New anthracnose disease caused by Colletotrichum orchidearum on Cattleya sp. orchid in India

Cattleya sp. is high value tropical orchid gaining huge popularity due to its great aesthetic value in West Bengal among the non- conventional agriculturist growers. In August, 2017 to February, 2018 and August, 2018 to February, 2019, new anthracnose disease with initial symptoms characterized by: Blight lesions from margin of the leaves forming greyish to whitish centre surrounded by irregular deep brown colour covering large area were observed on Cattleya sp. of orchid in a nursery at Arambagh, Hooghly District, West Bengal, India (23⁰69’80’’N, 87⁰67’34’’E).Disease incidence and severity were recorded up to 22.67% and during survey in January month Cattleya sp. was found to infest with anthracnose where disease severity was recorded up to 23.00%, respectively. The fungus was isolated from the diseased leaves and tentatively identified as Colletotrichum orchidearum based on cultural and morphological characteristics such as spore and acervulus characters. Partial DNA sequences of the ITS1 and ITS4 of the rRNA gene of Small Sub Unit (SSU) of the representative isolate CATA was found to be 100% similar with that of Colletotrichum orchidearumstrain LZJZ6 (Accession number: MK796541, China) and Colletotrichum orchidearum strain LL29-1-3 (Accession number: OM666546, China) obtained from NCBI database. Phylogenetic analysis using the internal transcribed spacer (ITS) region sequences indicated that the isolate CATA (MT158680) was closely related with Colletotrichum orchidearum strain LZJZ6 (Accession number: MK796541) and Colletotrichum orchidearum strain LL29-1-3 (Accession number: OM666546) and clustered together in as a single group with other deposited isolates of Colletotrichum orchidearum (OM666547 from China, MT114868 from Sri Lanka and MT299587 from Brazil). Isolates CATA was found to be pathogenic on the Cattleya sp. orchid. This is the first report of Colletotrichum orchidearum as the causal organism of Anthracnose disease in Cattleya sp.orchid in India.