First Report of Papaya ring spot virus (PRSV) Infecting Jute (Corchorus olitorius) in India

Jute is the most important bast fibre crop of the world, which is mainly cultivated in India, Nepal, Bangladesh, China, Indonesia and South American countries. The fibre is utilized for making apparels, ropes, bags, carpets etc (Biswas et al. 2014). This bio-fibre is gaining importance due to growing environmental consciousness worldwide. In June 2019, we noticed jute plants (less than 2%) showing virus like symptoms viz., downward curling, puckering, angular brownish to yellowish spots etc in a farmer's field at Amdanga Block, North 24 Paraganas, West Bengal, India. To identify the virus, five symptomatic leaves from five different plants were used for high throughput sequencing (HTS). We extracted total RNA from each leaf which was subjected to construction of cDNA libraries. Sequencing was done on Illumina Hiseq 4000 (CytoScan, Thermo Fisher). Approximately 46 million 105 nt paired end reads were generated. Raw reads were trimmed and filtered to perform de novo assembly as described previously by (Grabherr et al. 2013). The obtained contig was 10,326 bp nucleotides (nt) long and in BLASTn against GenBank showed highest identity with papaya ring spot virus (PRSV) with the contig covering 99.6% of the viral genome. The obtained contig shared 99.33% sequence similarity with PRSV strain P (Accession No. MT470188). The selected leaf samples were also tested by double-antibody sandwich (DAS)- enzyme linked immunosorbent assay (ELISA) for papaya ring spot virus (PRSV) along with some common viruses, viz., Potato leaf roll virus (PLRV), Watermelon mosaic virus, Cowpea mosaic virus and Cucumber mosaic virus with the help of commercial diagnostic kits (Agdia). However, only the test with PRSV gave positive reaction for the symptomatic samples. The major symptoms of PRSV on papaya are severe mosaic, chlorosis, reduced lamina with curling and puckering (Gonsalves et al. 2010). To confirm PRSV infection, five symptomatic leaf samples (used for HTS) were collected and whole RNA was extracted from the samples using RNeasy plant minikit (Qiagen, USA). Reverse transcriptase polymerase chain reaction (RT-PCR) was conducted by using isolated RNA. One pair of PRSV specific primer (PSRV1F: 5' TTAAATCTGATTCGTC 3' PRSV 1R: 5'GAAATTCACGCAAAGTCGA3') was developed by using primer BLAST software and was used in RT-PCR assays. Amplified fragments were cloned and sequenced and all the fragments shared 98% sequence identity with PRSV. One of the amplicons was deposited in NCBI (Accession No. MN615832). Crude sap was prepared by homogenizing PRSV-infected jute leaf tissues in 0.1 M sodium phosphate buffer and 2% carborundum dust was added as abrasive (Holkar et al. 2018). The sap was then gently rubbed on to the healthy papaya leaves for inoculation. Typical PRSV like symptoms appeared in inoculated leaves 10 days post inoculation which confirmed the presence of PRSV-P. PRSV was detected by RT-PCR as well as (DAS)-ELISA from all inoculated infected papaya leaf tissues, but could not be detected from uninoculated healthy papaya tissues. To the best of our knowledge, this is the first report of PRSV-P infecting jute in India. References: Biswas, C. et al. 2014. Plant Dis. 98(4): 565. https:// doi.org/10.1094/PDIS-08-13-0826-PDN. Gonsalves, D. et al. 2010. The Plant Health Instructor. https:// doi.org/10.1094/PHI-I-2010-1004-01 Holkar, S. K. et al. 2018. Crop Protection. 108:110-119. https://doi.org/10.1016/j.cropro.2017.12.013 Grabherr, M. et al. 2011. Nat Biotechnol. 29(7): 644-652.