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Dynamics of microbial communities associated with broccoli residue and chitin amendments on suppression of Verticillium wilt in three soil types

Krishna Puri: University of California, Davis

<div>The potential for soil amendments to stimulate and promote disease suppressive microbiomes antagonistic to <em>Verticillium</em> spp. were evaluated in three soil types. Broccoli residue (10% w/w), chitin-based crab meal (0.2% w/w), and a combination treatment were applied to three soils with distinct land use histories: intense agriculture, transition from pasture to agriculture, and native, undisturbed soil. In greenhouse experiments, prokaryote, fungal and oomycete communities; disease severity (DS) on <em>Solanum melongena</em> (eggplant); microsclerotia (MS) density in soil; chitinase activity; and soil physicochemical properties were monitored and analyzed over time. Preliminary prokaryote community analyses indicated that broccoli and crab meal amended soil enriched known fungal antagonists such as <em>Sporocytophaga</em>, <em>Streptomyces</em>, <em>Pseudomonas</em>, <em>Bacillus</em>, and <em>Nannocystis</em>. The same treatments enhanced Bacteroidetes in agricultural and non-agricultural soil but decreased them in transition soil. The DS and MS density significantly decreased over time relative to the unamended control. A detailed analysis of temporal microbial dynamics, and correlations between disease suppressiveness, enzyme activity, MS counts, and soil properties are ongoing. The results indicate that broccoli alone or in combination with crab meal reduces Verticillium wilt severity and enhances suppression-associated microbes, and thus may represent a cultural approach to wilt management in the absence of soil fumigants.</div>

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