Grad student University of Massachusetts Amherst, Massachusetts
Body of Abstract: Steroidal glycoalkaloids (SGAs) are a group of secondary metabolites produced by Solanaceae plants in response to biotic stressors, including pathogen and herbivore attacks. Two well-known SGAs in cultivated tomatoes, α-tomatine and dehydrotomatidine, have been implicated in inhibiting fungal growth. However, little is known about the quantity and chemical diversity of SGAs in wild tomatoes and their potential antifungal properties across species. Our research aims to address this knowledge gap by identifying SGAs in 13 different wild tomato species and exploring the role of SGAs in inhibiting the growth of several fungal strains, including Fusarium oxysporum f.sp. lycopersici Mn25 (a tomato pathogen), Fusarium oxysporum Fo47 v2.0 (an endophyte strain), Cladosporium fulvum (a tomato specialist pathogen), and Colletotrichum coccodes (a generalist pathogen).
Our findings show that the amount of α-tomatine in the examined species ranged from 0.1-6 mg/g of leaf, while dehydrotomatine ranged from 0.05 to 1.8 mg/g of leaf. We observed high antifungal properties against one strain of Fusarium in the semi-domesticated tomato, Solanum lycopersicum var. cerasiforme, which had a relatively high SGA content. In contrast, S. habrochaites, a species with relatively low SGA levels, showed lower inhibition of Fusarium growth. Other wild tomato species showed medium levels of SGAs, and we are further investigating their antifungal properties against a diverse set of fungal species.
In conclusion, our results demonstrate that the chemical diversity of SGAs across wild tomato species can lead to varying levels of inhibition in the growth of Fusarium, providing insight into the co-evolution of wild tomatoes and their pathogenic fungi.