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 resistance to root-rotting pathogens. This study was conducted to determine whether a commercial peat-based medium containing the AM fungusGlomus intraradix (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 fungusFusarium sambucinum relative to minitubers grown in an identical peat-based medium without the AM fungus. This disease suppression was also demonstrated in a high-input commercial greenhouse, and occurred despite only trace levels of AM colonization of the parent plants, and with no evidence of enhanced plant phosphorus nutrition or differences in minituber mineral content. These results suggest that the AM fungal inoculum has potential for use in suppression of tuber dry rot of potato.