Effect of Single and Combined Inoculations of Potato Plants with Four Fusarium Species on Wilt Severity, Plant Growth, and Production

Abstract

Potato (Solanum tuberosum L.) Fusarium wilt is an increasingly serious disease in many potato-growing regions worldwide and notably in Tunisia. Fusarium sambucinum, F. oxysporum, F. solani, and F. graminearum are the main causal agents with F. oxysporum being the most aggressive on plants. Co-infection with this Fusarium species complex is frequently observed. Cultivar responses to different pathogen mixtures can give additional information on the relative aggressiveness of the different complexes. This study may lead to a better understanding of how interactions between the four Fusarium species may affect disease incidence and severity. Interactions between these Fusarium species was evaluated using single and combined inoculations (15 different Fusraium inocula) onto potato the two cultivars Spunta and Oceania. The tested inocula were evaluated for their effects on leaf yellowing and necrosis, vascular discoloration severity, potato growth and production. Necrosis severity noted 75 days post-planting induced by three different inocula C2-1 (F. sambucinum + F. solani), C2-2 (F. solani + F. oxysporum), and C3-3 (F. sambuinum+F. oxysporum +F. graminearum) were found to be the highly aggressive inoculation treatments. Overall, all mixed inocula including F. sambucinum showed increased aggressiveness levels. The two cultivars exhibited differential response to the different tested Fusarium mixtures and behaved in the majority as sensitive to moderately sensitive to C1-1, C1- 4, C2-1, C2-2, C2-3, C2-4, C2-5, C2-6, C3-1, C3-3, C3-4 and C4 treatments. This study clearly demonstrated that Fusarium wilt of potato is expected to be more severe when more than one Fusarium species is present. The relative predominance of F. sambucinum may reflect its competitive potential in mixture and its significant involvement in potato Fusarium wilt severity.