Abstract Triazole fungicides are used broadly for the control of infectious diseases of both humans and plants. The surge in resistance to triazoles among pathogenic populations is an emergent issue both in agriculture and medicine. The non-rational use of fungicides with site-specific modes of action, such as the triazoles, may increase the risk of antifungal resistance development. In the medical field, the surge of resistant fungal isolates has been related to the intensive and recurrent therapeutic use of a limited number of triazoles for the treatment and prophylaxis of many mycoses. Similarities in the mode of action of triazole fungicides used in these two fields may lead to cross-resistance, thus expanding the spectrum of resistance to multiple fungicides and contributing to the perpetuation of resistant strains in the environment. The emergence of fungicide-resistant isolates of human pathogens has been related to the exposure to fungicides used in agroecosystems. Examples include species of cosmopolitan occurrence, such as Fusarium and Aspergillus, which cause diseases in both plants and humans. This review summarizes the information about the most important triazole fungicides that are largely used in human clinical therapy and agriculture. We aim to discuss the issues related to fungicide resistance and the recommended strategies for preventing the emergence of triazole-resistant fungal populations capable of spreading across environments.

No Brasil, a giberela em trigo é causada por espécies do complexo Fusarium graminearum, especialmente F. graminearum sensu stricto (Fgss) e F. meridionale (Fmer), as quais variam quanto ao potencial toxigênico. O objetivo deste trabalho foi avaliar a relação entre características fenotípicas e agressividade dessas duas espécies associadas ao uso do fungicida tebuconazole, da classe dos triazóis, com a redução de rendimento do trigo. Em dez isolados Fgss e nove Fmer, foram avaliados: esporulação total, taxa de germinação e sensibilidade ao fungicida tebuconazole. A inoculação, para cada isolado, foi feita por aspersão em espigas e as variáveis severidade da doença, incidência de grãos giberelados e o peso de grãos foram avaliados. O efeito de tebuconazole na redução da doença foi avaliado em ação protetora, seguida de inoculação na espigueta central de plantas da cultivar 'BRS Guamirim', com os seguintes tipos de inóculo: somente Fgss, somente Fmer ou a mistura de ambos (1:1). Isolados Fgss apresentaram maior esporulação total, maior taxa de germinação e foram menos sensíveis ao tebuconazole em comparação a Fmer. Grãos giberelados por isolados Fmer apresentaram 50% maior peso do que aqueles provenientes de inoculações com Fgss. O tebuconazole apresentou efeito fungistático e os grãos de espigas tratadas com o fungicida apresentaram peso 25% superior aos não tratados. Sugere-se que diferenças no potencial de dano aos grãos pelas duas espécies, assim como o efeito fungistático de triazóis, podem ajudar a explicar a co-ocorrência de diferentes micotoxinas, o que ainda necessita ser confirmado com dados de campo.

Fusarium head blight of wheat in Brazil is caused mainly by two species of the Fusarium graminearum species complex: F. graminearum sensu stricto (Fgss) and F. meridionale (Fmer), which vary in relation to toxigenic potential. The aim of this study was to evaluate the effect of phenotypic traits and aggressiveness of these two species, associated with the tebuconazole fungicide, of the triazole group, on the reduction of wheat yield. Ten Fgss strains and Fmer strains were evaluated with regards to: total sporulation, germination rate and tebuconazole sensitivity. The strains were spray-inoculated onto BRS Guamirim cv. 'plants' at full flowering and disease severity, Fusarium-damaged kernels, and kernel weight were evaluated. The effect of tebuconazole in disease control was evaluated through spraying the fungicide and then inoculating the central-floret of the wheat head with the following inoculum treatments: a mixture of all Fgss strains, a mixture of all Fmer strains or a mixture of all isolates of both species (1:1). Strains of Fgss showed higher total sporulation and germination rates and were less sensitivity to tebuconazole. The weight of Fusarium-damaged kernels from inoculations with Fmer strains was 50% higher than those inoculated with Fgss. A fungistatic effect on the disease was found for tebuconazole application and harvested kernels showed 25% higher grain weight than the untreated kernels. It is suggested that the distinct yield loss potential by these two species, in association with the fungistatic effect of triazoles could explain the co-occurrence of different mycotoxins in the harvested kernels, which needs to be proven with field data.

