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Detection, diversity and distribution of Phytophthora species associated with citrus decline in India

Ashis Das: ICAR-Central Citrus Research Institute

<div><em>Phytophthora </em>spp. induce an array of diseases <em>viz.</em> root rot, crown rot, foot rot, gummosis and brown rot of fruits in citrus causing severe decline and yield losses in India. Between 2008 and 2016, over 300 citrus orchards in fifteen states (Maharashtra, Punjab, Rajasthan, Madhya Pradesh, Karnataka, Andhra Pradesh, Tamil Nadu, Odisha, West Bengal, Sikkim, Nagaland, Assam, Tripura, Arunachal Pradesh and Mizoram) were surveyed for the occurrence of <em>Phytophthora</em>. <em>P. nicotianae</em> was found predominant species followed by <em>P. palmivora</em>. A total of 257 isolates belonging to 11 different <em>Phytophthora</em> species (180 isolates of <em>P. nicotianae</em>, 47 isolates of <em>P. palmivora</em>, 7 isolates <em>P. citrophthora</em>, 9 isolates of <em>P. insolita</em>, 4 isolates of <em>P. boehmeriae,</em> 3 isolates of <em>P. heveae</em>, 2 isolates of <em>P. tropicalis,</em> 2 isolates of <em>P. macrochlamydospora, </em>1 isolate of <em>P. inundata </em>1 isolate of <em>P. virginiana-</em>like and 1 isolate of <em>P. lacustris</em>) were recovered from rhizosphere soil and water, root, leaf, bark and fruit samples. Isolates were identified to the species level through morphological traits, PCR-RFLP analyses of the internal transcribed spacer (ITS) region and sequence analyses of the ITS region, β tubulin gene, translation elongation factor 1α and cox 1 and 2 gene fragments. Detection of new spp. adds to the biodiversity of citrus <em>Phytophthora</em> in India. Pathogenicity tests supported their possible involvement in the decline of citrus plantations in different parts of India.</div>