Effect of 1-methylcyclopropene on the development of black mold disease and its potential effect on alternariol and alternariol monomethyl ether biosynthesis on tomatoes infected with Alternaria alternata

• 1-MCP could increase growth of A. alternata if conditions favor fungal development.
• In 1-MCP treated tomatoes, mycotoxin biosynthesis depends on tomato variety.
• Although no mycotoxin was detected at 6d-10 °C, pksJ gene expression was observed.

Ethylene is a naturally produced plant regulator involved in several plant functions, such as regulation of fruit ripening. Inhibition of ethylene perception by using 1-methylcyclopropene (1-MCP) slows down the ripening of the fruit maintaining its quality and freshness. The use of 1-MCP is a commercial strategy commonly used in the food industry to extend the postharvest life of several fruits, including tomatoes. To assess how 1-MCP affected infection by Alternaria alternata on tomatoes, three different cultivars were artificially inoculated with 5 μL of an A. alternata conidial suspension (105 conidia/mL). Tomatoes were treated with 0.6 μL/L of 1-MCP for 24 h. Spiked but untreated tomatoes were considered controls. Then, fruit were stored 6 days at 10 °C and one more week at 20 °C to simulate shelf-life. Fungal growth development and mycotoxin production (alternariol, AOH and alternariol monomethyl ether, AME) were assessed both on the first and on the second week. After the first 6 days at 10 °C, in just one variety the black mold disease was higher in the 1-MCP treated samples. However, after two weeks of storage, in all cases, tomatoes treated with 1-MCP showed more significant fungal growth disease. Regarding mycotoxin production, no large differences were observed among different treatments, which was corroborated with gene expression analysis of pksJ, a gene related to AOH and AME biosynthesis.