Submitted to: Plant Disease
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/12/2006
Publication Date: 5/1/2006
Citation: Irish, B.M., Goenaga, R.J., and Ploetz, R.C. 2006. Mycosphaerella fijiensis, Causal Agent of Black Sigatoka of Musa spp. found in Puerto Rico and Identified by Polymerase Chain Reaction. Plant Disease 90:684. Interpretive Summary: Black sigatoka is the most significant disease of bananas and plantains (Musa spp.). Most of the economically important cultivars of the exported and staple commodities are highly susceptible to this disease. Black sigatoka has not reportedly become wide spread in the Caribbean and has not been reported in Puerto Rico. In August 2004, symptoms resembling black sigatoka were first observed in Añasco, Puerto Rico by Extension personnel from the University of Puerto Rico. Black sigatoka is difficult to identify solely on symptoms. Consequently, a collection of isolates was assembled to confirm the presence of black sigatoka via a DNA diagnostic technique. Six DNA samples were positively identified as M. fijiensis the causal agent of black sigatoka. The presence of black sigatoka in Puerto Rico will most likely increase production costs and could be particularly problematic for small production farms, where fungicide applications will be needed in order to maintain yields. The USDA-ARS, Tropical Agriculture Research Station is the official Musa spp. germplasm repository for the National Plant Germplasm System. As such, efforts are underway to evaluate black sigatoka disease-resistant clones in our existing collection in addition to introduce any promising disease resistant material in the future which could satisfy local and export market criteria. Post-evaluation, disease resistant material could be distributed locally and regionally.
Technical Abstract: Black sigatoka, also known as black leaf streak, is caused by Mycosphaerella fijiensis Morelet (anamorph: Pseudocercospora fijiensis (Morelet) Deighton). It is the most significant disease of bananas and plantains (Musa spp.), and most of the economically important cultivars of these export and staple commodities are highly susceptible. The Caribbean is one of the few regions of the world where black sigatoka is not widespread. Black sigaoka has been reported in the Bahamas, Cuba, Hispaniola and Jamaica (1). Yellow sigatoka, caused by M. musicola Leach (anamorph: P. musae (Zimm.) Deighton), has been recognized in Puerto Rico since 1938-1939 (2). In August, 2004, symptoms of what appeared to be black sigatoka were first observed in Añasco, Puerto Rico by Extension personnel from the University of Puerto Rico. Since black and yellow sigatoka produce similar disease symptoms, a survey was conducted in the western banana and plantain production region of Puerto Rico, to confirm the presence of black sigatoka. Disease leaf samples of sigatoka infected plants were collected from production fields close to the towns of Las Marias, Maricao and Añasco. Single ascospore isolates of the teleomorphic stage were recovered using the discharge technique from moistened pseudothecia in necrotic lesions that were inverted over water agar. Single ascospore isolates were established and transferred to PDA. The isolates were sub-cultured in PDA broth for mycelium production. DNA was extracted from mycelium using a FastDNA® kit (Q-Biogen, Irvine, CA) for 29 isolates. Internal Transcribed Spacer (ITS) regions were PCR amplified with primers specific to M. fijiensis and M. musicola (3). Amplification products (~1100 bp) were observed for 18 of the 29 isolates, six of which were M. fijiensis and the remaining 12 were M. musicola; positive controls for both species also amplified. The source of M. fijiensis in Puerto Rico is unclear, but it may have originated from leaf material and/or traditional seed pieces (rhizomes) introduced from neighboring countries. The presence of black sigatoka in Puerto Rico will most likely increase production costs, where fungicide applications will be needed in order to maintain yields. The USDA-ARS, Tropical Agriculture Research Station is the official Musa spp. germplasm repository for the National Plant Germplasm System. As such, efforts are underway to introduce and evaluate black sigatoka disease-resistant clones that can satisfy local and export market criteria.