Random T-DNA mutagenesis reveals gene candidates modulating pathogen virulence in postharvest Penicillium-apple fruit interactions
Wayne Jurick II: USDA-ARS Food Quality Laboratory
<div>Postharvest blue mold decay of apple fruit is mainly caused by the fungus, <em>Penicillium expansum. </em>Problems with controlling this disease are exacerbated by a limited number of fungicides, no known resistance in apple, and emergence of fungicide resistant strains. Sustainable strategies are needed to control blue mold to maintain fruit quality, reduce economic losses for producers, and eliminate patulin contamination. A forward genetics approach was implemented, using <em>Agrobacterium tumefaciens</em>-mediated transformation, to generate a <em>P. expansum </em>mutant library. A total of ~450 transformants were screened <em>in vivo</em> for defects in virulence on apple fruit. Phenotypes ranged from wild type to completely non-pathogenic and were conducted in two different apple varieties. Strains that were reduced in virulence during apple decay and did not differ greatly from wild type growth in culture on were further analyzed. Specific mutants were characterized to determine T-DNA copy number, location of integration, and the nature of the insertion using molecular tools. Our analysis revealed the identities of several new genes, some with uncharacterized domains/function, that are associated with virulence defects during apple fruit decay. Future studies will utilize well characterized T-DNA mutant strains for omics-based approaches to ascertain the molecular mechanisms of <em>Penicillium </em>virulence with the end goal of translating our findings into practical blue mold controls.</div>
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