The QTL Mapping And Genetic Analysis For The Internode Number Upper Ear In Maize

Lodging will not only cause the huge loss to the maize yield, but also will affect the mechanical harvest of maize. Therefore, lodging is the key limited factor constrainting the maize yield. In addition to being affected by he climatic factor, the resistance of maize varieties is the main reason for lodging. In order to breed new varieties of maize that have strong lodging resistance, breeders and geneticists carry out many studies on the traits of lodging, especially for the plant height, the ear height and the stem toughness, even locating the relevant traits of QTLs, providing the reference for the new lodging-resisitant varieties of maize. However, due to the stem height and ear height show the typical quantitative trait genetic traits and are affected by environmental factors. Therefore, the QTLs located in different environmental conditions are different and hardly applied in breeding. Due to the plant height of maize is composed by two factors, which are the internode number from ground and the average internode length, but the internode number form ground of each maize varieties is stable basically and the average internode length is 10-15cm long. So if the internode number upper ear increased one, the ear height may lower 10-15cm height and can significantly increase the lodging resistance of maize. Besides, although the internode number upper ear of maize show the genetic quantitative trait, the internode number upper ear of each variety is stable basically in different environmental conditions and the trait is easy to survey. Therefore, clarifying the genetic development of the maize internode number upper ear can provide the theoretical basis for breeding the new lodging-resisitant variety of maize. In this study, we use the RIL population and its coordinate“F₂”population from Long Da 108 to analyze the genetic development of maize internode number upper ear, in order to provide the theoretical basis for breeding the new lodging-resisitant variety of maize. The conclusions of this study are as follows:1、The genetic linkage map whit 217SSR markers, which spanned a total length of 2434.2cM with an average of 11.2cM between two markers, was conducted by a RIL populations of nongda108, and the order of markers was basically consistent with the IBM map.2、A set of“IF₂”population including 243 single crosses was constructed through three round of intermating by using 166 RILs. In the“IF₂”population , the homozygous genotypes deriving from parent HuangC were 8.00%-50.62% and the average was 24.72%; the heterozygous genotypes were 35.81%-62.86% and the average was 49.48%.; the homozygous genotypes from Xu178 were 8.25%-50.62%, and the average was 25.81%. The genotypes of HuangC, heterozygosity and Xu178 at the marker loci followed 1:2:1 theortical ratio, so the genetic components and gene frequency in“IF₂”population were similar as the“F₂”population.3、In three locations, the mean value of internode number upper ear in RIL population,“IF₂”population and the hybrid Nongda108 were all higher than parents. Like the other characters, the internode number upper ear also showed heterosis; the mid-parents heterosis of“IF₂”population had a lage range, from negative heterosis to positive heterosis. Respectively, the range of mid-parents heterosis in Anyang and Xuchang was 15.5% -28.85% and 14.22%-40.88% and the average was 3.52% and 10.33%.4、QTL analysis were conducted by composite interval mapping, three dominant QTL were identified in“IF₂”population, one of a superdominant QTL, three QTL were on chromosome 6, the contribution rate of three QTLwere 9.92%、11.96%、7.26%。One QTL was identified in RIL population on chromosome 1, the contribution rate was 22.14%.