Abstract

RUIZ, Amy et al. Molecular Characterization and Pathogenicity Assays of Colletotrichum acutatum, Causal Agent for Lime Anthracnose in Texas. Rev. mex. fitopatol [online]. 2014, vol.32, n.1, pp.52-61. ISSN 2007-8080.

Several distorted Mexican lime [Citrus aurantiifolia (Christm). Swingle] fruit, leaf, and twig samples with lime anthracnose symptoms were collected from three trees in residential areas of Brownsville, Texas. The causal fungal organism, Colletotrichum acutatum J. H. Simmonds was isolated from leaves and fruit. Amplification of nuclear ribosomal DNA repeat region using ITS1 and ITS4 primers and intron 2 of the glyceraldehyde 3-phosphate dehydrogenase gene using GDF and GDR from fungal DNA resulted in approximately 520 bp and 260 bp amplicons, respectively. Similarity search for the nucleotide sequences obtained from 520 bp and 260 bp fragments at Basic Local Alignment Search Tool (BLASTn) program showed 99% identity to C. acutatum and 100% identity to several Colletotrichum species, respectively. The fungal isolates were further confirmed as C. acutatum by selective amplification of about 490 bp PCR fragment using species specific primer CaInt2 in combination with primer ITS4. Phylogenetic tree constructed using ITS nucleotide sequence data separated the isolate from the postbloom fruit drop (PFD) isolates and placed it in the group of key lime anthracnose (KLA) isolates. Pathogenicity assays by inoculation of detached leaves, flowers, and fruit showed that thornless Mexican lime and common Mexican lime showed typical symptoms of KLA while inoculated detached leaves of Rio Red grapefruit, Valencia sweet orange, Bearss lime, pink Eureka lemon, Eustis limequat, Ponderosa lemon, kaffir lime, seedless Lisbon lemon, and Meyer lemon did not develop any lesions.

Keywords : Key lime; anthracnose; Colletotrichum acutatum; citrus.

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