2013 Annual Report
1a.Objectives (from AD-416):
The goal of this project is threefold: (1) to find new sources of Sclerotinia head rot resistance in cultivated sunflower germplasm, (2) to improve existing methods of ascospore production and assess them across multiple laboratories, and.
3)to transfer Sclerotinia stalk and head to resistance by conventional breeding and marker-assisted selection (MAS) into elite USDA sunflower germplasm for release to the public. Specifically, the project will (1) evaluate new cultivated sunflower accessions of the USDA Plant Introduction Station’s seed collection for resistance to head rot; (2) use the phenotype data for head rot and stalk rot in association mapping; (3) test modifications of ascospore production using the method developed by Dr. M. Boosalis, at multiple laboratories; and (4) cross new sources of Sclerotinia resistance into elite oilseed and confection USDA germplasm.
1b.Approach (from AD-416):
To increase the genetic diversity of Sclerotinia resistance within the USDA breeding program, we will evaluate both the newest USDA Plant Introductions (which have not been tested for disease resistance) and seek new germplasm via exchanges with foreign public breeding programs. The evaluations will be done with artificial inoculations at multiple test sites in North Dakota and Minnesota. Once new sources of stalk rot and head rot resistance are identified, we will determine with the aid of MAS whether these contain new genes. Once resistance sources are identified, they will be crossed into either elite oilseed or confection lines. Dr. M. Boosalis, retired Plant Pathology chairman at U. Nebraska, has been producing Sclerotinia ascospores for 25+ years with a proprietary, unpublished protocol. We will work with him to test his method with several Sclerotinia isolates at four laboratories to assess the method’s general applicability.
In 2012, we had two inoculated stalk rot nurseries (Carrington, ND and Crookston, MN) and two inoculated, misted head rot nurseries (Staples and Sabin, MN), in which we evaluated a total of 4,600 rows of sunflower germplasm. Phenotyping of 250 USDA cultivated sunflower Plant Introductions (PIs) for head rot was completed, yielding four datasets over two years, which complemented the six datasets of stalk rot data and four datasets of Phomopsis stem canker data gathered previously, all of which will be used in association mapping. From this multi-year head rot analysis, we identified 25 accesions with an average of < 16% nfection, compared to the HA 89 check at 76% infection, and the mean across all entries of 61% head rot. Seven of the ten most resistant accessions (0 to 6% infection) were old Hungarian land races. In addition to testing of the USDA PIs, we evaluated USDA breeding lines from four USDA scientists for head rot and stalk rot that were in various stages of selection. Several germplasm releases with improved head rot resistance are planned for 2013. Other work completed during 2012 was a multi-lab study whose objective was to document and potentially modify the very successful ascospore production method developed by retired U. Nebraska pathologist Mike Boosalis. The method developed by M. Boosalis was tested on five genetically diverse isolates of Sclerotinia sclerotiorum in four laboratories (Lincoln and Scottsbluff, NE, and Carrington and Fargo, ND). Two of the four labs had problems producing apothecia and ascospores, illustrating how tricky large-scale ascospore production can be. In the remaining labs, the method developed by M. Boosalis was effective at generating ascospores from two of the five isolates, including the isolate that M. Boosalis used to develop his method. For the remaining isolates, few if any apothecia and ascospores were produced. Slight modifications to the method did not change this outcome. The results suggest that this method is very useful for generating ascospores from specific isolates of S. sclerotiorum, but will not be useful for all isolates. Further work is planned for 2013 in which other media components will be examined and well as sterilization procedures to minimize contamination, a minor but essential consideration.