Multi-gene phylogeny and phenotypic analyses revealed an association of different Colletotrichum species with inflorescence dieback and leaf spot of arecanut in India

Abstract

Arecanut is one of the economically important plantation crops. Among the various diseases, inflorescence dieback and leaf spot/blight diseases caused by Colletotrichum spp. have re-emerged as major factors impeding arecanut production in India in the last few years. To understand the Colletotrichum species complex in the arecanut system, we have characterized Colletotrichum spp. associated with inflorescence dieback and leaf spot/blight of arecanut based on a combination of phenotypic, multi-locus (ITS, ACT, CHS-1, GAPDH, HIS3 and TUB2) phylogeny and pathogenicity studies. A total of 26 Colletotrichum isolates were obtained from arecanut inflorescence dieback (13 isolates) and leaf spot/blight (13 isolates) infected tissues collected from disease-endemic regions of Karnataka, Kerala and Tripura states of India. The combined multi-locus sequence analyses and a critical examination of phenotypic characters revealed the association of Colletotrichum aoteaora as a dominant species with arecanut inflorescence dieback disease. On the other hand, two Colletotrichum species, viz., C. siamense and C. fructicola, were distinctly associated with leaf spot/blight disease. All the Colletotrichum isolates studied were pathogenic to arecanut. Significant variations in lesion size were observed among the different species with cross-infection ability on inflorescence and leaves. This study represents the first comprehensive study of Colletotrichum spp. associated with arecanut inflorescence dieback and leaf spot/blight diseases. In addition, the study is the first record of C. aoteaora, C. siamense, and C. fructicola associated with the arecanut crop in this country. It provides valuable information for implementing effective IDM strategies against these diseases in India.