The distribution and prevalence of Papaya ring spot virus (PRSV) in Kenyan papaya.

摘要

At an estimated 86,000 tons, Kenya's annual fruit production of papaya (Carica papaya L.), represents approximately 1.2% of global yield. The Papaya ring spot virus presents one of the greatest constraints to production worldwide, causing significant decline in fruit yield and economic life span of the plant. The objective of this study was to determine the distribution and prevalence of the virus in the main papaya growing regions of Kenya. Surveys were conducted between June 2008 and December 2010, through six Kenyan provinces of Central, Coast, Eastern, Rift Valley, Nyanza and Western province. Total 516 plants were sampled from 54 sites and the presence/absence of symptoms on representative plants was used to evaluate disease prevalence. Disease severity was quantified based upon a subjective scale of 1-5. Symptomatic plants were observed in all provinces at mean prevalence level of 23%, while severity indices ranged between 1.2 and 3.5. Double Antibody Sandwich Enzyme linked Immuno-Sorbent Assays (DAS-ELISA) however proved ambiguous. Reverse transcription polymerase chain reaction (RT-PCR) however presented a strong correlation between symptom expression and molecular diagnostic test results. Five sites, located in Coast, Western, and Eastern provinces respectively, presented asymptomatic populations of papaya. This suggests the need for development of alternate serological test methods for PRSV and recommends further study to determine the extent of sequence variation within Kenyan isolates of PRSV.