Analysis of combining ability for stem-related traits and its correlations with lodging resistance heterosis in hybrid wheat

With the application of hybrid wheat, lodging is becoming one of the major factors limiting high yield in its production. However, few studies have focused on combining ability and heterosis analysis of stem-related traits. In this study, 24 crosses were made according to NCII genetic design, using the three (photo-sensitive male sterile lines)×eight (restorer lines) incomplete diallel crosses. The length of basal second internode (LBSI) and breaking strength of basal second internode (BSBSI) as well as other stem-related traits were used to perform the principal component analysis (PCA), combining ability and heterosis analysis. The PCA results showed that the variables could be classified into two main factors, which were named as the positive factor (factor 1) and the negative factor (factor 2), and accounted for 52.3 and 33.2%, respectively, of the total variance in different variables, combined with the analysis for index weight indicated that the factor 1-related traits play positive roles in lodging resistance formation of hybrids. Combining ability variance analysis indicated that its genetic performance was mainly dominated by additive gene effects, and the hybrid combinations with higher lodging resistance can be selected by using of 14GF6085 (R1), 14GF6343-2 (R4), 14GF6937 (R6), 14GF7433-1 (R7), and BS1086 (M3), which are with the features with lower general combining ability (GCA) effects of factor 2-related traits whereas higher GCA effects of factor 1-related traits. The heterosis analysis showed that the wide range of heterosis varied with the traits and combinations, and GCA or specific combining ability (SCA) effects of factor 1-related traits except wall thickness of basal second internode (WTBSI) were positively and closely related to the heterosis of lodging resistance. Generally, the correlation coefficients of heterosis to GCA effects of sterile lines (GCAm) of factor 1-related traits are significantly higher than that to GCA of restorer lines (GCAr) and SCA, combined with the higher GCAm variance values of factor 1-related traits compared to GCAr, the GCAm of factor 1-related traits should be particularly considered when breeding hybrid combinations. The heritability analysis showed that the narrow-sense heritability of the diameter of basal second internode (DBSI) and the center of gravity height (TCGH) were obviously lower (<60%) than other traits, suggesting that these two traits were suitable for selection in higher generation for parental breeding. These could provide a theoretical basis for parental breeding and heterosis utilization of lodging resistance.