Журнал патологии растений и микробиологии

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Interactions between Four Fusarium Species in Potato Tubers and Consequences for Fungal Development and Susceptibility Assessment of Five Potato Cultivars under Different Storage Temperature

Boutheina Mejdoub-Trabelsi, Hayfa Jabnoun-Khiareddine and Mejda Daami-Remadi

Fusarium dry rot of potato caused by F. sambucinum, F. oxysporum, F. solani and F. graminearum is particularly prominent in Tunisia resulting in partial or complete tuber decay during storage. This fungal complex can occur within the same potato tuber. Cultivar’s reaction to different mixtures depending on the temperature of storage used can give additional information on their relative aggressiveness. Thus, interactions between these Fusarium species was investigated using single and mixed infection onto five local potato cultivars (Spunta, Oceania, Nicola, Mondial and Atlas) under two temperatures (20 and 30°C). Data indicated that the lesion diameter and the penetration of dry rot, noted 21 days post-inoculation, varied significantly depending on cultivars, inoculation treatments and temperatures of storage tested and their interactions. The combination of F. sambucinum and F. solani (C2-1) was found to be the most aggressive inoculation treatment. This treatment was followed by the association of F. sambucinum with F. oxysporum (C2-4) and the combination of F. sambucinum with F. solani and F. graminearum (C3-4). However, the four Fusarium species, when considered individually, exhibited globally reduced aggressiveness as compared to the tested complexes suggesting occurrence of synergistic interaction. Overall, all mixed inoculums including F. sambucinum showed increased aggressiveness levels on the majority of cultivar x temperatures combinations. Potato cultivars exhibited differential response to the different Fusarium mixtures tested depending on the temperature of storage used. None of the cultivars tested was completely tolerant to all inoculation treatments and only cvs. Spunta and Oceania exhibited lesser susceptibility to four mixtures. The isolation frequency of Fusarium species was also variable depending on single or mixed inoculum used for tuber infection and according to cultivar × temperature combination considered. This relative predominance may reflect their competitive potential in mixture and their relative involvement in dry rot development and severity.