Poster: Late and Moved Abstracts
Abs #
1027: Distribution of Xanthomonas campestris pv. pelargonii after leaf surface inoculation of geranium.
Known quantities of a rifampicin resistant strain of Xanthomonas campestris pv. pelargonii (Xcp) were inoculated to either the leaf surface or cut petiole of geraniums (Pelargonium spp.). Plants were incubated for 8 weeks in a growth chamber under conditions conducive for bacterial replication and symptom development for bacterial wilt disease. Inoculated and non-inoculated leaves were then collected, and extracts were plated for viability testing on YDC agar containing rifampicin. Likewise, plant tissues were extracted and underwent PCR amplification using previously described primer pairs specific for Xcp DNA and for the geranium 18s rRNA gene. Plants on which Xcp was inoculated to the leaf surface appeared healthy throughout the 8 week incubation. Viability testing showed no significant spread of Xcp from initially inoculated leaves, and PCR analysis showed no detectable movement of Xcp from inoculated leaves. Mock inoculated plants continued to appear healthy and yielded no detectable Xcp by either viability testing or PCR. Control plants that were petiole inoculated with Xcp showed systemic symptoms and Xcp was shown to be widely distributed, both by viability testing and by PCR. These results suggest that even under optimum conditions for bacterial replication and movement, the mere presence of Xcp on the phylloplane does not necessarily portend that the bacteria will gain entry into the plant to reproduce or to cause disease.
