QTL Analysis for Plant Height with Molecular Markers in Maize

Plant height has become one of important agronomic traits with the increase of planting density recently and the rapid developments of molecular markers have provided powerful tools to localize important agronomic QTL at the genomic level. The purposes of this investigation are to map plant height QTL with molecular markers and to analyze their genetic effects in maize. An F 2∶3 population from an elite combination (Zong3×87-1) was utilized for evaluating plant height in two locations, Wuhan and Xiangfan, with a randomized complete block design. The mapping population included 266 F 2∶3 family lines. A genetic linkage map, containing 150 SSR and 24 RFLP markers, was constructed, spanning a total of 2 531.6 cm with an average interval of 14.5 cm. Totally 10 QTL affecting plant height were mapped on six different chromosomes with the composite interval mapping. Seven of 10 QTL were detected in two locations. The contributions to phenotypic variations for the single QTL varied between 5.3 and 17.1%. Additive, partial dominance, dominance, and overdominance actions existed among all detected QTL affecting plant heights. A large number of digenic interactions for plant height were detected by two-way analyses of variance. 107 and 98 two-locus combinations were found to be significant at a 0.01 probability level in two locations respectively. 23 of them were simultaneously detected in both locations. They accounted for phenotypic variations of 4.511%. It was noticed that a locus, umc1122, had digenic interactive effects with other four different loci for plant height, which distributed on three chromosomes. A few of plant height QTL was involved in significant digenic interactions, but most significant interactions occurred between markers that are not adjacent to mapped QTL. These results demonstrated that epistatic interactions might play an equal importance role as the single-locus effects in determining plant height of maize.

Dynamic analysis of QTL for plant height at different developmental stages in maize(Zea mays L.)

Plant height in maize is not only one of impor-tant agronomic traits, but also one of model traits suitable for study of developmental biology. Using data from field tests in two locations (Wuhan and Xiangfan) within the same year and a molecular linkage map covering all of 10 chro- mosomes, QTLs affecting plant height at five different de- velopmental stages were mapped and analyzed by the com- bination of composite interval mapping and the conditional analysis method. Eight QTLs for plant height at different stages were located at different regions of five chromosomes (LOD≥2.5). The results showed that there were different effect values of QTL on plant height at different develop- mental stages. Three QTLs were detected at all of five stages. With different stages, contributory percentage of single QTL to plant height varied between 3.8% and 17.1%. It suggested that the expression of each QTL controlling plant height was different at different stages. With net growth, seven condi- tional QTLs for plant height were detected. Conditional QTLs were nearly detected at each stage, and QTLs of Ph1-1, Ph1-2, Ph3, Ph5-2 and Ph9 were detected at both locations (Wuhan and Xiangfan). The contributory percentage of sin-gle conditional QTL to plant height varied between 3.8% and 12.3%, indicating that QTLs for plant height are ex-pressed in different time-space. Therefore, QTL expressed at different stages should be considered when marker assistant selection is conducted for quantitative traits.