Multi-site fungicides suppress banana Panama disease, caused by Fusarium oxysporum f. sp. cubense Tropical Race 4

Abstract

Global banana production is currently challenged by Panama disease, caused by Fusarium oxysporum f.sp. cubense Tropical Race 4 (FocTR4). There are no effective fungicide-based strategies to control this soil-borne pathogen. This could be due to insensitivity of the pathogen to fungicides and/or soil application per se. Here, we test the effect of 12 single-site and 9 multi-site fungicides against FocTR4 and Foc Race1 (FocR1) in quantitative colony growth, and cell survival assays in purified FocTR4 macroconidia, microconidia and chlamydospores. We demonstrate that these FocTR4 morphotypes all cause Panama disease in bananas. These experiments reveal innate resistance of FocTR4 to all single-site fungicides, with neither azoles, nor succinate dehydrogenase inhibitors (SDHIs), strobilurins or benzimidazoles killing these spore forms. We show in fungicide-treated hyphae that this innate resistance occurs in a subpopulation of "persister" cells and is not genetically inherited. FocTR4 persisters respond to 3 μg ml-1 azoles or 1000 μg ml-1 strobilurins or SDHIs by strong up-regulation of genes encoding target enzymes (up to 660-fold), genes for putative efflux pumps and transporters (up to 230-fold) and xenobiotic detoxification enzymes (up to 200-fold). Comparison of gene expression in FocTR4 and Zymoseptoria tritici, grown under identical conditions, reveals that this response is only observed in FocTR4. In contrast, FocTR4 shows little innate resistance to most multi-site fungicides. However, quantitative virulence assays, in soil-grown bananas, reveals that only captan (20 μg ml-1) and all lipophilic cations (200 μg ml-1) suppress Panama disease effectively. These fungicides could help protect bananas from future yield losses by FocTR4.

Effects of Chemical and Biological Fungicide Applications on Sexual Sporulation of Rhizoctonia solani AG-3 TB on Tobacco

“…At the same time, the results of this study perfectly explain the phenomenon in which tobacco farmers often use elevated concentrations and extreme doses of fungicides to cause outbreaks of disease in tobacco fields. It is worth noting that propiconazole, carbendazim, thiophanate and mancozeb are now banned in EU countries [ 47 , 48 ], but they are the most widely used fungicides and insecticides in China, and they are still the main products for farmers to protect crops [ 49 , 50 ]. It is well known that propiconazole-morpholine guanidine is a wettable powder with the following active ingredients and their concentrations: morpholine guanidine 16%, and propiconazole 2%.…”

Antifungal effects and biocontrol potential of lipopeptide-producing Streptomyces against banana Fusarium wilt fungus Fusarium oxysporum f. sp. cubense

“…In spite of this, no commercial varieties that are fully Foc TR4-resistant are yet available ( Damodaran et al, 2020 ). Soil fumigation using chemical fungicides (e.g., carbendazim) is a conventional agronomic practice to control soil-borne pathogens, but their extended use has raised environmental, economic and safety concerns, and has occasionally led to the emergence of fungicide resistance ( Getha and Vikineswary, 2002 ; Cannon et al, 2022 ). While crop rotation can effectively reduce FWB incidence ( Wang et al, 2015 ; Fan et al, 2022 ), this method is not always practical for large-scale banana plantations due to the extended period of time it requires.…”

Azoles activate type I and type II programmed cell death pathways in crop pathogenic fungi

“…Sensitivity of Z. tritici IPO323 to azoles was determined as described previously 71 . In brief, YPD agar plates were supplemented with various azole concentrations.…”