Anouk C van Westerhoven, Harold J G Meijer, Joost Houdijk, Einar Martínez de la Parte, Elie Luntadila Matabuana, Michael F Seidl, Gert H J Kema.
Plant Dis.; 2023 Mar;107(3): 628-632. doi: 10.1094/PDIS-07-22-1576-SC.
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Abstract
Fusarium wilt of banana (FWB) is a serious soil-borne fungal disease. In the previous century, FWB already destroyed Gros Michel-based banana cultures in Central America, and currently, the disease threatens all major banana-producing regions of the world. The causal agents of these epidemics, however, are diverse. Gros Michel was infected by a wide range of Fusarium species, the so-called Race 1 strains, whereas the contemporary Cavendish-based cultures are affected by Fusarium odoratissimum, colloquially called Tropical Race 4 (TR4). TR4 was reported in Mozambique on two commercial banana farms in 2013, but no incursions were found outside the farm boundaries in 2015, suggesting that the disease was under control. Here we report the presence of TR4 outside of these farm boundaries. We obtained fungal samples from 13 banana plants in smallholder and roadside plantings at various locations throughout northern Mozambique. These samples tested positive for TR4 by molecular diagnostics and in greenhouse pathogenicity assays. The results were confirmed with reisolations, thereby completing Koch's postulates. To study the diversity of TR4 isolates in Mozambique, we selected five samples for whole-genome sequencing. Comparison with a global collection of TR4 samples revealed very little genetic variation, indicating that the fungus is clonally spreading in Mozambique. Furthermore, isolates from Mozambique are clearly genetically separated from other geographic incursions, and thus we cannot trace the origin of TR4 in Mozambique. Nevertheless, our data demonstrates the dissemination of TR4 in Mozambique, underscoring the failure of disease management strategies. This threatens African banana production.
See https://pubmed.ncbi.nlm.nih.gov/35984393/
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Fig. 2. Fusarium wilt of banana in Cavendish bananas in Mozambique is caused by Tropical Race 4 (TR4). A, TR4 diagnostic PCR results are positive (TR4 specific amplicon of 463 bp) on all monospore isolates, in duplicate, from five locations in Mozambique. B, TR4 diagnostic PCRs on all reisolated strains resulted in the TR4 diagnostic 463-bp amplicon. C, Greenhouse experiments showing Cavendish plants infected with TR4 isolates from Mozambique showing external and internal Fusarium wilt of banana symptoms. Controls in panels A, B, and C include Race 1 (negative), water (negative), and TR4 isolate II-5 (positive).
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