Reference Report for RGB20110815.4
| Title: | Genetic analysis infers Dt loci resistance to Fusarium solani f. sp. Glycines in indeterminate soybeans |
| Authors: | Njiti, V., Lightfoot, D. |
| Source: | Can. J. Plant Sci. 2006, 86(1):83-90 |
| Abstract: | Improved resistant cultivars are being developed to better withstand the sudden death syndrome (SDS) of soybean (Glycine max L. Merr.) caused by Fusarium solani (Mart.) Sacc. f. sp. glycines (Fsg) (renamed F. virguliforme). Field trials to identify and select SDS-resistant cultivars take several years and are expensive. Selection of seedlings in the greenhouse and marker assisted selection are faster and cheaper. Selection for loci contributing SDS is well established for southern US germplasm sources (Forrest, Pyramid) but untested in northern germplasm. The aim was to find DNA markers associated with loci contributing seedling resistance to F. solani in the northern germplasm cultivars Minsoy and Noir. The greenhouse assay used plants grown for 3 wk in F.solani inoculated soil. Disease severity (DS) was recorded for 2000 recombinant inbred lines (RIL) from Minsoy _ Noir1 (M_N) after F. solani infestation and compared to the DS of non-infested controls. Minsoy was partially resistant and Noir1 was relatively susceptible to F. solani. The heritability of DS was 48%. Comparison of alleles at 247 loci with the DS trait identified three regions associated with DS. Two regions within a 16 cM region of linkage group L (U14) were identified by markers SAT99 (P = 0.0006, R2 = 7%) and SATT6 (P = 0.0013, R2 = 5%). One region on linkage group C1 (U10b_ was identified by A063_1 (P = 0.0011, R2 = 5%). Interacting loci explained an additional 12% (A280 and SAT99) and 10% (R28 and SATT6) of the variability in DS, mainly by increasing resistance in susceptible class at each quantitative trait loci (QTL). These loci jointly explain the major portion (34%) of heritable resistance to F.solani. The QTL did not correspond with the known loci that condition resistance in the field in southern US germplasm. The QTL were in regions of the genome that were previously determined to alter determinacy, plant morphology, leaf shape, stem thickness, plant height, maturity and water use. Here Minsoy was taller, had thicker stems, produced more root mass and more shoot mass than Noir 1 during Fsg infestati on. Height (r = 0.15, P = 0.03), root weight (r = 0.3, P = 0.0002) and shoot weight r = 0.4, P = 0.0001) were significantly negatively correlated with resistance to SDS. Therefore, we conclude the SDS resistance is a pleiotropic effect of shoot and root characters in Minsoy and Noir that may confound selection for resistance to SDS in North American germplasm. |
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