Construction Of Soybean Genetic Map By SSR And Its Application In Mapping Of Soybean Disease-Resistance And Insect-Disease Genes

Soybean is originated from China. The planting history of soybean is very long, butthe anti-virus and anti-insects history of soybean is as long as well. Soybean Mosaic Virusdisease and soybean defoliating insects are two of the most serious factors that damage thesoybean production. Soybean mosaic virus disease was caused by soybean mosaic virus(SMV), one of the most destructive viruses that infect soybean. SMV spread widely in thesoybean production regions and seriously affects the soybean production and quality. InChina, defoliating insects also have a very wide distribution and cause huge lost as well.However, so far, most of the commercial soybean cultivars planted in China is neither SMVnor defoliating insects resisted. Therefore, it is important to carry out the researches on thegenetic analysis of soybean germplasms, mapping of new resistance genes and breeding ofnew resistance soybean cultivars by Marker Assisted Selection (MAS) method.In this study, the RIL population, NJRIKY, used was derived from the cross KefengNo.1 xNannong 1138-2 by single-seed-descent (SSD) and multiple-seed-descent (MSD)procedures. The original population consisted of 206 F_2:7:8 lines and was later adjusted to184 lines using simulated population criteria (SPSC) method. The RIL population we usedhere consisted of 184 F_7:11 lines. Molecular markers were used in evaluating the population.PCR markers-based genetic maps of this population were constructed. The inheritance ofresistance to the SMV predominant strains and mapping of resistance gene were studied.The inheritance of resistance to cotton worm was also estimated and the mapping ofsoybean insect resistance QTLs was studied by using the RIL population, NJRIKY. Themain results are given as follows:1. 822 pairs of SSR primers, which cover the whole soybean genome, one pairs ofSCAR primer and eight pairs of primers designed from soybean ESTs respectively, wereused to evaluate the 184 lines of RIL population, NJRIKY,. This RIL population originallyconsisted of 201 F₁₁ lines and was later adjusted to 184 lines using the Simulated Population Sampling Criterion method.Evaluation showed that almost all the marker loci and lines were purified. The contentof Kefeng No.1 and Nannong 1138-2 contributed to the 184 lines population was about0.507 and 0.493, respectively. The distribution of genotypic composition of the populationfitted well. Genetic distances of each pair of lines were calculated by Nei's method. Theresults of cluster by method UPGMA showed that the population had less over presentation.In a word, the population was suit to genetic mapping and other genetic research for itswell-dispersed genetic structure.2. A genetic map based on PCR markers was constructed with this population. Itcovered 25 linkage groups and contained 276 loci including 271 SSR markers, one SCARmarker, one CAPS marker, two classical markers and one resistance gene. The length of themap was 3179.8 cM and the average distance of loci was 11.5 cM. It was easy to comparethis map to soybean integrated genetic map for most markers in this map were SSRs and itfitted the integrated genetic map well both in the sequences and the distances of markers.Two traits, soybean black seed color and soybean flower color, were located on linkagegroup G2-A2 with distance of 1.2cM away from Sat₁62 marker and on linkage groupG11-F with distance of 7.7cM away from AW186493 marker, respectively.3. In this study, segregation ratios of resistant plants to susceptible plants in P₁, P₂, F₁,F₂ populations of Zhongdou No. 5 (susceptible)×Pixianchadou (resistant) were used tostudy the inheritance of resistance to the SMV strain SC-8. Populations Pixianchadou andF₁ were found to be completely resistant to this SMV strain while Zhongdou No. 5 wassusceptible to it. The F₂ populations segregated to fit a ratio of 3:1 for resistant plants tosusceptible ones. These results indicated that a single dominant gene controlled resistanceto the SMV strain SC-8 in Pixianchadou. P₁, P₂, F₁, F₂ populations of Kefeng No. 1 (P₁)×Nannong 1138-2 (P₂) and derived RIL populations, were used to study the inheritance ofresistance to the SMV strains SC-3 and SC-7. Results indicated that two genes and a singledominant gene controlled resistance to the SMV strains SC-3 and SC-7 in Kefeng No.1,respectively. Molecular markers were used to analyze the RIL population andMAPMAKER/EXP 3.0b was employed to establish linkage between markers and resistancegene. Combining the data of markers and resistance identification, the resistance gene,designated as Rsc-7, which controlled resistance to the SMV strain SC-7 was mapped to themolecular linkage group G8-D1b+W. Five SSR markers Satt266, Satt634, Satt558, Satt157,and Satt698 were found linked to the resistance gene Rsc-7. 4. The RIL population, NJRIKY, was employed as experimental materials. Larvalweight and pupae weight of cotton worm [Prodenia litura (L.) Fabricius] were examinedand used as index of resistance. The inheritance of resistance of soybean to cotton wormwas estimated by using major gene plus polygene mixed model. It was shown that theinheritance of resistance to cotton worm was controlled by two major genes plus polygenewhile using either larval weight or pupae weight as index of resistance, with the heritabilityof 66.48% and 67.96%, respectively.Based on the linkage map constructed with molecular markers of the RIL population,NJRIKY, and the QTL Cartographer software V2.5, one QTL related to the larval weighttrait was mapped on linkage group G20-O and the position was 31.91 cM. This QTL'sadditive effect was 0.0408 and explained 11.74% of the total variation of larval weight.Two QTLs related to the pupae weight trait were mapped on linkage group G8-D1b+Wand G17-L and the positions were 14.71cM and 0.01cM, respectively. The QTLs' additiveeffects were -0.0139 and 0.0103 respectively and explained 11.30% and 6.36% of thetotal variation of larval weight, respectively.