| Soybean is an important oil crop with high protein or high oil content and can be used for food and forage around the world. Mapping the QTLs affecting soybean yield, then using modern molecular breeding technology to improve the traits relating to yield is one of the important ways to increase soybean production for meeting the human demand. In this study, a F——6 RIL population containing 261 lines was derived from the cross between cultivar Zhonghuang 13 and lines Zhongpin 03-5373. Zhonghuang 13 has elite traits such as semi-dwarf, wide adaptability, high yield and high-protein and Zhongpin 03-5373 has the characters of high resistance to drought and soybean cyst nematode (SCN). A genetic linkage map was constructed using 172 molecular markers, then QTLs of plant height, 100-seed weight and the resistance of soybean cyst nematode were detected by two mapping methods, composite interval mapping(CIM) and the mixed composite interval mapping (MCIM), which were used to detect the QTLs based on the agronomic traits data from several years and regions .The main results were as follows:(1)124 new molecular markers were developed and 24 of them showing polymorphism between the parents can be used to construct genetic linkage map.(2) A genetic linkage map which included 45 linkage groups has been constructed using 152 SSR markers, 17 InDel markers and 3 EST-SSR markers. The total length of the map was 1499.7 cM and the length of differernt linkage group from 2.2cM to 120.9cM. Number of markers on different linkage groups varied from 2 to 12 and their average distance between neighbor loci was 11.8 cM. These results will set a basis for mapping QTLs.(3)The data of plant height from 6 regions of 4 generations in 2 years were used to detect QTLs and 12 QTLs were found being mapped on D1a, D2, F, G, H, I and L linkage groups. The genetic contribution rate of these QTLs varied from 2.3% to 40.5%. One QTL in markers interval of satt490-satt657 in F linkage group was detected and its genetic contribution rate varied from 25.5% to 40.5% in different environment. The QTL has significant interaction with environment and the heritability of additive by environment interaction effects was 1.2%-2.6%. Another QTL in L linkage group in the markers interval of satt229-satt448 has no significant interaction with environment and its genetic contribution rate varied from 9.5% to 17.1% in different environment. Both of the QTLs on F and L linkage groups were detected in all environments, so we speculated that the two QTLs were main effect QTLs which suffered little environmental impact and can show stable heredity.(4)The data of 100-seed weight from 5 regions of 4 generations in 2 years were used to detect QTLs and we found 9 QTLs being mapped on B1, D2, G, H, L and M linkage groups. The genetic contribution rate of these QTLs varied from 3.2% to 13.7%. One QTL in markers interval of satt561-satt448 in L linkage group was detected in F6-F9 generations and its genetic contribution rate of varied from 6.3%-13.5%. The QTL has no significant interaction with environment, so we think it is a QTL which do not suffer environmental impact.(5)We detected the QTLs of the resistance to soybean cyst nematode race 4 and race 14 and found 3 QTLs in all. These three QTLs were mapped on D2, F and G linkage groups and there genetic contribution rate varied from 7.1% to 14.2%. QTLs on G linkage group resisted both race 4 and race 14 of soybean cyst nematode.In this study, the genetic linkage map we constructed will set a basis for mapping important agronomic traits and the QTLs of 100-seed weight, plant height and resist to SCN we have found will provide theoretical basis and guidance for increasing the density of genetic map, separating sub-populations, fine mapping the target genes and molecular assisted breeding in soybean. |
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