Mixed infection with Colletotrichum species and Alternaria alternata causes fruit rot on processing tomato fruits

Abstract

Severe fruit rot was observed on ripe processing tomatoes in an open field in Japan. Round, sunken lesions formed on the fruits, with numerous black conidia in the center; the rot eventually expanded, sometimes over the entire fruit. Fungal isolates from lesions on the fruits were identified as Colletotrichum cliviicola, C. fioriniae and Alternaria alternata based on phylogenetic analysis. Isolates of C. cliviicola and C. fioriniae caused sunken lesions with ochre to blackish colonies on ripe but not unripe tomatoes. The A. alternata isolates also caused sunken lesions with white to blackish colonies only on ripe fruits. Thus, C. cliviicola, C. fioriniae, and A. alternata caused the fruit rot on processing tomatoes. Sequential inoculation of processing tomato fruits with C. cliviicola and A. alternata also caused symptoms similar to those in the field, suggesting that a mixed infections can lead to this severe fruit rot.