Two additional Colletotrichum species causing leaf spot of rambutan (Nephelium lappaceum)

Rambutan (Nephelium lappaceum) is an important fruit tree. Recently, leaf spots were observed in a tree in Los Banos, Laguna, Philippines. This study aims to identify the causal agent of rambutan leaf spot in the Philippines. Two fungal isolates, MBRAM001B and MBRAM003B, were isolated from the diseased leaves on potato dextrose agar medium. Colony growth and conidia characteristics of both isolates showed high resemblance with Colletotrichum species in the C. gloeosporioides species complex. Molecular characterisation of the isolates using the partial internal transcribed spacer rDNA and TUB2 regions identified the pathogens as C. tropicale MBRAM001B and C. siamense MBRAM003B. Leaf spots developed on rambutan leaves three days after inoculation and the same pathogens were isolated from the diseased leaves, establishing Koch's Postulate. In conclusion, this study identified C. tropicale MBRAM001B and C. siamense MBRAM003B as causal agents of leaf spots in rambutan species in the Philippines. The survival and possible infection of these two Colletotrichum species on rambutan fruits and other fruit trees are worth further investigating.