POSTHARVEST SUPPRESSION OF POTATO DRY ROT (FUSARIUM-SAMBUCINUM) IN PRENUCLEAR MINITUBERS BY ARBUSCULAR MYCORRHIZAL FUNGAL INOCULUM

Arbuscular mycorrhizae (AM) have been shown to increase plant resistan ce to root-rotting pathogens. This study was conducted to determine wh ether a commercial peat-based medium containing the AM fungus Glomus i ntraradix (Schenck & Smith) could influence postharvest progression of tuber dry rot in prenuclear minitubers of potato (Solanum tuberosum). Minitubers grown in this medium had significantly less tuber dry rot (20-90% reduction) when later inoculated with the dry rot fungus Fusar ium sambucinum relative to minitubers grown in an identical pear-based medium without the AM fungus. This disease suppression was also demon strated in a high-input commercial greenhouse, and occurred despite on ly trace levels of AM colonization of the parent plants, and with no e vidence of enhanced plant phosphorus nutrition or differences in minit uber mineral content. These results suggest that the AM fungal inoculu m has potential for use in suppression of tuber dry rot of potato.