| Maize has been widely used as food,feed and industrial raw materials.The reason of sustained increases in maize yield is the adaptation of commercial hybrids which have been applied in worldwide.Heterosis,as a main way to improve maize yield,is under the investigated for a dozen of decades.Although several hypothesis for explaining the genetic mechanism responsible for heterosis have been postulated and are still under the debate,application of heterosis in maize have been practiced and harvested the constant genetic gains in yield.Distinguishing the heterotic groups in a collection of elite inbreds and making the inter-groups' crossed can significant enhance the yield and improve the efficiency of maize breeding.In the previous studies,SSR markers,the prevalent markers,have been applied extensively in the field of genetic diversity analysis and classification of heterotic groups.However,the unspecific and undistinguished SSR bands have hampered their further use.In this study,we employed the InDel markers in clustering heterotic groups and validated their efficiency and accuracy in maize.InDel loci are predominate and more widely distributed on maize chromosome than SSR loci.However,the InDel loci related to heterotic group are not very clear yet.As the first step,we determine the candidate heterotic loci using 453 stiff stalk(SS)and non-stiff stalk(NSS)inbreds'resequencing data.According to the loci information showing the significant frequency differentials between SS and NSS groups,we developed hundreds of InDel markers which have loci specificities.A total of 258 InDel markers were used for classifying 143 domestic inbred lines into SS or NSS heterotic groups.The results are congruent with the pedigree if they have.Moreover,we selected some inbreds belonging to inter-and intra-groups and made 93 crossing combinations.The combinations are including:SS×SS,NSS×NSS,SS×NSS and NSSXSS.The overall grain performances of F1 hybrids were compared and the results were presented.1)Based on the re-sequencing data of SS and NSS,1000 candidate regions associated with heterosis were obtained through Fisher exact test.Then 258 InDel markers distributing on 10 chromosomes in these regions were developed for genetic diversity analysis of 143 maize inbred lines.Totally 559 alleles were detected by 237 InDel markers,and the PIC ranged from 0.123 to 0.665,with the average of 0.455.As the result of the genetic diversity study,64 inbred lines included standard testers Mo17?Chang7-2?Huangzaosi were clustered into NSS group and the other 79 inbred lines included B73?Zheng58 were clustered into SS group.2)61 divergent inbred lines were selected and 61 F1 hybrids were derived from the cross between SS and NSS,as well as 32 F1 hybrids within SS or NSS.Correlations were analyzed between yield and some other agronomic traits,including ear weight?row number?ear length?kernel length?kernel perimeter?1000-kernel weight?Length-to-width ratio?kernel width?grain number per row.All these 9 traits have a positive correlation with grain yield,but some traits showed higher correlation with yield while some with lower correlation.The order of correlation from strong to weak is:ear weight?row number?ear length?kernel length?kernel perimeter?1000-kernel weight?Length-to-width ratio?kernel width?row number.3)According to the phenotype data of these F1 hybrids,6 traits(ear length?ear weight?kernel length?kernel perimeter?1000-kernel weight?kernel weight per ear)from the interheterotic group cross were significantly higher than those from intraheterotic group corss.The result indicate that these InDel molecular markers associated with heterotic loci could facilitate molecular maker-assisted breeding and heterosis study in maize. |
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