ENHANCED COMPETITIVENESS OF TOMATO BUSHY STUNT VIRUS DEFECTIVE INTERFERING RNAS BY SEGMENT DUPLICATION OR NUCLEOTIDE INSERTION

We have analyzed atypical tomato bushy stunt virus defective interferi ng (DI) RNA species which accumulated during a passage series in proto plasts. We present a rationale for the order of appearance of these mo lecules and show, using competition assays, that either segment duplic ation or single nucleotide insertion caa enhance DI RNA competitivenes s. Possible mechanisms for the introduction of the modifications obser ved in these DI RNAs are discussed.