Genetic Analysis On Plant Height And Ear Height Of Elite Maize Hybrid Zhengdan 958

It is used in Huanghuaihai ecological zone in China that is the major maize heterotic groups with Reid, Tangsipingtou and Tem-tropic I groups. Tangsipingtou group with its representative line Huangzaosi paly a major role in maize breeding in China. An elite inbred line, Chang 7-2, with many good traits such as resistance to stress, good adaptation and high general combination ability, have been widely used in maize breeding program in China. One hybrid, Zhengdan958 derived from Chang 7-2, has been registered in Henan, Hebei, Shangdong provinces and Ministry of Agriculture. Up to now, it has been the leading hybrid with the largest planting area and remarkable economy benefits. In this study, the components of yield were analyzed using F_2:3 population derived from Chang 7-2 and Zheng 58, especially emphasized on palnt height and ear height in maize. Genetic analysis and QTL mapping of these traits will facilitated the marker-assisted selection(MAS) in maize breeeding program. The main results were as following:A genetic map was constructed using 180 SSR markers, which covered 10 chromosomes of maize; the total linkage length of the map was 1987.7 cM, with 11.0 cM average distances between two markers. Compared with the IBM map from MaizeGDB website, there were the similar order of the markers on ten chromosomes. The largest linkage distance between the two markers is 13.58 cM, and the smallest linkage distance between the two markers is 8.63 cM.The phenotype data of from 225 F_2:3 families lines and the two parental lines were gotten under 5 environment in year 2007 and 2008. Normal distribution was observed both in plant height and ear height among F_2:3 families lines. Most of the variation was devoted by the genetic factors, with a high broad heritability of 60% and 56% for plant height and ear height, respectively. Using composite interval mapping with mixed model, main genetic effect including epistasis and epistatic×environment interactions were analyzed in F_2:3 population descended from the elite hybrid, Zhengdan958. Totally three stable QTL were identified for plant height, one of them on chromosome 5, qPH5-1 with flanking markers umc2302-umc1800 ,were consecutive detected in all five environments, which account for 8.0%-17.5% genetic variation. The qPH1-1 and qPH2-1 with flanking markers umc1703-umc1590 and dupssr25-phi090, were detected in five environments except Xichang location in 2007, which account for 8.0%-11.5% and 5.0%-8.0% genetic variation. In all the loci detected for plant height, the loci from Chang7-2 is in the direction of increasing the trait. The additive effects, partly dominant effects and over- dominant effects paly the major roles for the genetics of plant height in maize.Totally three stable QTL were detected for ear height, one of them on chromosome 1, qEH1-1 with additive effect, were detected in three environments, which account for 6.2%-10.1% genetic variation. The other QTL, qEH5-1 was also detected in three environments, which showed partly dominant effects and over- dominant effects, and can account for 7.0%-8.7% genetic variation. The third QTL, qEH3-1, was detected in two environments, which account for 5.9%-6.5% genetic variation. In all the loci detected for plant height, the loci from Chang7-2 is in the direction of increasing the trait. Morever, other QTL for ear height were also found in single environment.For epistasis and epistasis×environment interactions, four pairs of epistatic interactions interacting with each other for plant height, were mapped on chromosomes 1, 2, 5 and 8, respectively. Generally, all patterns of interactions were detected, which included AA (2 pairs), AD/DA (1 pair) and DD interactions (1 pair). It should be noted in these digenic interactions, one pair interaction between dupssr25-phi090 and umc2302-umc1800 on chromosome 2, has the largest genetic effects and can account for 3.5% phynotypic variation. The significant interactions observed in this study belong to QQ type (two interactive loci linked with two QTL). Eight pairs of epistatic interactions interacting with each other for ear height, were mapped on chromosomes 1, 2, 3, 5, 6 and 7, respectively. Generally, all patterns of interactions were detected, which included AA (3 pairs), AD/DA (2 pairs) and DD interactions (2 pairs). It should be noted that one pair interaction between dupssr25-phi090 and phi090-umc1525 on chromosome 2, has the largest genetic effects and can account for 5.4% phynotypic variation. However, significant interactions in the NN group(none of two interactive loci linked with any QTL) and QN (one of two interactive loci linked with a QTL) was also observed for ear height. These results indicated that some single locus usually had no noticeable effect on phenotype, but could still significantly affect the trait in two-locus interactions.