Resistance of Capsicum annuum 'Avelar' to pepper mottle potyvirus and alleviation of this resistance by co-infection with cucumber mosaic cucumovirusare associated with virus movement

Capsicum annuum cv, Avelar plants resist systemic infection by the Florida isolate of pepper mottle potyvirus (PepMoV-FL), Immune-tissue blot analysis for detection of PepMoV-FL infection in selected stem segments revealed th at virus moved down the stem in external phloem, and, over time, accumulate d to detectable levels throughout stem sections (appearing to accumulate in external and internal phloem) taken from below the inoculated leaf, At 21 days post-inoculation, PepMoV-FL was detected in stem segments one or two i nternodes above the inoculated leaf; however, no virus was observed in inte rnal phloem in stem segments beyond these internodes. In contrast to these observations, PepMoV-FL was detected in the internal phloem of all internod es of the stem located above the inoculated leaf, with subsequent movement into non-inoculated leaves, in Avelar plants co-infected with PepMoV-FL and cucumber mosaic cucumovirus (CMV-KM), No apparent enhancement of PepMoV-FL accumulation occurred in protoplasts inoculated with PepMoV-FL alone versu s a mixed inoculum of PepMoV-FL and CMV-KM, These findings confirm earlier observations that potyvirus movement up the stem of Capsicum species occurs via internal phloem. It is also shown that PepMoV-FL does not accumulate t o detectable levers in internal phloem in the stem of Avelar plants, thereb y limiting its movement to within the inoculated leaf and lower portions of the stem; however, co-infection of Avelar plants with CMV-KM alleviates th is restricted movement, allowing PepMoV-FL to invade young tissues systemic ally.