1a.Objectives (from AD-416):
The long-term goal of this project is to develop soybean varieties or germplasm that have a high level of resistance to Sclerotinia stem rot. The short-term supporting objectives are: (1) further evaluate the advanced lines selected from a previous project and release the best lines as germplasm or varieties; (2) evaluate seven populations of F4 derived lines with resistance from five new resistant plant introductions (PIs) for resistance to Sclerotinia stem rot and agronomic traits; and (3) determine if reported QTLs associated with resistance to Sclerotinia stem rot are also associated with the resistance in the five new resistance sources.
1b.Approach (from AD-416):
For objectives 1 and 2, the lines will be evaluated in multiple locations in Michigan for yield and agronomic traits. The lines will also be evaluated for resistance to Sclerotinia stem rot in the greenhouse with the spray-mycelium method and/or drop-mycelium method developed by us. About 15% of the lines will be selected based on the greenhouse resistance to Sclerotinia stem rot, yield, and other agronomic traits. The selected lines will be evaluated in our disease nursery for resistance to Sclerotinia stem rot and yield under disease pressure. Five to 10 lines will be selected and tested in the Uniform Soybean Tests – Northern Region (19 locations in 10 northern US states and 1 Canadian province), for yield and other agronomic traits. The best 1-3 lines will be released to the public. For objective 3, the same seven populations evaluated for objective 2 will be genotyped with polymorphic SSR (simple sequence repeat) and SNP (single nucleotide polymorphism) DNA markers within 20 cM on either side of 34 reported QTLs for resistance to Sclerotinia stem rot. The DNA marker data and the disease resistance data obtained under objective 2 will be analyzed together to determine if the reported QTLs are also associated with the resistance in the five new resistance sources.
This project was initiated on June 1, 2009, research is ongoing, and the overall goal of this project is to develop soybean varieties or germplasm that have a high level of resistance to Sclerotinia stem rot.
We evaluated 995 elite soybean cultivars for resistance to Sclerotinia sclerotiorum in the greenhouse using our drop-mycelium method. These 995 cultivars were also genotyped with 52,041 SNP markers. A genome wide association analysis was conducted with the disease resistance data and the SNP marker data of the 995 cultivars. The analysis revealed significant associations between SNP markers and the resistance to the disease at 9 loci, including 4 that were not reported in the literature. The SNPs at the identified loci explained 38% of the phenotypic variance. The identification of such associations will provide significant insight into soybean resistance to Sclerotinia sclerotiorum and will also facilitate marker-assisted selection for resistance to the disease in soybean.