1a. Objectives (from AD-416):
Obj 1. Determine soybean yield loss associated with infection by Macrophomina phaseolina and charcoal rot development in the North Central U.S. Obj 2. Assess seasonal progress of charcoal rot (pathogen colonization and disease development) in the North Central U.S. Obj 3. Evaluate high-yielding commercial soybean varieties adapted to the North Central U.S. for field resistance to charcoal rot.
1b. Approach (from AD-416):
Obj 1 and 2. Four commercial soybean varieties (maturity group-MG 2.0-2.5) will be planted on 1-2 research farms in IN, WI, and MI. Treatments will be irrigated/infested, irrigated/non-infested, non-irrigated/infested, and nonirrigated/non-infested and arranged in a split-randomized complete block design with irrigation being the main plot. Soil populations (colony forming units-CFUs) of M. phaseolina will be assessed post-planting and pre-harvest. Disease development and colonization by M. phaseolina (plant CFUs) will be assessed at soybean growth stages VC, V5, R2, R4, R6, and R8. Yield will be assessed at maturity. Obj 1. Commercial farms in OH with a history of charcoal rot will be grid-sampled for soil CFUs of M. phaseolina to determine areas of high and low disease pressure. A commercial variety will be grown and yield and plant CFUs assessed at maturity. Comparisons will be made between plants grown in high disease pressure areas versus low. Obj 3. Twenty commercial soybean varieties will be planted on 2 research farms in IN (MG 2.5-3.5), WI (1.0-2.0), and MI (2.0-2.5). Plots will be irrigated or non-irrigated and all will be artificially infested with M. phaseolina. Soil CFUs will be determined postplant and pre-harvest and disease developed at stages VC, V5, R2, R4, R6, and R7. At maturity, varieties will be assessed for yield and plant CFUs.
3. Progress Report:
Objectives 1 and 2. Four commercial soybean varieties in maturity groups (MG) I-III, two resistant and two susceptible to charcoal rot based on greenhouse evaluations, were planted in field locations in Indiana, Wisconsin, and Michigan, between 6 May and 18 June 2013, in collaboration with scientists at Purdue University, University of Wisconsin-Madison, and Michigan State University. Soil samples were collected from non-infested plots 7-14 days after planting to determine the amount of Macrophomina phaseolina, the causal agent of charcoal rot, naturally occurring in the various field locations. Soil populations based on colony forming units (CFUs) were negligible at each location. Plant samples (main tap root and hypocotyl) were collected at soybean growth stages VC, R1, and R3 from each location and are being processed to determine the amount of M. phaseolina present based on CFUs. Samples at V5 were collected only from locations in Michigan. Additional samples will be obtained from each location at growth stages R5 and R7, and yield will be determined at harvest. Samples collected at VC were positive for M. phaseolina indicating infection occurs early in the growing season. Objective 3. Ten commercial soybean varieties in MG I, II, and III (30 total) were obtained from a commercial soybean company and planted in field locations in Wisconsin (MG I), Michigan (MG I, II, and III), Iowa (MG II), and Indiana (MG III) between 6 May and 18 June 2013 in collaboration with scientists at Purdue University, Michigan State University, University of Wisconsin-Madison, and Iowa State University. Plant samples (main tap root and hypocotyl) were collected at soybean growth stages VC, R1, and R3 from each location and are being processed to determine the amount of M. phaseolina present based on CFUs. Additional samples will be obtained at growth stages R5 and R7, and yield will be determined at harvest.