Genetic Diversity in Monilinia laxa Populations in Peach Orchards in Spain

A disease characterized by symptomless leaves and fruit decolouration, loss of consistency and mild deformation on ripening was detected in tomato fields in north-eastern Spain during 2003 and 2004. DASELISA analysis revealed the presence of the Cucumber mosaic virus (CMV) in all diseased plants. CMV isolates were characterized by polyacrylamide gel electrophoresis (PAGE) analysis of double-stranded RNAs (dsRNAs) and nucleotide sequence analysis, and compared with some CMV isolates belonging to different subgroups used as controls. A total of 12 isolates obtained from the infected tomato plants selected for this study gave the same electrophoresis pattern for the three genomic dsRNAs, which was different to the patterns showed by the CMV isolates collected in the same region a few years ago. The identity of the complete nucleotide sequence of one of these CMV isolates and the partial sequence of other five isolates compared to the Tfn strain from Italy and the BAR92/1 isolate from tomato collected in Barcelona in 1992 was higher than 99%, both belonging to subgroup IB of CMV. The CMV isolates of this subgroup found in eastern Spain in previous studies were not detected after 1996. The nucleotide sequences of two isolates that were chosen as representatives of the CMV isolates more frequently detected in previous years revealed that they belonged to the CMV subgroups IA. The origin and the possible causes of reappearance of CMV IB isolates in north-eastern Spain are discussed