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Poster: Epidemiology: Pathogen Dispersal


The seasonal dynamics of Phyllosticta spp. in Floridian citrus grove leaf litter
K. ZHANG (1), J. Rollins (2), M. Dewdney (3) (1) Plant Pathology Department, Citrus Research and Education Center, University of Florida, U.S.A.; (2) Plant Pathology Department, University of Florida, U.S.A.; (3) Plant Pathology Department, Citrus Researc

The causal agent of Citrus Black Spot (CBS), Phyllosticta citricarpa, is a restricted pathogen in Europe and quarantined in the US after it was found in Florida in 2010. Additionally, an endophytic fungus P. capitalensis, associated with a wide range of hosts including citrus, is globally distributed and commonly found in Floridian citrus. These two species cannot be distinguished morphologically; therefore, previous CBS epidemiology studies included both endophyte and pathogen. Both fungi overwinter and produce ascospores and conidia in leaf litter. Understanding the seasonal dynamics of these two species in leaf litter can provide knowledge to control CBS inoculum in Floridian groves. 1000 leaves were collected biweekly from 40 arbitrarily selected trees in a grove in south Florida since May 2014. The number of leaves with fructifications, the number of Phyllosticta spores collected from the leaf litter, and the average leaf degradation level from each sample were recorded. The quantity of P. citricarpa and P. capitalensis DNA in leaf litter and spore suspensions was determined via qPCR. The results showed that the fructification abundance is correlated with leaf degradation level (pseudothecium: P = 0.0008, pycnidium: P = 0.0333), conidia were always present, and ascospores were occasionally absent. The quantity of P. capitalensis DNA was constant while the quantity of P. citricarpa DNA increased throughout the two-year sample collection period.