| Evaluation of germplasm genetic diversity, study of genetic relationship and heterosis among germplasms are important parts of maize breeding research. The paper studied genetic diversity and heterotic groups classification, relationship between genetic diversity and heterosis by SSR molecular marker in 17 excellent materials and maize inbred lines with potential of application, using SSR molecular marker on 7 national standard testers. At the same time, studied combining ability, genetic parameters, correlation analysis, path analysis and heterosis of 119 Group portfolio.The main results are as following:1. By analysing 24 maize inbred lines with SSR,136 alleles was detected from 44 pairs of primers,2-7 alleles of each pair, average was3.09. It indicated SSR markers could detect genetic diversity of maize inbred lines in molecular level.2. Calculated SSR similarity coefficient and genetic distance by method of Nei-lis, the genetic distance cluster showed that 24 inbred lines could be divided into 7 categories with the standard genetic distance was 0.65, clustering results were consistent to the most of the known genealogical source relations of maize, genetic distance among cluster groups was greater than that within group, the results showed SSR markers could be used for division of maize heterosis.3. Analysing combining ability could find that:there was significant difference among 20 traits of 24 inbred lines and the preparation combination. Performance of the yield traits of each hybrid combination was consistent with the general combining ability, so general combining ability could be used to predict yield. Heterosis analysis showed that, from the view of general combining ability of 119 cross combinations, performaned well were Ye 478×Yu 561, Huang zaosi×Yu 549, B73×Jiao 51, Qi 319×Yu 561, Ye 478×Jiao 51, Zi330×Yu561, Ye 478×AM330, Zi 330×87-1, Ye 478×B110, Qi 319×Yu 268, Huang zaosi×B119.4. Estimation of population genetic parameter indicated that:the order of the variance of each trait GCA Vg (%) was reverse to SCA Vs (%), the other traits of GCA variance were greater than SCA variance excepting kernel weight per ear, ear weight and plot yield, which indicated heterosis of these traits were showed mainly by additive genetic effects, and non-additive genetic effects were relatively weak. The broad and narrow heritability of ear height, plant height, tasseling date, silking date, rows per ear, seed length, ear length, ear diameter, ear yield rate, single cob diameter, kernel number per row, seed set, single cob weight, sterile length were high, and appropriate for early generation selection.5. According to the correlative analysis,10 traits of ear length, ear diameter, seed length, seed set, kernel number per row, grain depth, single cob weight, ear weight,1000-kernel weight and ear yield rate were positive significant correlation with yield per plot, ear height and single cob diameter significantly correlated with plot yield.6. Path analysis showed that:the order of direct contribution of traits to yield and kernel weight per ear was ear weight> seed set> ear yield rate> ear length> grain depth> 1000-kernel weight>kernel number per row> ear diameter> single cob weight. Among them, the direct effects of ear weight, seed set, ear yield rate, ear length and grain deep on kernel weight per ear were positive effects,1000-kernel weight, kernel number per row, ear diameter and single cob weight were negative effects.7. According to incomplete diallel crosse design,24 inbred lines was matched to 119 hybrid combinations, then divided into 6 categories by the method of UPGMA with the distance of yield specific combining ability, the classification results were basical accord to inbred genetic relationship, specific combining ability between the groups was greater than within.
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