Melatonin effects on potato yield and disease resistance assessed through exogenous application and endogenous modification

Authors: Jones, Richard

Submitted to: Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/7/2025
Publication Date: 4/29/2025
Citation: Jones, R.W. 2025. Melatonin effects on potato yield and disease resistance assessed through exogenous application and endogenous modification. Potato Research. https://doi.org/10.1007/s11540-025-09864-y.
DOI: https://doi.org/10.1007/s11540-025-09864-y

Interpretive Summary: Phytomelatonin is produced by a wide range of plants where its function has only recently been investigated. Studies suggest it may have multiple activities that can benefit stress reduction in plants subjected to disease or unfavorable environmental conditions. Potato is a major food crop that would benefit from natural products that alleviate the impacts of disease causing microbes. Melatonin applications to potato plants did not alter disease susceptibility in greenhouse studies, but did increase total tuber weights. Modifying production of melatonin in potato plants was tested by targeting two genes in the biosynthetic pathway. Increased levels of gene expression caused plants to grow short, thick stems and leaves along with small, distorted tubers, indicating that the genes would be undesirable for modification of melatonin levels. This information will be useful to scientists as they further assess the potential benefits of exogenous and endogenous manipulation of melatonin in potato plants.

Technical Abstract: Interest in phytomelatonin biosynthesis and activity has increased due to apparent effects on enhancing resistance to biotic and abiotic stress. Activity related to biotic stress has been associated with increased salicylic acid production and interaction of melatonin with reactive oxygen radicals. Activity related to abiotic stress is associated with alterations in auxin responses, providing reduced levels of senescence. The role of melatonin was investigated in potato using weekly exogenous application of a 2mM melatonin sprayed onto leaves of whole plants. Modification of endogenous melatonin biosynthesis involved alterations in expression of two genes in the phytomelatonin biosynthetic pathway, using overexpression of caffeic acid O-methyltransferase (COMT) and antisense silencing of serotonin N-acetyltransferase (SNAT). Plant leaflets were assessed for disease resistance by inoculation with Alternaria solani (early blight) and Phytophthora infestans (late blight). Exogenous application of melatonin did not increase resistance to either pathogen in detached leaflet assays. Melatonin applications did increase total tuber weights in the greenhouse by 8 to 30 percent depending on the cultivar tested. Endogenous modification of melatonin biosynthetic genes did not affect disease resistance, while phenotypic alterations were notable. Although the SNAT silenced plants had normal phenotypes, the COF overexpression resulted in short, thickened stems and leaves along with undersized, misshaped tubers, indicating that COF overexpression is undesirable for modification of endogenous melatonin levels.