The complete nucleotide sequence of isolates of Cucumber vein yellowing virus (CVYV) has been determined. The viral genome comprises 9734 nucleotides, excluding a 3'-terminal poly(A) sequence. The genome of CVYV has a 5'-non coding and a 3' non coding region of respectively 67 and 240 nucleotides. The RNA of CVYV encodes a single polyprotein of 3148 amino acid residues and has a deduced genome organization and motifs typical for a member of the family Potyviridae. However, CVYV is atypical because it lacks a coding sequence region for the putative helper-component as well as conserved helper-component-proteinase motifs which may account for its vector relations. All the present coding regions were compared to those from several members of the Potyviridae family. CVYV is most closely related to Sweetpotato mild mottle virus confirming its assignation to the genus Ipomovirus, despite similarities with tritimoviruses.

Cucurbit yellow stunting disorder virus (CYSDV) has been present in greenhouse-grown cucumber in Spain since 1992. However, in the autumn of 2000 Cucumber vein yellowing virus (CVYV) was introduced, leading to mixed infections of both Bemisia tabaci -transmitted viruses. The temporal and spatial spread of disease symptoms were monitored in experimental plastic-covered greenhouses during six consecutive cucumber plantings from 2000 to 2002. Using linear regression analysis of 46 disease-progress curves, the Gompertz model best described the CYSDV epidemics in 2000, whereas the logistic model best described the development of CYSDV and CVYV epidemics in 2001 and 2002. The fitted models were used to calculate the amount of degree Celsius-days at half-maximum infection in the greenhouses ( ° D 0·5 ). After multiple regression analysis, 56% of the variation in ° D 0·5 of CYSDV was related to the numbers of whiteflies infesting the cucumber crops, and was independent of the mean temperatures in the greenhouses. In contrast, 76% of the variation in ° D 0·5 of CVYV was related to both the numbers of vectors present and maximum temperature. Symptom expression in cucumbers mechanically inoculated with CVYV was most prevalent when plants were grown at regimes of at least 28 ° C day temperature. According to analysis of spread using Taylor's power law, beta-binomial distribution fitting, and the ordinary runs test, the prevalence of CVYV showed significant overdispersion, whereas that of CYSDV did not. The χ 2 test of independence and Spearman's rank correlation coefficient were used to measure co-occurrence and covariation, respectively, during the first half of the cultivation period. These results showed that the two diseases were not associated.

The population structure and genetic diversity of Cucumber vein yellowing virus (CVYV) from Spain were estimated by analyses of partial nucleotide sequences of the P1-proteinase (P1-Pro), P3 protein (P3), and the coat protein (CP) coding regions. Analysis of 56 CVYV Spanish field isolates collected from 2001 to 2005 showed low genetic diversity (0.0026, 0.0013, and 0.0012 for the P1-Pro, P3, and CP regions, respectively). The ratio between nonsynonymous and synonymous substitutions was among the lowest found in a plant virus, indicating a strong negative selective pressure in the regions analyzed. Nonsynonymous nucleotide substitutions were only found within the P1-Pro regions, although these do not appear to have been selected with time. The results support the hypothesis that the Spanish CVYV population could derive from a single origin of recent introduction.

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A study was conducted to determine the identity and prevalence of viruses in 455 greenhouses in the main Spanish green bean growing area. Directed surveys were conducted in 422 crops from 2000-2004 to collect samples from diseased plants displaying symptoms that could be attributed to viruses. The samples were analysed to detect any virus by means of dsRNA extraction, mechanical inoculation to test plants, as well as ELISA and/or RT-PCR tests to detect potyviruses, geminiviruses and viruses previously known to infect beans in Spain. Random surveys were conducted in the years 2002 and 2005 (in 21 and 12 greenhouses, respectively) to study the actual incidence of known viruses in the area. Symptoms were recorded in 23,108 plants from which 664 plants were collected and analysed by ELISA or RT-PCR. The results of the directed surveys showed that all the analyzed crops carried the cryptic virus Phaseolus vulgaris endornavirus (PVuV), whereas phytopathogenic viruses appeared in smaller percentages of the crops: Tomato yellow leaf curl virus (TYLCV) 20.4%, Southern bean mosaic virus (SBMV) 9.0%, Tomato spotted wilt virus (TSWV) 4.0%, and the new species Bean yellow disorder virus (BnYDV) that broke out in 2004 with occurrence values higher than 34.3% that year. From 2000-2004 an important decrease in TYLCV was observed, along with a slight increase in SBMV and a consistently low occurrence of TSWV. The results of the random surveys confirmed the increased occurrence of virus detected during the directed surveys, and furthermore demonstrated the percentage of incidence for each virus.

Amaranthus leaf mottle virus (AmLMV) was classified as a member of the genus Potyvirus on the basis of its particle morphology, serology, and biological properties (Casetta et al., 1986). Based on these properties, an Amaranthus viridis-infecting virus isolated in Spain, causing mottle and leaf blistering as well as reduced growth has been identified as AmLMV. The 3¢ terminal genomic region of this and a reference isolate from Italy has been sequenced and reveals a 95% nucleotide identity between the two isolates. The sequenced part comprises the coat protein with 281 amino acids and 315 nucleotides of the 3¢ untranslated region (UTR) preceding a polyadenylated tail. Pairwise comparisons and phylogenetic analysis of the nucleotide and deduced amino acid sequences of the CP and 3¢ UTR of the cloned cDNAs with those of other potyviruses shows that AmLMV is a distinct potyvirus closely related to Potato virus Y.