Selection of watermelon accessions for resistance to some important potyvirus species based on serological evaluation

Abstract

We used 19 genotypes (plus controls) of watermelon from the collection of Cucurbitaceas germplasm of the Federal Rural University of the Semi-Arid to select watermelon plants resistant to Papaya ringspot virus “type Watermelon” (PRSV-W), Watermelon mosaic virus (WMV), and Zucchini yellow mosaic virus (ZYMV). Twenty individual plants were tested for each genotype/accession. Three controls were also used (3 genotypes). Evaluations were performed under greenhouse in a completely randomized design with five replications. The first inoculation was performed on the seedlings before the appearance of the first definitive leaf. From each accession (genotype) 20 different individual plants were inoculated with the three viruses. The inoculum was prepared by infected leaf tissue. The viral suspension and gauze soaked in extract were wiped on the surface of the leaves. Ten days later, the symptom assessment was performed. Subsequently, the plants were individually tested against the specific viruses using indirect ELISA. ELISA negative plants were submitted to a second inoculation under greenhouse, as described for the first inoculation. Ten days after new inoculation, new symptomatological evaluations and serological tests were performed to confirm the resistance of the plants. Plants that were negative by ELISA were tested by RT-PCR for confirmation of resistance. Resistance to the three viruses was verified individually in several tested genotypes. We found resistance to the three viruses tested, but in different plant individuals, where 16 individual plants were WMV-resistant, 26 PRSV-W resistant and 30 ZYMV-resistant. These plants can be used to develop homozygous lines for resistance to the virus studied.