Genetic Analysis And Identification Of Quantitative Trait Loci(QTLs) For Drought Tolerance In Maize (Zea Mays L.)

Maize is an important crop in china .Water availability is one of the major limiting factors for maize growth. In China, maize is grown mainly under drought conditions (Northern-Western China), there were about 10%-30% maize yield losses.It is a big challenge for breeders to improve and develop drought tolerance cultivars.Drought tolerance is a trait that is influenced by multiple genes. It is not very efficient to improve drought tolerance of maize hybrids by traditional methods. A population of 234 F2 plants, derived from the cross X178×B73, was used in this study. X178 is an elite inbred line widely utilized in China. Field experiments had been done in Linfen ,Shanxi and Sanya, Hainan. QTLs for flowering time, yield, plant height and ear height were identified by using SSR markers. The consensus in results of QTLs location among difference genetic background was discussed. The aim of current study was to explore genetics base on drought tolerance in maize and gain useful molecular markers for molecular-assisted slection. The results are as following.1. The linkage map including 121 SSR markers covered 1379.5 cM in length with an average marker interval of 11.4cM, minimal interval of 1.3 cM and maximal interval of 35.7cM. The order of markers in this map was identical to the order of corresponding markers in IBMmap and their bins on the chromosomes.2. Ratio of segregation distortion among SSR markers was 12.4% in F2 population. Several loci for segregation distortion were identified. Influence of segregation distortion on the result of QTL analysis.3. Under well-watered condition, Six QTLs for male flowering time, 6 QTLs for female flowering time, 4 QTLs for anthesis-silking interval, 3 QTLs for yield, 5 QTLs for one hundred kernel weight, 4 QTLs for kernel number per ear, 3 QTLs for kernel weight per ear. 3 QTLs for ear weight, 5 QTLs for ear number per plant, 16 QTLs for plant height and 11 QTLs for ear weight.4. Under water-stressed condition, 9 QTLs for male flowering time, 6 QTLs for female flowering time, 6 QTLs for anthesis-silking interval, 1 QTLs for yield, 5 QTLs for onehundred kernel weight, 2 QTLs for kernel number per ear, 1QTLs for kernel weight per ear, 4 QTLs for ear weight, 2 QTLs for ear number per plant, 17 QTLs for plant height and 10 QTLs for ear weight.5. It was revealed that thirty eight QTLs referred to drought tolerance in maize by comparing the difference between QTLs detected under both well-watered and water-stressed condition, of which 6 QTLs for male flowering time, 2 QTLs for female flowering time, 4 QTLs for anthesis-silking interval, 1 QTLs for yield, 4 QTLs for one hundred kernel weight, lQTLs for kernel number per ear, 1 QTLs for kernel weight per ear, 5 QTLs for cob weight per ear , 3 QTLs for ear weight, lQTLs for ear number per plant, 5 QTLs for plant height and 6 QTLs for ear weight.6. Two-way ANOVA showed that interaction between pair of marker loci contributed to phenotype of trait. It was suggested that the epistasis contributed to the phenotypic variation of plant height. 17 and 38 pairs of loci influenced significantly plant height under well-watered condition, according to field data from Linfen and Sanya respectively, 20 and 47 pairs of loci underwater-stressed condition, as well.7. It was suggested that heterozygocity played an important role in heterosis. The result showed that correlation coefficient between plant height and general heterozygocity was lower than that between plant height and specific heterozygocity.