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Two hundred and sixty-eight Cucumis melo and wild relative accessions were evaluated for resistance to Cucumber mosaic virus (CMV), Papaya ringspot virus strain W (PRSV-W), Watermelon mosaic virus (WMV), and Zucchini yellow mosaic virus (ZYMV). Symptom development and systemic infection based on double antibody sandwich enzyme-linked immunosorbent assays were monitored. Sources of resistance were scarce. However, a number of them were found among the C. melo accessions tested. Thus, the accession C-189 behaved similarly to PI 161375 and showed resistance to "common" CMV strains although it was infected by a "song" type CMV. For WMV, the accessions C-768 and C-425, although infected, exhibited very mild symptoms, and recovery from infection occurred in some occasions in the former. A similar trait was also found in C-105, although in this case symptoms rarely appear and part of the plants are not infected. In addition, C-105 was highly resistant to virus transmission by Aphis gossypii, similarly to PI 161375. Accessions C-885 and C-769 exhibited resistance to PRSV-W, WMV, and ZYMV; therefore they are potential sources of multiple resistance. Resistance traits were also found in wild relatives that could be exploited when interspecific barriers with C. melo can be circumvented.

Since 1997, yellowing disease outbreaks have occurred in tomato (Lycopersicon esculentum) crops in southern Spain. The outbreaks were associated with high populations of the whitefly Bemisia tabaci. Symptoms consisted mainly of interveinal yellowing that developed initially on lower leaves and then progressed to the upper part of the plant. Affected plants were less vigorous and yielded less due to reduced fruit growth and delayed ripening. During 1998 and 1999, the yellowing disease was widespread and occurred at high incidences in the Málaga province. The disease agent was readily transmissible from tomato to tomato by B. tabaci biotype Q. Samples from symptomatic tomato plants were analyzed and shown to be infected with Tomato chlorosis virus (ToCV) (genus Crinivirus, family Closteroviridae). This is the first report of ToCV epidemics in Europe.