Bio-suppression of Fusarium Wilt Disease in Potato Using Nonpathogenic Potato-associated Fungi

Ten nonpathogenic Aspergillus spp. and Penicillium spp. isolates, naturally occurring within healthy potato plants and previously selected based on their ability to suppress Fusarium dry rot disease, were evaluated for their in vitro antifungal potential against Fusarium sambucinum, F. oxysporum and F. graminearum and their effects against Fusarium wilt severity and on plant growth and production. Tested through the dual culture technique on PDA medium, all isolates tested had significantly decreased Fusarium spp. growth relative to the untreated control. Growth inhibition, achieved after 7 days of incubation at 25°C, varied from 32.3 to 42.9% using Aspergillus spp. and from 44.1 to 59.6% with Penicillium spp. The highest inhibition, by about 55-59%, was noted using isolates E.36.11 (P. chrysogenum) and E.39.11 (Penicillium sp.). Competition, mycoparasitism, hyphal lysis, early formation of resting structures and mycelial cords, and decreased sporulating ability are the main effects recorded during antagonism exerted toward targeted Fusarium species. Fusarium wilt severity, noted 75 days posy-planting, was significantly lowered by 29 to 47% on potato plants treated using 7 out the 10 isolates tested. The highest wilt severity decrease, by 41-47% over the inoculated and untreated control, was achieved using E.13.11 (A. niger), E.25.11 (A. flavus), E.36.11 (P. chrysogenum), and E.29.11 (P. polonicum) based treatments. Plant inoculated with Fusarium spp. and treated with E.29.11 (P. polonicum), E.13.11 (A. niger), E.41.11 (A. terreus), E.60.11 (A. flavus), and E.25.11 (A. flavus) showed 36-46% higher aerial part growth. The most interesting improvements of root and tuber fresh weights, achieved using the majority of isolates tested, ranged between 22-40% and 15-21%, respectively. Further investigations are needed to more elucidate the antifungal activity of the extracellular metabolites of the most effective isolates toward Fusarium species infecting potato.