First Report of Bacterial Leaf Spot Caused by Xanthomonas campestris pv. olitorii on Jute Grown for Seed in India.

Jute (Corchorus olitorius L.) is the second most important fiber crop after cotton in terms of global production (3). In November 2011, symptoms suggestive of bacterial infection were observed on a seed crop of jute at the CRIJAF research farm, Barrackpore, West Bengal, India. The disease appeared as small, brown, circular spots, usually less than 5 mm in diameter on the leaves and some of the spots were surrounded by a yellow halo. The lesions on the stems were elongated and in some cases were found to girdle the stem. In the later stages of disease, brown sunken spots were found on the green capsules. Disease incidence varied from about 20% to 90% of the total plants in different affected fields at the CRIJAF research farm. Bacterial leaf spot of jute with similar symptoms was reported in 1957 from Sudan (4). Five symptomatic and three asymptomatic leaf samples were collected from different jute fields. Bacterial colonies isolated on nutrient agar medium from infected young leaves were Xanthomonas-like and pale yellow cream in color. Total DNA was extracted from symptomatic as well as asymptomatic leaf samples by using an improved salt concentration and simple sodium acetate CTAB method (2). Single bacterial colonies were transferred to nutrient agar (NA) medium plates and incubated at 28°C for 48 h. Pure colonies from plates were used directly for DNA extraction using the QIAGEN DNeasy Blood and Tissue kit. PCR was carried out with Xanthomonas campestris specific primers NZ8F3/NZ85R3 (1), which generated an amplicon of 530 bp from all the symptomatic leaf samples as well as pure cultures of the isolated bacteria. No amplification was obtained from asymptomatic leaves. The amplicons from the five symptomatic samples collected from the field were sequenced and showed 100% identity with one another, and one sequence (strain JB-CO-13) was deposited in GenBank (Accession No. KC342185). The BLASTn analysis revealed that bacterial strain JB-CO-13 had 100% identity with X. campestris pv. olitorii (EU285213). Nucleotide span and ORF finder (NCBI) analysis indicated the 530-bp PCR amplicon coded part of a gyrase B gene that had 100% identity with a translated gene product (Protein ID: ABX84334). Three leaves of five 1-month-old jute plants (cv. JRO 204) in pot culture were infiltrated each with a separate bacterial strain using suspensions (1 × 10 CFU/ml) in distilled water. The negative control consisted of leaves infiltrated with sterile distilled water. The plants were kept in a greenhouse with mean maximum and minimum temperatures of 28.96 and 21.8°C, respectively. The plants were covered with plastic bags to maintain high relative humidity (>80%). Typical bacterial lesions were recorded on all the inoculated plants after 1 week. No lesions were seen on the negative control. To the best of our knowledge, this is the first report of bacterial leaf spot on C. olitorius caused by X. campestris pv. olitorii from India. References: (1) J. Adriko et al. Plant Pathol. 61:489, 2012. (2) C. Biswas, et al. Lett. Appl. Microbiol. 56:105, 2013. (3) Food and Agriculture Organization of the United Nations. Agricultural Commodities: Profiles and Relevant WTO Negotiating Issues. Online: http://www.fao.org/docrep/006/Y4343E/y4343e03.htm , 2003. (4) K. A. Sabet. Ann. Appl. Biol. 45:516, 1957.