Submitted to: American Phytopathology Society
Publication Type: Abstract Only
Publication Acceptance Date: December 11, 2008
Publication Date: January 30, 2009
Citation: Mengistu, A., Reddy, K.N., Zablotowicz, R.M. 2009. Propagule Densities of Macrophomina phaseolina in Soybean Tissue and Soil Under Mississippi Conservation Management System. American Phytopathology Society. doi:10.1094/PHP-2009-0130-01RS Technical Abstract: Field experiments were conducted in 2002 through 2004 at Stoneville, MS, to determine the population dynamics (colony forming units [CFU]) of Macrophomina phaseolina (Tassi) Gord in glyphosate-resistant soybean [Glycine max (L.) Merr.] stem and root tissues, and in soil at planting and at harvest as affected by tillage [(conventional tillage (CT) and no-tillage (NT)], cover crop (CC) (hairy vetch, rye , and no cover crop) and herbicide (glyphosate and non-glyphosate). Propagules of M. phaseolina ranged from over 200 to greater than 11,000 colony forming units (CFU) g-1 of tissue, but soil propagules ranged from none detected to 200 CFU g-1 soil. There was a significant effect of year, tillage and CC and the interactions of year by tillage and year by CC on propagules of M. phaseolina from soybean tissue, with higher CFU associated with soybean from CT soils in 2002, and higher CFU associated with hairy vetch compared to rye or no cover crop. Analysis of the main effects indicate that CFU recovered from stem and root tissues were significantly higher in 2002 than in 2003 or 2004. Soil CFUs were generally two-fold greater in soil sampled at harvest compared to planting, indicating greater inoculum increase during the season. The data from this study suggests that disease incidence may be greater under CT than NT soils and that hairy vetch is a susceptible host for M. phaseolina or promoted soil conditions for its proliferation. In addition, estimating occurrence of propagules density in soybean stem and root tissues is a more reliable indicator for predicting inoculum potential than using propagules in soil.