Construction Of Linkage Genetic Map And Detection Of QTL For Seven Agronomic Traits Including 100-seed Weight In Soybean (Glycine Max L. Merr.)

Genetic linkage map provide a powerful tool for structure analysis and comparison of plant genome. High-density molecular map can be effectively applied to map quantitative trait loci (QTL), map-based cloning of genes, research of comparative genomics and molecular marker-assisted breeding. Many agronomic traits including yield-related traits are quantitative traits, genetic investigation for these traits is great significance on the basis of genetic linkage map.In this study the molecular marker information of 244 and 260 F2 plants from direct and reciprocal crosses between Lishuizhongzihuang and Nannong 493-1 were used to construct the genetic linkage maps using the software of JoinMap 4.0, respectively. Some agronomic traits-100-seed weight, plant height, pod-seeting height, branches number, stem diameter, harvest index and seed-stem ratio-for the 504 F2:4 families were measured simultaneously at Jiangpu experimental station and Linyi experimental station in 2008. The above information was used to detect QTL for the above traits using multi-QTL joint analysis (MJA) along with composite interval mapping (CIM) and to estimate all kinds of effects-main effect, cytoplasmic effect, environmental effect, cytoplasm-by-QTL and environment-by-QTL interaction effects. These detected QTL for plant hight in this study along with the trait QTL identified by other groups were used to carry out Meta analysis using the software of BioMercator 2.1. The results were as follows.First,113 SSR markers of 150 SSR markers were mapped into 34 linkage groups, assigned to 19 chromosomes in soybean according to the public genetic map in soybean, except for linkage group B1. The total length of linkage maps was 1557.85cM, with an average marker spacing of 13.79 cM. The number of markers on each linkage group was from 2 to 10, and the length for each linkage group was from 6.9 to 109.1 cM. As compared with the public genetic map, the marker order in linkage groups Al, A2, B2, C1, C2, Dla, D1b, E, G, I, K and L were almost same, except for a few markers, such as Satt226, Satt514 and Sat₃62. This indicates that the linkage genetic map in this study is suitable for the inheritance analysis of quantitative trait. Then, ten main-effect QTL (M-QTL) for 100-seed weight were commonly detected by the MJA and CIM, where three QTL, qSW-6-2, qSW-20 and qSW-10-4, with the heritabilities of 6.41%,14.68% and 8.06%. were identified repeatedly 2 to 3 times in different populations. Six M-QTL for plant height were commonly detected by the MJA and CIM, and the heritabilities of four QTL, qPH-2, qPH-17-4, qPH-16 and qPH-X2, were more than 10%. One M-QTL for pod-seeting height, qPSH-2, was commonly detected by the MJA and CIM, and in the two F2:4 populations from direct and reciprocal crosses at Linyi experimental station, along with the heritabilities of 6.60% and 42.28%. Two M-QTL for stem diameter, qSD-1 and qSD-7, with the heritabilities of 21.60% and 11.26%, were commonly detected by the MJA and CIM. The environment-by-QTL for branches number, qBN-18e, detected by the MJA, were consistent with the M-QTL identified by the CIM. Three M-QTL for harvest index, qHI-14, qHI-1 and qHI-7-2, with the heritabilities of 13.43%,47.63% and 6.18%, were commonly detected by the MJA and CIM. Two M-QTL for seed-stem ratio, qSSR-14 and qSSR-7-2, were commonly detected by the MJA and CIM, where their heritabilities were 13.86% and 6.72%, and their distances across the two approaches were 0.6 and 1.55 cM, respectively.Significant cytoplasmic and environmental effects were evident for all the above traits except for stem diameter and branches number. Meanwhile, QTL-by-cytoplasm and QTL-by-environment interactions were also identified. Some common results were shown, for example, three environmental interactions, qHl-14e-1, qHl-1e and qHI-7e, were consistent with three M-QTL commonly detected by the MJA and CIM, and qSSR-5c was confirmed by qSSR-5 because that they are in the same marker interval and their distance is only 0.4 cM.Finally, twenty-one QTL detected in this study along with ninety complete information QTL for plant height from previous studies of other groups were used to carry out Meta analysis by BioMercator 2.1. Eight clusters of QTL were found in the integrated map. Among these clusters QTL, five QTL(qPH-6-2, qPH-6-3, qPH-7-1, qPH-7-2, qPH-7-3) were included in this study. Eighteen consensus QTL, with 95% confidental intervals of 0.81 to 3.50 cM, were found.