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Molecular Diagnostics for the Sigatoka Disease Complex of Banana

First and eighth authors: Laboratory of Phytopathology, Wageningen University, Binnenhaven 5, 6709 PD Wageningen, The Netherlands; first, second, and eighth authors: CBS Fungal Biodiversity Centre, Uppsalalaan 8, 3584 CT Utrecht, The Netherlands; third, fourth, and sixth authors: Plant Research International BV, P.O. Box 16, 6700 AA Wageningen, The Netherlands; fifth author: Centre de Coopération Internationale en Recherche Agronomique pour le Développement (CIRAD), UMR-BGPI, TA41/K, Campus International de Baillarguet 34398 Montpellier Cedex 5, France; and seventh author: CORBANA S.A., P.O. Box 6504-1000 San José, Costa Rica.

The Sigatoka disease complex of banana involves three related ascomycetous fungi, Mycosphaerella fijiensis, M. musicola, and M. eumusae. The exact distribution of these three species and their disease epidemiology remain unclear, because their symptoms and life cycles are rather similar. Disease diagnosis in the Mycosphaerella complex of banana is based on the presence of host symptoms and fungal fruiting structures, which hamper preventive management strategies. In the present study, we have developed rapid and robust species-specific molecular-based diagnostic tools for detection and quantification of M. fijiensis, M. musicola, and M. eumusae. Conventional species-specific polymerase chain reaction (PCR) primers were developed based on the actin gene that detected DNA at as little as 100, 1, and 10 pg/μl from M. fijiensis, M. musicola, and M. eumusae, respectively. Furthermore, TaqMan real-time quantitative PCR assays were developed based on the β-tubulin gene and detected quantities of DNA as low as 1 pg/μl for each Mycosphaerella sp. from pure cultures and DNA at 1.6 pg/μl per milligram of dry leaf tissue for M. fijiensis that was validated using naturally infected banana leaves.

Additional keywords: Mycosphaerella spp., Sigatoka complex.