Papaya ringspot virus isolates from papaya in Bangladesh: detection, characterization, and distribution

Authors: HAMIM, ISLAM - University Of Hawaii; AL RWAHNIH, MAHER - University Of California, Davis; BORTH, WAYNE - University Of Hawaii; Suzuki, Jon; MELZER, MICHAEL - University Of Hawaii; Wall, Marisa; GREEN, JAMES - University Of Hawaii; HU, JOHN - University Of Hawaii

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/3/2019
Publication Date: 9/26/2019
Citation: Hamim, I., Al Rwahnih, M., Borth, W.B., Suzuki, J.Y., Melzer, M.J., Wall, M.M., Green, J.C., Hu, J.S. 2019. Papaya ringspot virus isolates from papaya in Bangladesh: detection, characterization, and distribution. Plant Disease. 103(11):2920-2924. https://doi.org/10.1094/PDIS-12-18-2186-RE.
DOI: https://doi.org/10.1094/PDIS-12-18-2186-RE

Interpretive Summary: Papaya ringspot virus (PRSV) is an insect-vectored disease of papaya and a primary constraint to global papaya production. In this paper, we determined the full-length coding sequences of two PRSV isolates from virus-infected papaya plants in Bangladesh. The genome sequences were unique compared to known strains from many different countries. Detection assays were developed that are capable of identifying two strains of PRSV in the same papaya plant. Results can be used to develop transgene-derived PRSV resistance for papaya produced in Bangladesh.

Technical Abstract: Papaya ringspot virus (PRSV) is the major constraint in papaya (Carica papaya) production in Bangladesh. Incidence of virus-like disease symptoms occurred in 90-100% of the plants surveyed. Most of the symptomatic plants were severely affected, with stunted growth, and a severe reduction in fruit yield and quality compared to asymptomatic plants. Full length coding genomes of PRSV strains from severely infected papaya plants were determined by the Illumina NextSeq 500 platform and Sanger DNA sequencing of viral genomes obtained by reverse transcriptase polymerase chain reaction (RT-PCR) amplification. The genome sequences of two distinct PRSV strains, PRSV BD -1 (10,300bp) and PRSV BD -2 (10,325bp), from severely virus-infected papaya plants were obtained, representing the first complete coding genomes of PRSV strains reported from Bangladesh. The two PRSV strains from Bangladesh are 74% and 83% identical to each other at the nucleotide and deduced amino acid levels, respectively. PRSV BD-1 and PRSV BD-2 were 74-75% and 79-88% identical, respectively, with other completely sequenced PRSV isolates at the nucleotide level. Based on phylogenetic sequence analysis, PRSV BD-2 was most closely related to PRSV-Meghalaya (MF356497), a strain of PRSV infecting papaya in India, whereas PRSV BD-1 formed a distinct branch from the other PRSV sequences by nucleotide, as well as amino acid, sequence comparisons. Comparisons of the genome sequences of these newly identified PRSV strains with other sequenced PRSV genomes indicated two putative recombination events in PRSV BD-2. One recombinant event contained a 2766 nucleotide fragment maximum identical to PRSV-Meghalaya (MF356497) and the other contained a 5105 nucleotide fragment maximum identical to PRSV-China (KY933061). The occurrence of PRSV BD-1 and PRSV BD-2 in sampled areas was approximately 19% and 69%. Plants infected with both strains (11%) exhibited more severe symptoms than plants infected with either strain alone. The new full-length genome sequences of these PRSV strains from Bangladesh and their distribution within the country provide important information relating to the dynamics of papaya ringspot virus infections in papaya in Bangladesh.