, and their F₁. The 300 testcrosses were evaluated at three locations in 1992 and two locations in 1993. Triple testcross analysis suggested that epistatic effects were important for ear length, number of kernel rows, ear height, and flowering traits. In the analysis of variance, additive by additive effects were not significant for grain yield, whereas additive by dominance and dominance by dominance effects were significant. The additive by additive by environment interaction was more important than additive by additive effects per se for grain yield. Epistatic deviations from the comparison of testcross means suggest that B73 had favorable additive by additive effects for grain yield, barren plants, kernel-row number, ear height, and silk delay. Inbred Mo17 had favorable additive by additive effects for ear length. The presence of significant positive epistatic effects may have contributed to the expression of heterosis and could explain why B73 × Mo17 was an exceptional and widely grown hybrid. Journal Paper no. J-16790 of the Iowa Agric. and Home Econ. Exp. Stn., Ames, IA 50011. Project 3082. Part of a thesis submitted by D.P. Wolf in partial fulfillment of the requirements for the Ph.D. degree.
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