Genetic Analysis Of Maize Inbreds Of Shaan A And Shaan B Populations Under Different Density Condition

The objective of this study was to investigate the effectiveness of high-density breeding strategy through analyzing genetic components and general combining ability effects(GCA)under different density.Seventeen maize inbred lines selected under high density were test-crossed with two testers(Zheng 58,Chang 7-2)in the North Carolina Design II.Thirty-four crosses were evaluated under different density conditions(45 000,67 500,90 000 plants ha-1)in 2014 and 2015 at Yangling,Changwu and Yulin in Shaanxi province.The genetic variance components for grain yield and density tolerance traits were estimated using PROC VARCOMP method.Frequency distribution was used to analyze the response of GCA for grain yield and density tolerance traits under different density.The stability of maize inbred lines and crosses were evaluated based on AMMI model.The results showed that:1.The heredity of grain yield and other traits was controlled by additive and nonadditive genes.The additive variance accounted for 23.86%~47.20% of the total variation for sterile plant rate under different density conditions,indicating that non-additive gene action largely controlled the inheritance of sterile plant rate.While,grain yield,stalk lodging rate,RPS of 3rd internode and ear internode,plant height,and ear height were mostly controlled by additive gene action,for which the additive variance accounted for 55.23%~97.58% of the total variation under different density.Also,the contribution of additive gene action to total variance increased with the increasing of planting density.2.The grain yield and density tolerance traits tend to normal distribution under different density.The high plant density selection method gained a good result for grain yield and density tolerance traits.The average of general combining ability for grain yield,sterile plant rate,stalk lodging rate,RPS of 3rd internode,plant height and ear height increased by 0.28,-0.21,-0.03,0.02,-0.16,1.09 respectively from low density to high density.3.The correlations between GCA of the inbred lines and their crosses were significant(r=0.877**,r=0.811**,r=0.672**)under different density.Grain yield increased at every planting density.Differences in the linear regression coefficient across densities were significant(P<0.05).To improve maize yield,we should strengthen density tolerance selection for adapting to natural selection,improve lodging resistance traits of maize population at high plant density.4.The number of stable inbred lines was 9,8,and 14 respectively,which accounted for 52.94%,47.06%,and 82.35% of the total inbred lines under different density conditions.The number of stable crosses was 24,24,and 28 respectively,which accounted for 70.58%,70.58%,and 82.35% of the total crosses under different density conditions.As the density increases,the number of stable maize inbred lines and crosses was increased.5.There were 9,10,10 maize inbred lines that show positive effects for grain yield and density tolerance traitsin three density conditions.Also,the GCA effects for grain yield of the inbred lines KA105,KB043,KB109,KB014,KB081 and YLB-6 increased with the increase of planting density,with increased grain yield,reduce the empty rod rate,reduce the lodging rate,improve the characteristics of stem strength.6.The SCA effects for grain yield of inbred lines from Shaan A group with Chang 7-2 were 0.44,0.37,and 0.70 respectively under different density,indicating that there was stronger heterosis between Shaan A group and Chang 7-2.The SCA effects for grain yield of inbred lines from Shaan B group with Zheng 58 were 0.42,0.49,0.51 respectively under different density,indicating that there was stronger heterosis between Shaan B group and Zheng 58.