COMPARISON OF DOT-BLOT, ELISA, AND RT-PCR ASSAYS FOR DETECTION OF 2 CUCUMBER MOSAIC-VIRUS ISOLATES INFECTING BANANA IN HAWAII

The coat protein genes of two cucumber mosaic virus (CMV) isolates infecting banana plants in Hawaii were cloned and sequenced. Based on nucleotide and amino acid sequence comparisons, both isolates belong to CMV subgroup I. One isolate (CMV-Hawaii), which is common in banana plants in the state of Hawaii and induces mild mosaic symptoms, shares 99% sequence identity (both nucleotide and amino acid sequences) with CMV-C strain. Another isolate (CMV-Oahu), which was found only at two banana farms in the state of Hawaii, induces severe mosaic and leaf distortion symptoms. CMV-Oahu shares 91% and 93% nucleotide and amino acid sequence identity, respectively, with both CMV-C and CMV-Hawaii. A reverse transcription-polymerase chain reaction (RT-PCR) assay was developed for detection of both CMV subgroups from banana samples. The RT-PCR product (similar to 750 bp) was also labeled as a probe to detect CMV in dot blot hybridization tests, PCR is a more sensitive assay than either dot blot or ELISA. The dot blot assay was 100 times more sensitive than ELISA. The distribution of CMV within banana plants was uneven. CMV concentrations were higher in younger leaves than in older ones, The CMV-Oahu isolate was not detected in banana by ELISA using antibodies to both CMV subgroups I and II, but was positive in dot blot and RT-PCR tests.