Combining ability of resistance to pod shattering and selected agronomic traits of soybean

Abstract

Eight parents Nyala and SB-8, SB-25, SB-93, SB-19, 915/5/12, 835/5/30 and SB-98 were crossed in a diallel mating scheme to generate 28 F1 progenies in a greenhouse at Kabete, University of Nairobi. The F1 and their parents were evaluated at KALRO-Embu and Mwea Research Centers between December 2016 and May 2017. The trials were laid out in an alpha-lattice design arranged in a 6 × 6 pattern with 3 replicates. Data was collected on maturity, plant height, grain yield and pod shattering. General and specific combining ability were determined according to Griffing’s diallel, Method 2. General and specific combining ability (GCA and SCA) were significant (P<0.05) for all the traits indicating that additive and non-additive gene action were important in the inheritance of pod shattering and other traits. GCA/SCA ratio varied from 0.00124 to 0.0742. Although the ratio was higher for pod shattering (0.0742) compared to other traits (less than 0.0132), the ratio in general was close to zero. This indicated that non-additive gene action played a more important role over additive gene action in the inheritance of these traits. Parents SB-93, SB-19, SB-98, 835/5/30 and Nyala, were the best combiners for early maturity. SB-19, 915/5/12, Nyala, SB-93 and SB-98 significantly contributed towards reduced plant height. Parent 835/5/30 followed by SB-8 had the higher GCA gene action thus were the best combiners for high grain yield. Parents SB-8 and Nyala had the highest negative and significant GCA effects for pod shattering indicating that these lines had favorable gene frequencies of resistance to pod shattering. Progenies of SB-25 x SB-8 were the best combiners for pod shattering resistance across environments. This study found non-additive gene action to be more important over additive and suggested that heterosis breeding and selection of late segregating generations would be effective to improve pod shattering resistance ability and other agronomic traits in soybeans.