No Brasil, diversas espécies de Fusarium são patogênicas ao milho, afetando sementes, plântulas, colmos e grãos. Objetivou-se comparar isolados de F. verticillioides e de duas espécies do complexo F. graminearum (F. graminearum sensu stricto e F. meridionale), de ocorrência predominante em sementes de milho, quanto à taxa de crescimento micelial, capacidade de colonização e redução da germinação da semente, redução da emergência de plântulas e infecção e colonização de colmos de milho.Testes permutacionais e análise de contraste foram usados para discriminar os isolados. Análise de componentes principais foi utilizada para identificar as variáveis responsáveis pela maior variância entre os isolados. Com exceção da redução da germinação, os isolados F. verticillioides apresentaram menores valores de taxa de crescimento micelial, eficiência de infecção, redução na emergência de plântulas e comprimento de lesão em colmos, quando comparados aos demais, que não se diferenciaram. As variáveis redução da emergência e redução da germinação apresentaram maior influência na caracterização dos isolados, sugerindo que sementes infectadas com isolados de qualquer uma das espécies do complexo F. graminearum testadas representam maior risco ao estabelecimento da cultura do que isolados de F. verticillioides.

In Brazil, several Fusarium species are pathogenic to corn affecting seeds, seedlings, stalks and grains. This research aimed to compare isolates from F. verticillioides and from two species of the F. graminearum complex (F. graminearum sensu stricto and F. meridionale) prevalent on corn seeds in relation to mycelial growth rate, ability to colonize and reduce seed germination, reduction in seedling emergence and infection and colonization of corn stalk. Permutational test and contrast analysis was performed to discriminate the isolates and species. Principal component analysis was used to identify the variables leading to greatest variance among the isolates. With the exception of seed germination, F. verticillioides isolates showed lower values for mycelial growth rate, infection efficiency, reduction in seedling emergence and lesion size than F. graminearum complex isolates that were all similar. Seedling emergence and seed germination showed greater influence on the characterization of isolates, suggesting that seeds infected with F. graminearum isolates of any of the species tested represent a greater threat to crop stand than F. verticillioides isolates.

Fusarium head blight (FHB) of wheat, is caused by fungal populations belonging to the Fusarium graminearum species complex. Although triazole fungicides are widely used in FHB management, information about the sensitivity of F. graminearum populations to such fungicides is scarce, particularly in Brazil. This work aimed at determining the sensitivity of pathogenic populations of F. graminearum to metconazole and tebuconazole. Fungal isolates were obtained from diseased wheat heads collected in commercial fields at the northern region of Rio Grande do Sul state, Brazil, along the 2009 and 2010 growing seasons. Fifty isolates obtained from eleven locations were grown in media amended with increasing fungicide dosages and the effective concentration reducing mycelial growth to 50% (EC50) was determined. The median of the EC50 values was 0.001 mg/L (<0.001-0.152 mg/L) and 0.037 mg/L (<0.001-0.324), for tebuconazole and metconazole, respectively. Cross-resistance was detected based on significance of correlation analysis (r s = 0.46; P < 0.0001) between the log-transformed EC50 of the two triazoles. The mean EC50 for a group of ten isolates classified as "more sensitive" differed statistically from the ten isolates representing the "less sensitive" group. Nevertheless, these groups did not differ in terms of mycelial growth on PDA in the absence of fungicides. It was concluded that pathogenic populations of F. graminearum are sensitive to the triazoles at various levels due to the intrinsic characteristics of the isolates or to selection pressure by the increasing fungicide use.