Sprout-suppressing 1,4-dimethylnaphthalene treatment reduces dry rot infection in potato tubers during postharvest storage

Postharvest losses related to dry rot can reach 60% during long-term storage of potato tubers. Current control methods do not provide an efficient solution to control dry rot, and inducing resistance through elicitors may be a promising way to manage this disease. In this study, we evaluated the ability of 1,4-dimethylnaphthalene (1,4DMN) and methyl jasmonate (MeJa) to induce resistance to dry rot caused by Fusarium nirenbergiae, using 'Asterix' and 'Challenger' under refrigerated storage conditions. In vitro and in vivo tests were performed evaluating the volume of infection and the activity of antioxidant and defense enzymes, including polyphenol oxidase, peroxidase, catalase, ascorbate peroxidase, phenylalanine ammonia lyase, lipoxygenase and beta-1,3 glucanase. The results reinforce the difference in susceptibility to dry rot between the genotypes, with the 'Asterix' and 'Challenger' being classified as resistant and susceptible, respectively. The in vivo tests corroborated the findings of the in vitro tests, demonstrating that only 1,4-DMN retarded the growth of F. nirenbergiae. Throughout the progression of the disease, the activity of the defense enzymes revealed a more consistent response regarding the difference in susceptibility between cultivars than in response to the applied elicitors. Therefore, our data suggest that the efficiency of 1,4-DMN in reducing the volume of infection is linked to its direct action on the pathogen and not to the activation of a defense switch via antioxidants and defense-related enzymes. Unlike 1,4-DMN, MeJa did not control potato dry rot.