Association of Pseudomonas oryzihabitans with grain discoloration, panicle blight and chaffiness of rice in North India

Abstract

Rice is the dominant cereal crop of North India. It is regularly affected by grain discoloration and chaffiness of panicles during maturity of the crop. Lack of effective management practices for this problem has been a major concern among farmers in the region. Farmers give many sprays of fungicides due to the already reported association of fungal pathogens but fail to achieve the required control of this malady. It is necessary to know the correct etiology of this disease to successfully devise management options against this disease. We report the existence of Pseudomonas oryzihabitans associated with grain discoloration, panicle blight, and chaffiness of rice from the Punjab region of North India for the first time. During Kharif 2021, panicle blight symptoms (disease incidence 20–25%, cultivar PR 114) were observed in rice fields of three districts. These blighted panicles were partially filled or grains were aborted causing chaffiness in many panicles. Yellow-colored smooth, circular colonies of bacteria were obtained from the diseased panicles. The associated bacterium was identified as a rod-shaped, gram-negative P. oryzihabitans based on biochemical characterization, Scanning Electron Microscope imaging, and sequencing of the 16S rDNA region along with housekeeping genes rpoD and gyrB. The pathogenicity of the bacterium was tested in the fields during Kharif 2021 and Kharif 2022.The study demonstrated that the bacterial pathogen, P. oryzihabitans should be considered as one of the cause of grain discoloration and chaffiness of rice in Punjab region of India and management options for bacterial grain discoloration, panicle blight and chaffiness should be worked out for effective management of this disease.