2013 Annual Report
Misting systems will be established and managed to create contrasting micro-climates that will be assessed to determine their ability to create conditions favorable for sclerotinia head rot infections and thus the evaluation of sunflower resistance. The contrasting micro-climates will be developed by utilizing different misting timings, misting durations, and mist intensities. The misting systems will be equipped with different emitters, spacing, and risers along with timers to achieve the different environments. Climate and plant canopy sensors tied to data loggers will be used to record the micro-climate variables. A series of known sunflowers hybrids will be planted and inoculated with ascospores in accordance with proven procedures. Assessments of head rot infection will be recorded and compared across the different misting system regimes. The different climatic data that is associated with each misting regime will evaluated to identify those conditions that best promote sclerotinia head rot infections.
Upon project initiation, the breeding for Sclerotinia head rot resistance in sunflower hybrids was in very early stages of development, and it was unknown whether commercial hybrids differed in their susceptibility to Sclerotinia head rot. Over the past several years, the project has documented that significant, repeatable differences exist in the susceptibility of sunflower hybrids to Sclerotinia head rot. The project has assessed the Sclerotinia head rot resistance of new commercial hybrids as those hybrids have been introduced into the market, thereby providing growers with independent data on the Sclerotinia head rot resistance of commercial hybrids. The project has also played a key role in the development of new hybrids with improved Sclerotinia head rot resistance by screening sunflower breeding lines and elite experimental hybrids for their resistance to Sclerotinia head rot. Finally, the project has been successful in developing inoculation procedures and misting systems that reliably lead moderate to high levels of Sclerotinia head rot infection that are needed to identify the relative susceptibility of sunflower hybrids to Sclerotinia head rot. Over the years of this project, both public and private sunflower breeders have been able to effectively screen their hybrids or breeding lines and thereby identify differences in resistance to Sclerotinia head rot. The success of these annual assessments has fostered improvements in the overall resistance to Sclerotinia head rot and the number of hybrids with improved levels of resistance. Sunflower growers now are able to review the results of the field trials associated with the project to identify and select commercial hybrids that have improved resistance to Sclerotinia head rot and stalk rot.
In 2012, field trials associated with this project resulted in (1) the identification of commercial sunflower hybrids and breeding lines with elevated resistance to Sclerotinia head rot, (2) preliminary recommendations for improving the methods used to screen sunflowers for resistance to Sclerotinia head rot, and (3) a preliminary assessment of the prospects of using fungicides to manage this disease.