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Poster: Epidemiology: Pathogen Dispersal


First report of the Asian citrus psyllid, vector of Candidatus Liberibacter asiaticus in Tanzania and their potential further spread in Africa
M. SHIMWELA (1), H. Narouei-Khandan (1), S. Halbert (2), M. Keremane (3), G. Minsavage (1), S. Timilsina (1), D. Massawe (4), J. Jones (1), A. van Bruggen (1) (1) University of Florida, U.S.A.; (2) Division of Plant Industry, U.S.A.; (3) USDA, U.S.A.; (4)

Citrus surveys were conducted at high (>700m), medium (300-600m) and low (<200m) altitudes in Tanzania. Adults and nymphs of Trioza erytreae were abundant in the highlands and less abundant at medium altitudes. Unexpectedly, adults and nymphs of Diaphorina citri, the Asian citrus psyllid, were found at medium altitudes, around Morogoro. No psyllids were observed at low altitudes. Severe huanglongbing symptoms and tree decline were evident at high altitudes, while mild symptoms were observed at intermediate and low altitudes. DNA was extracted from leaf and psyllid samples and subjected to conventional PCR with seven different primer sets and qPCR with two primer sets for Candidatus Liberibacter spp. PCR products were sequenced and subjected to phylogenetic analysis. C. Liberibacter africanus (Laf) was detected in leaf and T. erytreae samples from high and medium altitudes by all methods. Sequences of C. Liberibacter DNA from leaves and psyllids were similar to those of Laf from South Africa. Even though Las primers gave a positive reaction in qPCR with medium altitude leaf samples, cPCR and sequencing results were negative for Las, suggesting cross reactivity of Las primers with Laf. Neither Laf nor Las were detected in D. citri samples. This is the first report of D. citri in Africa. Further surveys are needed to detect Las. The potential distribution of D. citri and Las in Africa was predicted using the correlative models MAXENT and Multi-Model Framework.