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2018-04-26T22:00:00.0000000Z
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New Geographical Insights of the Latest Expansion of Fusarium oxysporum f.sp. cubense Tropical Race 4 Into the Greater Mekong Subregion

https://www.frontiersin.org/articles/10.3389/fpls.2018.00457/full

Plant Sci., 09 April 2018 | https://doi.org/10.3389/fpls.2018.00457

Si-Jun Zheng1,2*†, Fernando A. García-Bastidas3,4†, Xundong Li1†, Li Zeng1, Tingting Bai1, Shengtao Xu1, Kesuo Yin1, Hongxiang Li5, Gang Fu6, Yanchun Yu7, Liu Yang8, Huy Chung Nguyen9, Bounneuang Douangboupha10, Aye Aye Khaing11, Andre Drenth12, Michael F. Seidl4, Harold J. G. Meijer3 and Gert H. J. Kema3,4*
1Agricultural Environment and Resources Institute, Yunnan Academy of Agricultural Sciences, Kunming, China
2Bioversity International, Kunming, China
3Wageningen University and Research, Wageningen Plant Research, Wageningen, Netherlands
4Wageningen University and Research, Laboratory of Phytopathology, Wageningen, Netherlands
5Xishuangbanna Dai Autonomous Prefecture, Plant Quarantine and Protection Station, Jinghong, China
6Institute of Microbiology, Guangxi Academy of Agricultural Sciences, Nanning, China
7Institute of Tropical and Subtropical Industry Crops, Yunnan Academy of Agricultural Sciences, Kunming, China
8Institute of Biotechnology, Guangxi Academy of Agricultural Sciences, Nanning, China
9Plant Protection Research Institute, Vietnam Academy of Agricultural Sciences, Hanoi, Vietnam
10Ministry of Agriculture & Forestry, National Agriculture & Forestry Research Institute, Horticulture Research Center, Vientiane, Laos
11Biotechnology Research Department, Mandalay, Myanmar
12Centre for Horticultural Science, The University of Queensland, Brisbane, QLD, Australia
    Banana is the most popular and most exported fruit and also a major food crop for millions of people around the world. Despite its importance and the presence of serious disease threats, research into this crop is limited. One of those is Panama disease or Fusarium wilt. In the previous century Fusarium wilt wiped out the “Gros Michel” based banana industry in Central America. The epidemic was eventually quenched by planting “Cavendish” bananas. However, 50 years ago the disease recurred, but now on “Cavendish” bananas. Since then the disease has spread across South-East Asia, to the Middle-East and the Indian subcontinent and leaped into Africa. Here, we report the presence of Fusarium oxysporum f.sp. cubense Tropical Race 4 (Foc TR4) in “Cavendish” plantations in Laos, Myanmar, and Vietnam. A combination of classical morphology, DNA sequencing, and phenotyping assays revealed a very close relationship between the Foc TR4 strains in the entire Greater Mekong Subregion (GMS), which is increasingly prone to intensive banana production. Analyses of single-nucleotide polymorphisms enabled us to initiate a phylogeography of Foc TR4 across three geographical areas—GMS, Indian subcontinent, and the Middle East revealing three distinct Foc TR4 sub-lineages. Collectively, our data place these new incursions in a broader agroecological context and underscore the need for awareness campaigns and the implementation of validated quarantine measures to prevent further international dissemination of Foc TR4.

Introduction

    Panama disease or Fusarium wilt is caused by the soil-borne fungus Fusarium oxysporum f.sp. cubense (Foc), and was first described in Australia in 1874 (Bancroft, 1876). The fungus penetrates the roots and from there colonizes the vascular system of the banana plant. Together with the plant responses, this results in occlusion of the xylem vessels which causes wilting and eventually death of infected plants (Guo et al., 2014). The decimation of susceptible “Gros Michel” bananas that were grown in large-scale monoculture plantations in Central America during the 1900s earned Fusarium wilt its reputation as a pathogen of global significance. Losses of “Gros Michel” were first recognized in Central America (Costa Rica and Panama) in 1890, and were soon reported in Africa, the Caribbean, and South America (Ploetz, 2015). The Fusarium wilt epidemic was caused by a set of Foc strains that are collectively called Race 1 and decimated the large-scale monocultures of “Gros Michel” on which the banana industry in America relied. No effective control methods were found other than replacing “Gros Michel” with resistant “Cavendish” bananas in Central America during the 1960s. This replacement has been highly successful to quench the Fusarium wilt epidemic that was caused by Foc Race 1 strains. Since then, “Cavendish” production expanded into large global monocultures, which are evidently prone to disease threats, including black Sigatoka and Panama disease (Ordoñez et al., 2015b; Arango Isaza et al., 2016; Diaz-Trujillo et al., 2018).  Read on...

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