A Melon necrotic spot virus Untranslated RNA Sequence Is the Genetic Avirulence Determinant for Both Cultivar and Non-host Resistances

摘要

Melon necrotic spot virus-264 (MNSV-264) is able to overcome the resistance of melon (Cucumis melo L.) to MNSV. Construction of chi-meric mutants between MNSV-264 and MNSV-Moc5 (a non resistance-breaking isolate), generated through the exchange of the complete or parts of their 3'-ends using full length infectious cDNA clones, showed that the MNSV avirulence determinant resides in less than 50 nucleotides of the 3'-end. Site-directed mutagenesis showed that the RNA sequence itself gives this virus strain its resistance breaking ability. Additionally the 3'-UTR of MNSV-264 has been shown to contain the determinant for the unique ability of this isolate to infect Nicotiana benthamiana and Gomphrena globosa plants, normally non-host species for MNSV.