1a.Objectives (from AD-416)
To idenify new sources of charcoal resistance in adapted and exotic germplasm.
1b.Approach (from AD-416)
A uniform cultivar screening protocol will be developed and implemented. A set of standard susceptible cultivars will be used. These standard susceptible cultivars will represent early and late cultivars with in maturity groups 3 through 5. Tests will be established in naturally infested fields supplemented with adding inoculum at planting. Disease will be evaluated by rating the development of foliar symptoms of charcoal rot, rate of premature plant death, and by splitting the stems at harvest, visually determining the extent of stem colonization and quantifying colonization by determining the colony forming unit of M. phaseolina. Yields will be taken. Test cultivars will be selected based on previous observations and from other charcoal rot screening tests in the field and in greenhouse and laboratory assays. Soil temperature and moisture and rainfall data will be taken and related to disease development.
The purpose of this project is to screen soybean varieties and breeding lines for charcoal rot resistance across locations in five separate states: Portageville, MO; Rohwer, AK; Carbondale, IL; Jackson, TN; and Parson, KS. The test was initiated in 2008 and included standard susceptible cultivars from maturity groups III-V. Five of the 17 entries in this project are from the soybean lines identified by the USDA, Jackson, TN. Initial two year analysis based on the split stem assay has been completed. DT-9917554, DT-98-7553, and DT-97-4290, previously identified by the ARS Scientist in Jackson were among the lowest in root and stem severity ratings across all locations and the susceptible lines LS98-2574 and Croton were among the highest rated susceptible lines. These results suggest that performance of these lines across the different enviroments is very consistent. New sources of charcoal rot resistance in adapted and exotic soybean germplasm were also being evaluated in the field. In, 2009, 248 exotic PI's from a drought-orine region of China and an additional 296 drought and flood tolerance lines were planted in hill plots in the field for charcoal rot evaluation. Few lines have been identified as having charcoal resistance using the split stem assay, and lines identified as resistant will be retained for further testing the following year. ADODR used site visits to monitor the activities of the project.