Effects of tillage and organic fertilization on potato tuber dry rot under Mediterranean conditions

Dry rot of potato caused by Fusarium spp. affects tubers in the field and during storage and represents the primary postharvest loss. The present study aimed to assess, in a two-year trial (2021-2022) conducted in Central Italy, the effects of a sustainable and circular cultural model consisting of two conservative tillage techniques (subsoiling and spading) versus ploughing and organic fertilization by compost versus mineral fertiliser on the severity of tuber dry rot and fungal species involved. A high percentage of dry-rotted tubers was recorded in the cropping season 2022, characterized by abnormally high temperatures. In 2022, spading combined with compost fertilization led to a significant decrease in dry rot. Fusarium brachygibbosum was the predominant and most virulent pathogen isolated from symptomatic tubers, followed by F. oxysporum and F. equiseti. Fertilization with compost, particularly when combined with subsoiling, significantlu decreased the frequency of F. brachygibbosum. On symptomatic tubers, the antagonists and hyperparasites Trichoderma atroviride and T. gamsii were also isolated, more frequently on tubers from organically fertilized plots. The saprophytic and antagonistic fungus Linnemannia elongata was isolated on tubers from subsoiling. Plants grown on soil fertilized with compost significantly increased colonization by the arbuscular mycorrhizal fungus identified as Paraglomus occultum. Sustainable and circular agriculture management systems can maintain or restore soil fertility through conservative tillering and organic fertilization and minimizing losses due to diseases such as dry rot of potato tubers.