IDENTIFICATION OF ZUCCHINI YELLOW MOSAIC POTYVIRUS BY RT-PCR AND ANALYSIS OF SEQUENCE VARIABILITY

A reverse transcription-polymerase chain reaction (RT-PCR) method was used to identify Zucchini yellow mosaic virus (ZYMV) in leaves of infe cted cucurbits. Oligonucleotide primers which annealed to regions in t he nuclear inclusion body (NIb) and the coat protein (CP) genes, gener ated a 300-bp product from ZYMV and also from the closely related wate rmelon mosaic Virus type 2 (WMV-2). However, no product was obtained f rom papaya ringspot potyvirus which also infects cucurbits. ZYMV and W MV-2 were differentiated using a third primer which was complementary to a sequence in the 3'-untranslated region; a 1186-bp amplified produ ct was obtained for ZYMV only. Nucleotide sequence analysis of the 300 -bp fragments of Australian ZYMV and WMV-2 strains revealed 93.7-100% sequence identity between ZYMV strains. Multiple sequence alignments i ndicated that the nucleotide sequence which codes for the N-terminus o f the CP was 74-100% identical for different isolates of ZYMV. The Aus tralian isolate of WMV-2 was 43-46% identical to all isolates of ZYMV and was 84.6% identical to a Florida isolate of WMV-2.