The watermelon, Citrullus spp., can be infected by several virus species from the Potyviridae family. In the Universidade Federal do Ceará (Brazil), a research program was started to identify sources of resistance to Papaya ringspot virus type watermelon (PRSV-W), Watermelon mosaic virus-2 (WMV-2) and Zucchini yellow mosaic virus (ZYMV) utilizing accessions from the watermelon germplasm bank from Embrapa Semi-Árido in Petrolina. In the green house experiments, 4 plants of each accession were inoculated, separately, with PRSV-W, WMV-2 and ZYMV, 8 days after planting date. Four plants from each accession were maintained as control not inoculated. The symptoms appeared in 10 days, after inoculation, in the susceptible accessions. Fifteen days after the first inoculation, the plants without symptoms were re-inoculated. Twenty-five days after the first inoculation the accessions were evaluated through ELISA test, against the 3 virus antisera and the plants without symptoms gave negative results. Five accessions were resistant to three virus, 3 of them from Citrullus lanatus, one from C. lanatus var. citroides and other from C. colocynthis. Only one accession was resistant only to PRSV-W, 21 were resistant only to ZYMV and neither one presented resistance only to WMV-2. Nevertheless, 45 accessions showed resistance to ZYMV alone and in combination with other potyviruses. Some accessions can be crossed in order to obtain plants with triple resistance in segregating populations for plant and fruit characters, increasing the genetic variability of the sources of resistance to the main watermelon potyvirus.
Citrullus spp.; Potiviridae; watermelon germplasm
