M elon chlorotic mosaic virus and associated alphasatellite from V enezuela: genetic variation and sap transmission of a begomovirus–satellite complex

Begomoviruses represent one of the most damaging virus groups on many important crops worldwide. In V enezuela, the begomovirus M elon chlorotic mosaic virus ( M e CMV ) is the major constraint for melon and watermelon production. M e CMV has been associated with the satellite Melon chlorotic mosaic alphasatellite ( M e CMA ). Full‐length genome sequencing of 20 and 35 isolates of M e CMV and M e CMA , respectively, was carried out to estimate their genetic variability. Furthermore, mechanical transmission assays of M e CMV alone, or in conjunction with M e CMA , were performed. Genetic variation was low among M e CMV isolates, which exhibited 97–100% nucleotide identity for the DNA ‐A component and 95–100% for the DNA ‐B component. Alphasatellite isolates were highly variable ranging from 86·5 to 100% nucleotide identity. M e CMV isolates were phylogenetically related to begomoviruses belonging to the S quash leaf curl virus ( SLCV ) clade, while M e CMA isolates were clustered in two subgroups related to alphasatellites from the New World (Cuba and Brazil). M e CMV has a host range restricted to cucurbit species and two experimental hosts: N icotiana benthamiana and N icotiana clevelandii . M e CMV can be mechanically transmitted with up to 100% efficiency in melon. The physiological stage of the inoculated organ (cotyledon or leaf) represents a key factor for inoculation efficiency. This result provides a simple and reliable inoculation method to develop extensive screening for M e CMV resistance sources. In addition, the complex M e CMV  + Me CMA was mechanically transmitted to melon, N . benthamiana and N . clevelandii plantlets and successfully back‐transmitted. To the authors’ knowledge, this finding is the first evidence of sap transmission for a begomovirus–satellite complex.