Molecular Tagging And QTL Mapping Of Gene Conferring Resistance To Soybean Cyst Nematode Race 4

Soybean Cyst Nematode (SCN) (Heterodera glycines Ichinohe) is a kind of soilborn sedentary endoparasite nematode and the pathogen of soybean chlorsis. It has more than ten physiological races. It is economically the most destructive pathogen affecting soybean cultures. SCN Race 4 is the predominant race that is the most damaging pathogen in China. Classical genetic studies have demonstrated that resistance to SCN is controlled by 1 to 4 nuclear genes and can be conferred by linked genes that can have more than ten multiple alleles for each resistance locus. The advent of molecular markers and quantitative trait locus (QTL) mapping methods in the last decade gives an efficient alternative to study the mechanism of resistant to SCN. It will be considerable significance in the research of SCN-resistance breeding. A population of 253 F23 families were used for molecular marker identification. This population was generated from a cross between the resistant cv. ZDD23 15 and the releasing cultivar Jindou23 (susceptible to SCN Race4). The ZDD2315, a local germplasm of Shanxi province, has a high resistant to SCN Race4. The F2 population and the corresponding F2 3 families were used to evaluate the correlation between the molecular marker and resistance to SCN Race4 based on the numbers of SCN in soybean root using the method of soybean seedling planting in plastic bags. The objectives of this work were to identify?and map QTLs for resistance to SCN Race4 with the aid of SSR and ISSR markers. The results are summarized as follows: 1. According to the linkage group A and G of soybean molecular genetic map published, twenty SSR markers had been employed in this research. Eight SSR markers (SattO38 (176,182), Satt3O9 (130,135), Satt6lO (240,222), Sattl87 (300,250), Sat 141 (189,184), Satt3lS (253,248), Satt632 (286,290), Satl 62 (200,286)) were identified in the F23 population using the bulked segregant analysis (BSA) technique. These markers are co-dominant, single segregant locus, good repetitive and stabiliable. A hundred of ISSR markers were used to screen resistance to SCN Race4. One ISSR marker (UBC8 11340) has been identified by using BSA technique in the F2.3 populations. The ISSR marker is a dominant marker, and the size of amplifing band is 340bp appearing in the susceptible parent and its F2 lines. In this work, the morphologic agronomic character, black seed coat (BSC), had been investigated in F2 population. The result showed that the genotype of BSC is separated by expected 3:1, which can be predicted by a recessive locus. BSC morphologic marker seems to be quantitative, which is coincident to Mendelian rules. 2. The identified markers mapped to the soybean genetic linkage map have been carried out by using JOINMAP program. Five markers, which are Sat₁41 Satt6lO, SattO38, Satt3O9 and UBC811, were mapped to linkage group G whose length is 50.5cM. Four markers including Satt3 15, Sattl 87, Satt632, Sat₁62 and one morphologic marker (BSC) were mapped to linkage group A whose Length is 53.7cM. 3. Three new QTLs had been mapped to soybean linkage A and G, respectively, conferring resistance to SCN Race4. There is one mapped QTL on linkage group G that maps 2.0cM from Satt6lO marker. It is named rhg-R4g1 that explains 15.87% of the total phenotypic variation. There are of the two QTLs, which map 0.2cM from Sat₁62 marker and 1.6cM from BSC marker on linkage group A, respectively. They are named rhg-R4a1 and rhg-R4a2 th...