Analysis Of QTL Mapping For Maize Plant Type Related Traits Based On NAM Population

Corn is the raw material of food,animal feed and energy crops.High yield is the ultimate goal of maize production and the primary goal of maize breeding.Studying the genetic law of plant type related traits can promote the development of high yield breeding of Maize with high density tolerance.In this study,five maize inbred lines CML470,K22,TY2,CML304and CML496 were used to cross with their common parents B73,respectively.Five BC₂F₅populations and a total of 436 families were constructed for nested Association mapping.Phenotypic identification of plant height,ear height and leaf angle was carried out in Changge City of Henan Province and Yushu City of Jilin Province;genetic linkage maps of five populations and integrated genetic linkage maps of NAM population were constructed by9.4K SNP chip;and QTL mapping of plant height,ear height and leaf angle was carried out in two environments.The main results were as follows:1.The correlation analysis among plant height,ear height and leaf angle of five BC₂F₅populations showed that the correlation between plant height and ear height was very significant;phenotypic descriptive statistical analysis,heritability estimation and variance analysis showed that there were wide variations in the phenotype of offspring of five BC₂F₅populations;the heritability of three traits in different environments ranged from 0.46 to 0.88,and the higher heritability showed that 3 individual traits were controlled by genes;plant type traits of five populations were greatly influenced by environmental factors,and there was also an interaction between genotype and environment.The heritability of three traits in maize NAM population ranged from 0.43 to 0.75.The higher heritability indicated that phenotypic variation was controlled by genes.2.The total length of genetic linkage maps of 5 BC₂F₅ populations ranged from1702.48c M to 2518.61c M;the total number of SNP markers ranged from 949 to 1390;and the average distance between adjacent markers was 1.73c M to 2.13c M.The total length of integrated genetic linkage map was 1827.16c M,the total number of markers was 2117,and the average distance between adjacent markers was 0.86c M.The marker distribution of genetic linkage maps of NAM population and five BC₂F₅ populations in maize showed that the marker density at both ends of each chromosome was lower than that at the middle position.3.ICIM was used to locate three plant type traits in five BC₂F₅ populations.The results showed that for plant height traits,13 QTL were detected in five BC₂F₅ populations,and single QTL explained 8.27%～38.80%of phenotypic variation.Three major QTL for plant height were identified as q PH2-2（detected in two environments）,q PH5-1 and q PH5-2,respectively.For plant height,12 QTL were detected in five BC₂F₅ population,and a single QTL explained8.75%～31.86%of phenotypic variation.Four major QTL with high ear height were identified as q EH2-2,q EH2-3,q EH2-4 and q EH2-5（detected simultaneously in two environments）.For leaf angle,14 QTL were detected in five BC₂F₅ populations,and single QTL explained8.70%～31.15%of phenotypic variation.Four major QTL were identified,namely q LA2-1,q LA4-1,q LA2-3 and q LA5（detected in two environments）.4.Using JICIM method to locate and analyze the three plant type traits of NAM population,the results were as follows:18 plant height QTL were detected in NAM population,explaining 22.05%of the phenotypic variation,distributed on chromosomes 1 and 2;24 ear height QTL were detected in NAM population,explaining 29.51%of the phenotypic variation,distributed on chromosomes 1 and 2;14 leaf angle QTL were detected in NAM population,31.65%of phenotypic variations were explained.They were distributed on chromosomes 1,2and 5.The results of three traits showed that plant height,ear height and leaf angle of NAM population were controlled by a large number of minor additive effects.5.Some common QTL were identified in maize NAM population and single population:in bin2.03-2.04 region,nine plant height QTL were detected in NAM population and CML304/B73,K22/B73 and TY2/B73 populations;five ear height QTL in NAM population were detected in CML470/B73,K22/B73 and TY2/B73 populations;six leaf angle QTL in NAM population were detected in TY2/B73 and CML496/B73 populations.In bin1.04,three leaf angle QTL were detected in NAM population and TY2/B73 population.In addition,a large number of micro-effective QTL detected by NAM population were clustered.