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Poster: Biology & Disease Mgmt: Mycology


Genetic characterization of the Colletotrichum gloeosporioides complex in apple orchards of North Carolina
B. HOGE (1), M. Cubeta (1), D. Ritchie (1) (1) North Carolina State University, U.S.A.

Glomerella leaf spot caused by fungi in the Colletotrichum gloeosporioides (Cg) species complex is an important disease of apple (Malus domestica). It is associated with leaf and fruit spots, resulting in yield loss and premature defoliation of trees. While several studies have characterized the genotypic diversity of species complexes within Colletotrichum, little information is available on pathogen diversity on apple cultivars in North Carolina (NC). Development of sustainable management strategies requires consideration of both host and pathogen factors and information on their association with disease incidence and severity. The primary objective of this study was to examine the genetic diversity of field populations of Cg sampled from infected fruits and leaves of cultivars Gala, Golden Delicious, Pink Lady, Granny Smith, and Yellow Transparent in 15 orchards in NC. Genomic DNA was extracted from a phenotypically diverse subsample (n=50) of 150 isolates and sequence analysis of four independent genetic loci was performed to identify multi-locus haplotypes (MLHs). Eight distinct MLHs were detected, and three well-supported lineages corresponding to species in the Cg complex were identified. Isolates identified as MLH1 belonged to the Cg clade and were sampled from three of five cultivars. MLH2 isolates were identified as C. fructicola, and sampled from four of five cultivars with some overlap. The remaining MLHs were restricted to a single cultivar or isolate.