Study On The Genetic Relationship Between Alexho High-oil Maize Inbreds And Normal Maize Inbreds And Normal Maize Inbreds Belonging To Different Heterotic Groups

High oil Maize Inbreds are generally developed from high-oil maize populations with broad genetic germplasm.Presently,commercial high-oil Corn Hybrids are all made by crossing normal Maize inbreds with High-oil Maize Inbreds. Studiy on the genetic relationship among different high-oil maize inbrids with the same or different resources,and their genetic relationship with different normal maize inbreds belonging to different heterotic groups have great theoretical and practical utilization in high-oil maize breeding.According to these,the proper mode for cross-making in high-oil maize hybrids could be built,which could direct the high-oil maize germplasm improvement,and thus increase the efficiency in high-oil maize breeding.In this study,9 ALEXHO high-oil maize inbreds introduced from China Agricultural University were chosen and crossed with 21 normal maize inbreds belonging to different heterotic groups and 9 Yugoslavia normal maize inbreds according to NCâ…¡genetic design,respectively.168 and 81 crosses were made and planted with a randomized complete-block experimental design under two environments,in spring and in summer,in 2005.The combining ability and heterosis of three grain quality,seven ear-kernel and five plant traits were analysed.Meanwhile,the genetic diversity among all inbreds were detected using 120 pairs of SSR markers evenly distributed on 10 corn chromosomes.Cluster analysis were conducted,and the correlations among GD,SCA and heterosis,and their correlations with F1 phenotype traits were calculated.Our objectives were to detect the genetic diversity among different high-oil corn inbrids and their genetic relationship with different normal maize inbreds belonging to different heterotic groups,and to explore the utility of SSR molecular markers in heterosis predication of high-oil maize hybrids.Therefore,references could be provided for the establishment of heterotic groups for high-oil maize hybrids,.and the improvement in the breeding level and efficiency.The main results were as follows:1.Combined variance analysis showed that the mean squares due to crosses for all traits,and the mean squares due to environments,cross×environment interactions, female parent,male parent and the female×male interactions for most traits were all significant or highly significant for both sets of crosses.In the total variance,the contribution of female×male interactions were the biggest,indicating that the interaction between the two kinds of inbreds,high-oil and normal maize inbreds, played the most important role for all traits.2.The SCA,total combining ability and heterosis were all greatly different for all crosses between the same high-oil corn inbred with different normal maize inbreds belonging to different heterotic groups or different Yugoslavia normal maize inbreds, and between the same normal maize inbreds with different high-oil com inbreds.But this tendency was different under the two environments.Great consistency was observed between the total combining ability and the numbers of crosses with over-ckeck or over-average heterosis.3.In the two sets of crosses,the GCA of grain yield per plant and kernel oil content were all positively significant for high-oil corn inbred GY246A and three normal maize inbreds,8085tai,246 and P138 under two environments.This reflected that elite crosses with both grain yield and oil content could much more easily made using these four inbreds.The SeA of grain yield per plant and kernel oil content were all positively significant for four crosses,246×GY246B,Q1261×GY246A, 478×GY956 and ZPL06×GY220.Among them,the grain yield per plant of 246×GY246B was the highest with 25.96%higher than the CK hybrid,and its oil content was 6.6%.This cross might have potential utilization in high-oil corn production.4.Using 120 pairs of SSR primers,429 and 376 alleles were identified among two sets of inbreds,29 and 18 inbreds,respectively.The average number of alleles per SSR locus was 3.575 and 3.133 with a range 2 to 9 and 2 to 8.Ploymorphic index content(PIC)value varied from 0.121-0.845 and 0.188-0.837 with an average of 0.56 and 0.52.The average genetic distance among 29 and 18 lines was 0.573 and 0.552 with a range from 0.101 to 0.720 and from 0.101 to 0.701.This reflected that there was great genetic dversity among tested inbreds and the results have representative.5.According to SSR genetic distances,29 inbred lines were divided into 4 groups.There was great genetic diversity among inbreds in the first group,which could be divided into three subgroups,with 87-1,S22,Gai 3,Xu 178,P138,Qi319 and 246 as a subgroup(1-1),Zheng 58,248,478,9058,Huang C and 8984 the second subgroups(â… -2),8085 Tai the third subgroups(â… -3).Five inbreds were included in groupâ…¡,including Zong3,Zheng 653,Chang 7-2,8622 and Luyuan 92.Shen137 and Q1261 were assigned into groupâ…¢.All 8 high-oil corn inbreds were classified into groupâ…£.For the 18 inbreds in the second set of experiment,four groups were diveded,with Yugoslavia inbreds ZPL01,ZPL06,PL09,PL10 and ZPL02 the groupâ… ,ZPL03,ZPL05 and ZPL04 the groupâ…¡,ZPL07 the groupâ…¢,9 high-oil maize inbreds the groupâ…£.The result showed that there were greater genetic diversity between high-oil com inbreds and both normal maize inbreds belonging to different heterotic groups and Yugoslav maize inbreds.The results of classification were consistent with heterotic groups for normal maize inbreds and their pedigrees. Consequently,SSR markers could be used to study the germplasm relationship between normal and high-oil maize inbreds.6.The correlations between GD and SCA,over-check heterosis and F₁ phenotype value were all not significant in the two sets of experiments.Therefore, only molecular marker diversity might not be used to predict heterosis between high-oil maize inbreds and normal maize inbreds with broad genetic germplasm.