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Inhibition of Colletotrichum coccodes and Verticillium dahliae by the Biocontrol Agent Penicillium oxalicum in Potato.

Daniel Farber: Washington State University

<div><em>Verticillium dahliae </em>(<em>Vd</em>)<em> and Colletotrichum coccodes </em>(<em>Cc</em>) are soil-borne pathogens with potential interactive effects, which cause two economically important diseases of potato, Verticillium wilt and black dot, respectively. Both reduce yield and tuber quality. Soil-borne pathogens are difficult to manage by cultural practices, leading to over-use of fungicides. Alternatively, <em>Penicillium oxalicum </em>(<em>Pox</em>) is a biocontrol agent used in integrated pest management (IPM), which has inhibited <em>Vd </em>populations on tomato. To investigate inhibition of <em>Vd </em>and <em>Cc </em>populations on potato, <em>Pox </em>at 3.95 g of infested corn kernels per liter of soil was co-inoculated with either 3.95 g <em>Cc- </em>or <em>Vd-</em>infested sand per liter of potting mix. Positive controls containing <em>Cc </em>or <em>Vd</em> without <em>Pox</em> were also included<em>.</em> Potatoes co-inoculated with <em>Cc </em>and <em>Pox </em>produced significantly fewer microsclerotia than with <em>Cc </em>alone, with means of 1110.4/g and 3109.2/g ground potato stem tissue, respectively (<em>p</em> = 0.018)<em>. </em>However, no significant differences were found in <em>Vd </em>microsclerotia counts, tuber weight or disease severity within stem cross-sections between plants co-inoculated with <em>Pox </em>and <em>Vd </em>or<em> Cc </em>when compared to the positive controls. Results suggest that while <em>Pox </em>may reduce <em>Cc </em>and <em>Vd </em>populations under greenhouse conditions, field trials, as well as examining the efficacy of <em>Pox </em>at higher concentrations, are needed to validate the IPM use of <em>Pox</em> as an effective biocontrol agent to manage these diseases.</div>