First report of rice grain discolouration and leaf blight caused by Pantoea ananatis in the Kuttanad agro-ecosystem, Kerala, India

Abstract

Rice is one of the most important staple food crops, and bacterial diseases are among the major limitations to its productivity and yield. Kuttanad is a unique agro-climatic region in Kerala, India, where rice cultivation occurs below sea level. It is recognized as a Globally Important Agricultural Heritage System by the Food and Agriculture Organization of the United Nations. In July 2021, grain discolouration and leaf blight symptoms were noted on rice plants in the field. Leaves developed yellowish to brown lesions, which turned a pale white to straw colour as the disease progressed. Bacteria were isolated from symptomatic leaves and grains. The pathogenicity of a recovered bacterial strain was assessed by artificial inoculation and Koch’s postulates were met. Re-isolation of the pathogenic strain showed high similarity with the originally recovered strain. The 16S rRNA gene was sequenced (accession no. OK398432) and found to have 100% similarity with Pantoea ananatis, an emerging pathogen of rice. To our knowledge, this is the first report of P.ananatis from the Kuttanad region of India.