IDENTIFICATION OF CUCUMBER MOSAIC-VIRUS SUBGROUP-I ISOLATES FROM BANANA PLANTS AFFECTED BY INFECTIOUS CHLOROSIS DISEASE USING RT-PCR

Reverse transcription-polymerase chain reaction (RT-PCR) assays, restr iction enzyme analysis, and comparison of nucleotide sequences were us ed to identify isolates of cucumber mosaic cucumovirus (CMV) that belo ng to subgroup I from infectious chlorosis-affected banana plants. Inf ected samples were from irrigated banana plantations at Carnarvon in t he semiarid Gascoyne region of central Western Australia, and from Kun unurra in the northern tropical Kimberley region. An RT-PCR assay with primers designed in a conserved region of the 3' end of the CMV coat protein gene amplified a 486- to 488-bp DNA fragment from infected ban ana samples. CMV was detected in leaf blades, midrib, and pseudostem o f infected plants, but not in asymptomatic plants. Restriction enzyme analysis of PCR products using EcoRI and MspI showed that the samples tested from diseased banana were infected with CMV subgroup I isolates . This result was confirmed by sequencing PCR-amplified products, whic h showed 98% homology to sequences of CMV subgroup I isolates but only 76% homology to sequences of CMV subgroup II isolates. The RT-PCR is a reliable assay to detect CMV in banana plants and, when combined wit h restriction enzyme digestion, provides a simple means of identifying the CMV subgroup present.