Analysis of the combining ability of the main agronomic traits in brown midrib genotype sorghum sterile lines

A field experiment was conducted to analyze the heritability and combining ability of the 7 main agronomic traits from 57 hybridized combinations of brown midrib (BMR) sorghum sterile lines using NCⅡ incomplete diallel cross design. A total of 19 BMR Sorghum sterile lines and 3 BMR sudan grass lines with independent breeding were used as female and male parents, respectively. The results showed that four agronomic indexes (plant height, leaf number, middle leaf length, and middle leaf width) had mid parent heterosis. Plant height and middle leaf length showed high parent heterosis; leaf number, middle leaf length, and middle leaf width expressed competitive heterosis; whereas tiller number, stem diameter, and panicle length showed negative heterosis. There were no significant differences in the blocks among the main agronomic traits (P>0.05), yet there was a significant difference in the combination (P<0.01). The stem diameter and main panicle length were controlled by both additive and non-additive effects, whereas non-additive effects were very strong in plant height, leaf number, middle leaf length, and middle leaf width. The main stem length should be selected during the early stage, whereas the other traits should be selected during the later stages except for the middle leaf width that was affected by environmental conditions. Based on the comprehensive analysis, the general combining ability of BMR sorghum sterile lines AMP454, AMP19, and T98A were relatively high, with the better hybrid combinations being AMP19×ZS-102 and AMP454×ZS-102.