Resistance of melon to Cucumber Vein Yellowing Virus (CVYV).
Cucumber vein yellowing virus (CVYV) belongs to the Ipomovirus genus, family Potyviridae. It is transmitted by the whitefly Bemisia tabaci, but can be transmitted mechanically in artificial inoculation. A collection of 1188 melon accessions has been inoculated with a CVYV strain isolated from melon in Spain. Five phenotypes have been observed: 46% of the accessions are susceptible with mosaic and vein-banding symptoms like the control Védrantais; 50% are highly susceptible with a severe mosaic, yellowing and stunting. Ouzbeque 2 is one of these accessions; few accessions exhibited necrotic symptoms with a rapid death of the plants. HSD 93-20-A from Sudan is a representative of this phenotype; only one accession (HSD 2458 from Sudan) was tolerant with very mild mottle but the virus can be detected by DAS-ELISA or RT-PCR in the plant apex; only an inbred line derived from the accession PI 164323 from India was resistant, exhibiting no symptom and the virus cannot be detected in non-inoculated leaves either by DAS-ELISA or RT-PCR. Inheritance of these behaviours was studied in F1, F2 and BC progenies between the above mentioned accessions. Three loci seem to be involved. At a first locus tentatively named Cucumber vein yellowing resistance (symbol Cvy-1), three alleles have been identified: Cvy-1+ for susceptibility (present in Védrantais), Cvy-11 controlling resistance in PI 164323 and Cvy-12 controlling necrosis in HSD 93-20-A. At an independent second locus, the recessive allele cvy-2 present in HSD 2458 controls the tolerance. And at a third locus the allele Cvy-3, present in Ouzbèque 2, controls the highly susceptible type of symptoms.