| Maize is a typical cross-pollination crop.It is a classical method to make use of corn heterosis by combining different inbred lines and breeding excellent hybrids.Therefore,the study on the breeding potential of new inbred lines is of great practical significance to guide maize breeding.This study takes 13 new inbred lines,8 widely used inbred lines and5 standard inred lines as materials to compare the genetic differences among different lines by using phenotypic identification and SSR markers;and mating 210 combinations by the Griffing Method Ⅳ to analyze the yield combining ability and heterosis,so as to clarify the breeding potential of the new inbred lines,and provide reference for further rational application or improvement.The main findings are as follows:1.The phenotypic identification results indicate that the silking period of 13 new inbred lines varies from 72 days to 86 days,the average plant height is 151.67 cm to 250.00 cm,and tassel branches is 2.07 to 14.30.Wherein,K962 and K31 are higher,245 cm to250cm;K324 and K111 are shorter,150 cm to 160 cm.The yield per plant varies rom 53.13g～ to 111.26 g.Wherein,K311 has the highest yield,significantly higher than that of 4widely used inbred lines such as 698-3,and the yield component traits such as kernels per row,ear length and 100-kernel weight are better.The next is K351,it has better seed-producing rate and 100-kernel weight.K492 has the lowest yield,and the most of the yield component traits are also worst.The average yield per plant of other inbred lines is above 70 g,and the yield component traits are also better.Taken together,K311 and K351 are new inbred lines with excellent characteristics per se.2.According to results of SSR marker analysis,173 genotypes have been detected in26 inbred lines,averagely 4.325 in each primer,and 191 alleles have been detected,averagely 4.775.Taking the genetic similarity coefficient 0.696 as the threshold,26 inbred lines can be divided into 8 groups by UPGMA method,that is,5 common groups and 3new groups,and the clustering results are basically in agreement with pedigree sources.The inbred lines of the 5 groups account for 53.85%,and that of the 3 new groups account for 46.15%.Among them,10 new inbred lines including K115 are divided into the 3 new groups.It is thus clear that these new inbred lines expand the maize germplasm base in China.3.The results of combined variance analysis show that the yield per plant of 210 combinations has significantly differences,and the interaction effects between combinations and environments is also significant;the interaction effects of yield GCA,SCA,GCA and environments is extremely significant,and the interaction effects between SCA and environment is at significant level.The results of combining ability effect value analysis show that the average yield GCA effect value of the new inbred lines is significantly higher than that of the widely used lines.In Shuangliu site,the yield GCA effect values of 4 new inbred lines including K143 reach the positive significant level,while the yield SCAs of 15 combinations mated by new inbred lines such as K6×K143reach the positive significant level.In Xuanwei site,the yield GCAs of 6 new inbred lines including K61 reach the positive significant level,and the yield SCAs of 11 combinations mated by new inbred lines such as K351 × K115 reach the positive significant level.According to the comprehensive analysis,the new inbred lines K61,K143 and K115 are inbred lines with high yield combining ability.4.The heterosis analysis found that the yield hrterosis of 210 combinations varies from-58.69% to 35.12% in Shuangliu site.Wherein,there are 50 combinations with yield increase and 18 combinations with yield increase significantly,accounting for 22.86% and8.57% of total combinations respectively.The yield heterosis varies from-76.58% to31.19% In Xuanwei site.Wherein,there are 11 combinations with yield increase and 3combinations with yield increase significantly,accounting for 5.24% and 1.43%respectively.The yield of combination K61 × K143 increases significantly in both experiment sites,showing an average yield increase of 33.16%,good comprehensive characters and strong adaptability.It is recommended to a higher-level trial.5.In conclusion,the new inbred lines K61,K143 and K115 have high yield GCA,and K61 and K115 have novel germplasm.The 3 inbred lines have high yield,and most of the agronomic characters are good,so they are ideal parents for high yield breeding.K311,K962 and K365 have high yield GCA and good agronomic characters,K311 and K365 have novel germplasm.They are of high yield breeding potential,but the plants are higher and need to be further improved.The yield GCA of the other 7 new inbred lines,such as K492,almost shows significant negative effects,and have some defective characters including low yield,but they could be further improved and utilized as germplasm resources by using good characters including dwarf. |
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