Fusarium and Sarocladium Species Associated with Rice Sheath Rot Disease in Sub-Saharan Africa

Afolabi, O O and Bigirimana, V de P and Hua, G K H and Oni, F E and Bertier, L and Onwughalu, J and Oyetunji, O E and Ogunbayo, A and Velde, M V D and Nyamangyoku, O I and Saeger, S D and Höfte, M (2023) Fusarium and Sarocladium Species Associated with Rice Sheath Rot Disease in Sub-Saharan Africa. Diversity (TSI), 15 (10). pp. 1-22. ISSN 1424-2818

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Sarocladium and Fusarium species are commonly identified as causal agents of rice sheath rot disease worldwide. However, limited knowledge exists about their genetic, pathogenic, and toxigenic diversity in sub-Saharan African (SSA) countries, where an increasing incidence of this disease has been observed. In this study, seventy fungal isolates were obtained from rice plants displaying disease symptoms in rice research programs and farmer fields in Mali, Nigeria, and Rwanda. Thus, an extensive comparative analysis was conducted to assess their genetic, pathogenic, and toxigenic diversity. The Fusarium spp. were characterized using the translation elongation factor (EF-1a) region, while a concatenation of Internal Transcribed Spacer (ITS) and Actin-encoding regions were used to resolve Sarocladium species. Phylogenetic analysis revealed four Fusarium species complexes. The dominant complex in Nigeria was the Fusarium incarnatum-equiseti species complex (FIESC), comprising F. hainanense, F. sulawesiense, F. pernambucatum, and F. tanahbumbuense, while F. incarnatum was found in Rwanda. The Fusarium fujikuroi species complex (FFSC) was predominant in Rwanda and Mali, with species such as F. andiyazi, F. madaense, and F. casha in Rwanda and F. annulatum and F. nygamai in Mali. F. marum was found in Nigeria. Furthermore, Fusarium oxysporum species complex (FOSC) members, F. callistephi and F. triseptatum, were found in Rwanda and Mali, respectively. Two isolates of F. acasiae-mearnsii, belonging to the Fusarium sambucinum species complex (FSAMSC), were obtained in Rwanda. Isolates of Sarocladium, which were previously classified into three phylogenetic groups, were resolved into three species, which are attenuatum, oryzae, and sparsum. S. attenuatum was dominant in Rwanda, while S. oryzae and S. sparsum were found in Nigeria. Also, the susceptibility of FARO44, a rice cultivar released by Africa Rice Centre (AfricaRice), was tested against isolates from the four Fusarium species complexes and the three Sarocladium species. All isolates evaluated could induce typical sheath rot symptoms, albeit with varying disease development levels. In addition, liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to determine variation in the in vitro mycotoxins of the Fusarium species. Regional differences were observed in the in vitro mycotoxins profiling. Out of the forty-six isolates tested, nineteen were able to produce one to four mycotoxins. Notably, very high zearalenone (ZEN) production was specific to the two F. hainanense isolates from Ibadan, Nigeria, while Fusarium nygamai isolates from Mali produced high amounts of fumonisins. To the best of our knowledge, it seems that this study is the first to elucidate the genetic, pathogenic, and toxigenic diversity of Fusarium species associated with the rice sheath rot disease complex in selected countries in SSA.

Item Type: Article
Divisions: Research Program : West & Central Africa
Uncontrolled Keywords: pathogenic variability, genetic diversity, mycotoxins, Fusarium incarnatum-equiseti species complex (FIESC), Fusarium fujikuroi species complex (FFSC), Sarocladium attenuatum, Sarocladium oryzae, Sarocladium sparsum
Subjects: Others > Rice
Others > Plant Pathology
Depositing User: Mr Nagaraju T
Date Deposited: 20 Feb 2024 04:41
Last Modified: 20 Feb 2024 04:41
URI: http://oar.icrisat.org/id/eprint/12493
Official URL: https://www.mdpi.com/1424-2818/15/10/1090
Acknowledgement: The authors wish to appreciate Christ’l Detavernier, Frédéric Dumoulin (UGent, Faculty of Pharmaceutical Sciences) for their help with the LC-MS/MS analysis. We also acknowledged the contributions of Aderonke Oludare and Opeyemi Ogedengbe (AfricaRice) for their coordination of rice sampling and transportation to Belgium.
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