Characterization of New Bacterial Leaf Blight of Rice Caused by Pantoea stewartii subsp. indologenes in Southern Districts of Tamil Nadu

A survey was conducted in the rice fields of Tirunelveli, Tuticorin, Kanyakumari and Madurai districts of Tamil Nadu during 2016to assess the importance of bacterial leaf blight (BLB) of rice caused by Xanthomonas oryzae pv. oryzae. Bacterial Leaf Blight affected leaf samples showing yellowing symptoms or orange to brown stripes on one or both halves of the leaf blade were collected from seventeen places and maintained as isolates. Upon isolation, symptomatic leaf pieces were surface sterilized and placed in wakimoto semi-synthetic medium. The yellow pigmented, raised and translucent colonies with smooth margin were obtained after incubation at 28°C for 2 days. The biochemical characterization revealed that the bacteria belong to gramnegativefacultative anaerobes with small rods either arranged singly or in chains. Thirteen isolates show positive results in biochemical tests viz.,Gram staining, KOH test, starch hydrolysis, anaerobic growth test, tween 80 hydrolysis test, catalase test, citrate utilizationtest and production of yellow pigment on Yeast Dextrose Chalk agar medium. In virulence test, Isolate 1, Isolate 3 and Isolate 4 were considered virulent as they have caused severe blight symptoms both in TN1 and ADT 43, the susceptible check varieties. Based on 16S rRNA sequence analysis, the causal agent was identified as Pantoea stewartii subsp. indolegenes (Accession No. SUB2733370: MF163273; MF163274; MF16327). The biochemical and molecular analysis revealed that the causal agent was not Xanthomonas oryzae pv oryzae, but a new species of bacteriumnamely Pantoea stewartii subsp. indolegenes. This is the first report of new bacterial leaf blight disease of rice caused by Pantoea stewartii subsp.indologenesin southern districts of Tamil Nadu.