Virulence and toxin synthesis of an azole insensitive Fusarium culmorum strain in wheat cultivars with different levels of resistance to fusarium head blight

Abstract

Fusarium culmorum causes head blight, produces toxins and reduces yield and quality of cereals. To prevent damage caused by fusarium head blight (FHB), azole fungicides are mainly applied. The occurrence of insensitivity to azoles is a major problem in agriculture. The present study shows that a tebuconazole insensitive strain of F. culmorum can be readily produced in the laboratory, but that the resulting strain of the fungus is of lower fitness in vitro. Insensitivity was confirmed microscopically and by cell viability and metabolic activity. The tebuconazole insensitive strain shows cross insensitivity to nine important azoles. In addition, plants inoculated with the insensitive F. culmorum strain showed no reduction of FHB symptoms and deoxynivalenol (DON) content after tebuconazole treatment, compared to an inoculation with the sensitive strain. Use of wheat cultivars carrying a high resistance level (i.e. cv. Toras) was the most effective method for reducing symptoms and decreasing DON content, independent from the level of fungicide insensitivity of the F. culmorum strain. In conclusion, resistant cultivars and a fungicide mixture which combines different mechanisms of action in fungal metabolism should be applied to avoid fungicide insensitivity of Fusarium spp. in future.

FcRav2, a gene with a ROGDI domain involved in Fusarium head blight and crown rot on durum wheat caused by Fusarium culmorum

“…activity of known fungicides, as suggested previously for human fungal pathogens (Hayek et al, 2014). For this reason, we propose that RAV2 in F. graminearum and F. culmorum may represent a new target for the development of integrative approaches against fungicide adaptation and resistance, or low-sensitivity phenomena that are becoming important against different fungicides in Fusaria (Becher et al, 2011;Chen and Zhou, 2009;Dubos et al, 2011Dubos et al, , 2013Serfling and Ordon, 2014;Talas and McDonald, 2015). FcRav2 appears to be deeply involved in a number of morphological and physiological traits, but no definite phenotypes were identified in Candida albicans in a large genomic screening of mutants (Noble et al, 2010).…”

“…Provided that the RAV2 gene may be present only in fungi (Parra et al ., ), it appears now pivotal to focus on molecules able to interfere with RAV2 in planta in order to impair the toxigenic process, or to foster the activity of known fungicides, as suggested previously for human fungal pathogens (Hayek et al ., ). For this reason, we propose that RAV2 in F. graminearum and F. culmorum may represent a new target for the development of integrative approaches against fungicide adaptation and resistance, or low‐sensitivity phenomena that are becoming important against different fungicides in Fusaria (Becher et al ., ; Chen and Zhou, ; Dubos et al ., ; Serfling and Ordon, ; Talas and McDonald, ).…”

Is the emergence of fungal resistance to medical triazoles related to their use in the agroecosystems? A mini review

“… 9 , 23 The absence of ergosterol and the increase of intermediate compounds alter fungal membrane integrity as well as cell morphology, which inhibits fungal growth. 24 , 25 …”

Reduction of Fusarium head blight using prothioconazole and prothioconazole-tolerant variants of the Fusarium head blight antagonist Cryptococcus flavescens OH 182.9

“…Selected strains were tolerant to prothioconazole (Table 1) and at least one other triazole fungicide (tebuconazole, Schisler, unpublished). Cross insensitivity of Fusarium culmorum to multiple azoles has been reported (Serfling and Ordon, 2014). Antifungal drug resistance mechanisms include increased efflux, alteration of target enzyme or alteration of metabolism (Anderson, 2005).…”