Pathogenicity Regulation by Satellite RNAs of Cucumber Mosaic Virus: Minor Nucleotide Sequence Changes Alter Host Responses. Peter Palukaitis. Department of Plant Pathology, Cornell University, Ithaca, NY 14853 U.S.A.. . MPMI 1:175-181. Accepted 12 May 1988. Copyright 1988 The American Phytopathological Society.

Six satellite RNAs of cucumber mosaic virus (CMV) could be differentiated on the basis of symptom expression they elicit in tomato and tobacco, and all but two could be differentiated by gel electrophoretic migration. Three of the satellite RNAs (B₂-sat, G-sat, and WL₁-sat RNA) ameliorated the symptoms induced by CMV on tomato, whereas three others (B₁-sat, and B₃-sat, and WL₂-sat RNA) induced chlorosis on tomato, the extent and nature of which was CMV-strain dependent. By contrast, B₂-sat RNA induced cholorosis in tobacco, whereas WL₁-sat and G-sat RNAs did not. Thus, the symptoms observed were dependent on the host species, the particular satellite RNA, and also the strain of helper virus, suggesting that a complex association of at least three factors is involved in symptom elicitation. Comparisons of the nucleotide sequences of pairs of satellite RNAs inducing the various chlorotic responses suggest that only a few nucleotide changes in specific domains are required for the elicitation of different host responses.