Analysis Of Genetic Basis About Yield Related Traits During Maize Suwan Germplasm Improvement

In this study,different improvement generation derived from the tropical and temperate maize germplasm populations Suwan1,Suwan-Lancaster1,Tuxpeno-Reid1 of,inbred linesof PHB1M,QB446,QB408,QB1013,PH6WC,5311 and its hybrids were used as experimental material.Based on 13 main agronomic traits'evaluation,the combining ability,Heterosis and recurrent selection effect of Suwan germplasm and its derived population were analyzed main conclusions were showed as follows:1.For Suwan1,Tuxpeno-Reid1 and Suwan-Lancaster1 populations,during the improvement process,it showed that with the increase of improvement generation,plant height,ear height and kernels per row showed a growth trend,100-kernel weight and bald tip length showed a decreasing trend.With the introduction of Lancaster germplasm into Suwan germplasm,the introduction of Suwan Lancaster germplasm,plant height and ear height were significantly reduced,ear length and kernel rows per ear were significantly increased,and the period of tasseling and the silking period were significantly shorted.2.The results of general combining ability analysis show that,for Suwan1 group,along with the increase of selection times,tasselling days,pollen-shedding days,silking days,plant height,leaf number above the ear,ear length,kernel rows per ear,plot yield of GCA?general combining ability?was improved obviously;however,for inbred line of PHB1M and synthetic group Suwan-Lancaster1:tasselling days,pollen-shedding days,silking days,plant height,ear height GCA effect was significantly lower than that in Suwan1 groups,GCA of ear length,kernels per row for the positive effect value.These results showed that Lancaster germplasm had better effect on late maturity of improved Suwan germplasm.3.After 3 half sib reciprocal recurrent selection,Suwan-Lancaster×Tuxpeno-Reid hybrid combination of ear length,row number,kernels per row of the average heterosis was significantly increased,the average heterosis of 100-kernel weight and bare tip length was significantly decreased.Especially,the reduction of average heterosis of bald tip length is one of the important reasons for the increase of grain yield.In the process of improvement,bald tip length of Suwan-Lancaster1C₀ was decreased from 2.36cm to 1.71cm of Suwan-Lancaster1C₃,bald tip length of Tuxpeno-Reid1C₀ was decreased from 1.5cm to 1.08cm of Tuxpeno-Reid1C₃,bald tip length of Suwan-Lancaster1C₀×Tuxpeno-Reid1C₀ has decreased from 2.64cm to 1.56cm of Suwan-Lancaster1C₃×Tuxpeno-Reid1C₃,with a reduction of 1.08cm and a decrease of 40.91%.the grain yield of Suwan-Lancaster1C₀ was increased from 478.64kg/mu to 520.69kg/mu of Suwan-Lancaster1C₃,which increased by 8.79%and reached a significant level?P=0.05?.However,the grain yield of Suwan-Lancaster1C₀×Tuxpeno-Reid1C₀ was increased from 545.46kg/mu to620.7kg/mu of Suwan-Lancaster1C₃×Tuxpeno-Reid1C₃,increment reached 75.24kg/mu,the genetic gain was 13.79%,reached a significant level?P=0.05?.4.The genetic distance analysis showed that,for Suwan1,Suwan-Lancaster1 and Tuxpeno-Reid1 groups,with increase of improvement generation,the genetic distance between each two improved generations showed a gradually decreasing trend.In addition,according to the division result clustering analysis of genetic distance data and principal component,the 19accessions were divided into 7 categories.The first group includes Suwan1C₁₀,Suwan1C₁₁,Suwan1C₁₂,Suwan1C₁₃,Suwan1C₁₅,QB446,QB408,belonged to the Suwan groups.The second groupincludesSuwan-Lancaster1C₀,Suwan-Lancaster1C₁,Suwan-Lancaster1C₂,Suwan-Lancaster1C₃,belonged to the Suwan-Lancaster groups.The third group is only 5311,which belongs to the local germplasm group.The fourth group includes Tuxpeno-Reid1C₀,Tuxpeno-Reid1C₁,Tuxpeno-Reid1C₂,Tuxpeno-Reid1C₃,belonged to the Reid-Tuxpeno groups.The fifth group was PH6WC,belonging to the Ried groups.The sixth group is QB1013,which belongs to the X series.The seventh group is PHB1M,belonged to Lancaster groups.The result of cluster analysis is basically consistent with the source of pedigree.5.Genotype analysis showed that during the process of improvement,the recurrent selection in groups made fewer fragments of gene exchange and recombination,and the recurrent selection among groups made the frequency of gene exchange and recombination relatively high.Among them,we screened 12428 stable genetic markers in different modified generations of Suwan1population,there are 12 specific markers,respectively in the first,third,sixth and eighth chromosomes,with sixth chromosome polymorphism is highest.We selected 9387 stable genetic markers in different modified generations of Suwan-Lancaster1 population,and 21 specific SNP markers were distributed in first,second,third,fourth,fifth,sixth,seventh and ninth chromosomes,and the second chromosome polymorphism is the highest,exchange high recombination frequency.We screened 12456 stable genetic markers in different modified generations of Tuxpeno-Reid1population,there are 24 specific markers,distributed in first,second,third and tenth chromosomes.In addition,based on SuwanC₁₁ groups of SNP markers,screened 6364 stable genetic markers in different modified generations of Suwan-Lancaster1 population,and 60 specific markers were obtained,which were distributed on the chromosomes of the genome.6.The mixed linear model combined analysis of 43980 SNP markers?MAF>0.05?and yield related traits.The results showed that 13 SNP loci significantly associated with ear length traits were found in the Suwan1 and its derived population,located on the first,second,fifth,seventh,eighth and ninth chromosomes,there are 1 SNP loci located in the specific genetic segment of Suwan-Lancaster population.There were 16 SNP loci significantly associated with kernel rows per ear,located in second,third,fifth,sixth,seventh,eighth and ninth chromosomes,there are 2SNP loci located in the specific genetic segment of Suwan-Lancaster population.