Occurrence of Phytophthora Nicotianae Causing Collar and Root Rot Disease of Chrysanthemum in India

Chrysanthemum is an important flower crop grown in different parts of the world. Apparently there are new reports of chrysanthemum collar rot and root rot caused by Phytophthora sp. around the world. In recent years there has been increase in incidence of Phytophthora root and collar rot in chrysanthemum and no information is available about this disease in India. Therefore the aim of the present study is to isolate and characterize the pathogen causing collar rot and root rot disease of chrysanthemum. During year 2021, the plants exhibiting collar rot and root rot disease symptoms were received from the local farmers. Based on initial micro-morphological observation it was identified as Phytophthora sp. Further the pure culture of pathogen was isolated and confirmed its identity through cultural, morphological and amplification of the three regions/genes (ITS, tef-1α and β-tubulin) of Phytophthora sp. Phylogenetic analysis of concatenated sequence derived from ITS, tef-1 and β-tubulin sequences of five Phytophthora isolates (PhN1, PhN2, PhN3, PhN4 and PhN5) showed close clustering of these isolates with Phytophthora nicotianae isolates infecting different crops. This is first detailed characterization of Phytophthora nicotianae causing collar rot and root rot in chrysanthemum in India.