Effects Of Population Improvement By Mass Selection On The Two Synthesized Maize Groups

The introduction and utilization of exotic germplasm contributes to scarcity alleviation of maize germplasm available for breeding in China.Furthermore,effective utilisation of exotic maize germplasm has the potential to improve the quality of main germplasm used for maize elite inbred line breeding,which can be achieved by finding elite maize hybrids from heterotic groups constructed by exotic maize germplasm.The identification of elite maize hybrids is based on a heterotic model developed from the analysis of heterotic groups mentioned above.This experiment was conducted with two synthesized maize populations and their 10 improved populations by five cycles' parental mass selection,and 36 crosses between these 12 populations and three testers based on NCII design,which were provided by Chinese Academy of Agricultural Science.The incomplete diallel crosses were used to study the major agronomic traits and their general combing ability(GCA)effects.The main results were as follows:1.Combined analyses of variance for 23 traits in ZP15 and ZP16 revealed highly significant differences for 100-kernel weight,days to silking,rows per ear,volume weight,ear diameter,ear height,ear length,cob diameter,plant height,moisture.Significant differences were observed for environments in all traits except for kernel row number;highly significant differences were observed for blocks only in ear length and lodging percent;and highly significant differences were observed for genotype × environment interactions in 21 traits.2.Analyses of variance showed highly significant differences for environments and crosses in GCA effects for all traits.Significant differences were observed for cross ×environment interacions in GCA effects for all traits except for ear diameter and moisture;significant differences were observed for different cycles of improved populations in all traits;significant differences were observed for population × environment interacions only in car length;highly significant differences were observed for testers in all traits;and significant differences were observed for tester × environment interacions in in all traits except for moisture.3.After five cycles' improvement of ZP15 by bisparental mass selection,better per se performances were observed for plant height,ear height,moisture,volume weight,100-kernels weight;better GCA effects were observed for plant height,ear height,yield,ear diameter,ear length,100-kernels weight;Better per se performances and GCA effects were observed only for plant height,ear height and 100-kernels weight.4.After five cycles of biparental mass selection,the means of plant height,ear height,the days to silking,the days to powdering,yield,axis diameter,rows per ear,volume weight for ZP16 had good performance.And the general combining ability of plant height,ear height,yield,the days to silking,the days to powdering,moisture,ear diameter,axis diameter,100-kernels weight for ZP16 had good improvement.But just the plant height,ear height,the days to silking,the days to powdering,yield,and axis diameter had good improvement both in per se performances and the general combining ability for ZP16.5.After five cycles' of bisparental mass selection,there were real differences in per se performances and GCA effects for some traits between the improved populations,and environment had strong influence on per se performances and GCA effects.No significant differences were observed for per se performances and GCA effects,because incomplete block design had eliminated the influence of soil fertility on the field data.Biparental mass selection had significant effects on plant architecture.There were different effects of improvement in different populations and different traits in one population.The improvement effect on the same trait is different under different evaluation criteria,and improvemt should be focused on these traits.