Impact of Reciprocal Crosses On Grain Yield, Combining Ability Estimation and Heterotic Group Classification in Diallel.

Whether the reciprocal crosses should be included in a diallel? How the inclusion of reciprcoal lines in a diallel will impact genetic effects and variances of general combining ability (GCA), specific combining ability (SCA) and maize heterotic classification? The answers to these questions are not available yet. 

This study employed a 12-parental diallel with Griffing Method 3 and method 4 three environments. The objectives of this study were to identify  1) if reciprocal crosses will impact grain yield (GY) of crosses, GCA and SCA effect and variance estimation? If yes, what are the impacts? 2) if reciprocal effects (REC) offer useful information in maize heterotic group classification?  The results showed that inclusion of reciprocal crosses in a diallel had great impact on actual grain yield (GY), and on the estimations of GCA, and SCA effects; and if random model is assumed, the residual and GCA variances tend to decrease and the SCA variances tend to increase with number of parent line increasing. Since reciprocal cross inclusion impact GY and SCA,which, in turn,  has great impact on maize heterotic group classification. In addition, REC effects calculated from a diallel with reciprocal crosses will facilitate clarification  in maize heterotic group classification. Suitable maize hetrotic groups were discussed, and three heterotic groups seems an idea number in maize heterotic group classification for improving breeding efficient with REC effects were considered as well as GY and SCA effects.