Mycotoxin production by isolates of Fusarium lactis from greenhouse sweet pepper (Capsicum annuum)

Internal fruit rot, caused by Fusarium lactis, is an important disease of sweet pepper (Capsicum annuum) in Canadian greenhouses. Production of the mycotoxins fumonisin B1 (FB1), moniliformin (MON) and beauvericin (BEA) by F. lactis (17 isolates) and the related species F. proliferatum (three isolates) and F. verticillioides (one isolate), which are also associated with internal fruit rot, was evaluated on rice medium. All 21 isolates examined were found to produce BEA, at concentrations ranging from 13.28 to 1674.60 ppm, while 13 of 17 F. lactis isolates and two of three F. proliferatum isolates produced MON (0.23 to 181.85 ppm). Only one isolate of F. lactis produced detectable levels of FB1 in culture, whereas all three F. proliferatum isolates and the F. verticilloides isolate produced this mycotoxin (0.28 to 314 ppm). Production of FB1, MON and BEA was also evaluated in inoculated pepper fruits showing mild or severe symptoms of infection. FB1 could be detected in both lightly and heavily diseased fruit tissue after inoculation with F. lactis, F. proliferatum or F. verticilloides, at concentrations ranging from 0.61 to 8.04 ppm. BEA was also detected in lightly and heavily diseased fruit tissue inoculated with F. lactis, as well as in heavily diseased tissue inoculated with F. proliferatum (3.00 to 19.43 ppm), but not in tissue inoculated with F. verticilloides. MON was detected in all tissues inoculated with F. proliferatum or F. verticilloides, and in heavily diseased tissue inoculated with F. lactis (0.03 to 0.27 ppm). The three mycotoxins were also found in naturally infected sweet pepper fruits exhibiting symptoms of internal fruit rot and collected from a commercial greenhouse. The production of MON, BEA and FB1 alone or in combination by isolates of F. lactis suggests that development of internal fruit rot of sweet pepper is an important food safety concern, and that every effort should be made to cull infected fruit before it makes it to market.

Research highlights
► Internal fruit rot is a major disease of greenhouse sweet pepper caused by Fusarium lactis.
► We study production of the mycotoxins fumonisin B1, moniliformin and beauvericin by F. lactis.
► All three mycotoxins are produced alone or in combination by fungal isolates.
► The mycotoxins are detected in vitro and in inoculated and naturally infected fruit.
► Internal fruit rot of sweet pepper is an important food safety concern.