Characterization Of Genetic Variation Of Five Maize Germplasm Populations

The narrow base and inefficient use of maize germplasm in China has been one of the majorfactors limiting maize breeding progress. It is of great importance for effective utilization of maizegermplasm to characterize genetic variation and heterotic relationships among populations. In the study,five populations (Csyn5, Csyn6, Csyn7, BSSS, and Suwan1) representing the main maize germplsmgroups in China were chosen as experimental materials and10diallel crosses were designed accordingto Griffing IV. Genetic relationships among the populations were studied through analyzing combiningability, heterosis, and genetic diversity of the populations, and genetic variation of the populations wascharacterized to provide base for maize germplasm improvement. The major findings were as follows:1. There were fine general combining ability (GCA) effects of the five populations for severalagronomic traits in Northeastern China and the Yellow and Huai River Valleys of China, which showedgreat utilization potential in the populations. For Csyn5, GCA effects for hundred-kernel weight andgrain yield in the Yellow and Huai River Valleys of China and those for ear row number in bothenvironments were extraordinary. For Csyn6, GCA effect for kernel number per row in the Yellow andHuai River Valleys of China and those for grain yield in both envirenments were excellent. For Csyn7,GCA effect for kernel number per row in the Yellow and Huai River Valleys of China and those forhundred-kernel weight and grain yield in both envirenments were outstanding. For BSSS, GCA effectsfor kernel number per row in both envirenments were distinguished. For Suwan1, GCA effect for daysto silking in the Yellow and Huai River Valleys of China and those for plant height in both environmentswere relatively high.2. Cluster analysis based on specific combining ability (SCA) effects for grain yield indicated thatthe five populations could be classified into three groups: Group I included Csyn5, Group II includedCsyn6and Suwan1, and Group III included Csyn7and BSSS.3. The relatively strong heterosis in crosses such as Csyn7×Csyn6, Csyn7×Suwan1, Csyn5×Csyn6,and Csyn5×Csyn7demonstrated that strong heterosis was apt to occur between inter-group populations.4. Gene diversity (D) of Csyn5, Csyn6, Csyn7, BSSS, and Suwan1was0.35,0.34,0.43,0.36, and0.39, respectively. According to modified Roger’s distance (MRD), genetic distance between Csyn5andCsyn6, Csyn6and BSSS, was the largest (0.54); that between Csyn5and BSSS, BSSS and Suwan1wasrelatively large with0.52and0.51, respectively; that between Csyn6and Csyn7was the smallest (0.40).Cluster analysis and principle component analysis based on MRD manifested that the five populationscould be assigned to three groups: I. Csyn5; II. Csyn6, Csyn7, and Suwan1; III. BSSS.5. Integrating SCA effects for grain yield, heterosis and genetic diversity of the populations, itcould be determined that there was relatively close genetic relationship between BSSS and Csyn7,Csyn6and Suwan1; there was relatively distant one between BSSS and Csyn6, BSSS and Suwan1,Csyn7and Csyn6, Csyn7and Suwan1, Csyn5and the four other populations. Differentiation of allelefrequencies between populations indicated that if genetic relationship between two populations was more distant, the allele frequencies were more variable and the the number of alleles whose frequencydifference was relatively large accounted for more proportion and vice versa. These alleles may beimportant genetic basis for heterosis among the populations.