Resistência a benzimidazóis por Guignardia citricarpa

Abstract

Resumo -O objetivo deste trabalho foi avaliar a resistência de Guignardia citricarpa aos fungicidas carbendazim e piraclostrobina, por meio de avaliação do crescimento em meio de cultura, decomposição de tecido foliar e produção de corpos de frutificação. Para isso, o fungo G. citricarpa foi isolado de lesões de frutos de laranja (Citrus sinensis), produzidos em área com intensa aplicação de fungicida. Os isolados obtidos foram avaliados quanto à sensibilidade aos fungicidas piraclostrobina e carbendazim, nas dosagens de 0,5, 1 e 2 µg mL -1 de i.a., para se verificar o efeito da pressão de seleção causada pelo uso destes compostos em áreas citrícolas. Embora tenha sido observada redução efetiva no número de estruturas reprodutivas e na decomposição de folhas e frutos infectados com G. citricarpa, após a aplicação dos fungicidas, 7,5% dos isolados avaliados sobre meio de cultura apresentaram resistência a esse fungicida, o que indica que pode ocorrer seleção de isolados resistentes no campo. Para a piraclostrobina não foi observada resistência, o que indica que pode ser um composto alternativo para ser utilizado de forma alternada com carbendazim, para diminuir as chances de ocorrência de resistência do patógeno.Termos para indexação: mancha-preta dos citros, pinta-preta, tolerância a fungicidas, citricultura. Guignardia citricarpa resistance to benzimidazolesAbstract -The objective of this work was to evaluate the resistance of Guignardia citricarpa to pyraclostrobine and carbendazim fungicides, through: growth analysis in culture media amended with the fungicides; leaf decomposition; and production of reproductive structures on leaves naturally infected with these fungi. G. citricarpa was isolated from symptomatic fruits of sweet orange (Citrus sinensis) cultivated in area with intense fungicide application. The sensibility to fungicides of G. citricarpa isolates was evaluated with pyraclostrobine and carbendazim, in the doses 0.5, 1 e 2 µg mL -1 a.i., to verify the effect of selection pressure caused by continuous use of these compounds. Although, reduction on leaf decomposition and on the number of reproductive structures were observed after application of pyraclostrobine and carbendazim, 7.5% of the isolates, evaluated in culture media, exhibited resistance to carbendazim, suggesting that the use of this agrochemical must be combined to other active principles in a consortium to reduce the chances of resistance occurrence. No resistance to pyraclostrobine was observed among tested isolates, what indicates that this could be an alternative compound to be used in combination to carbendazim, to minimize the chance of resistance occurrence.Index terms: citrus black-spot, fungicide resistance, citriculture. IntroduçãoA mancha-preta dos citros (MPC), cujo agente causal é o fungo Guignardia citricarpa Kiely (anamorfo Phyllosticta citricarpa McAlpine 1973), é caracterizada por lesões na casca de frutos de laranjas doces, limões, tangerinas e seus híbridos, o que os torna depreciados para o mercado de fruta fresca. Q...

Reaction of hybrids, inhibition in vitro and target spot control in cucumber

“…Thiophanate-methyl, also from the benzimidales chemical group, acts by interfering in the DNA synthesis or with the cell or nuclear division process (Picinini, 1994). Several recent studies carried out in Brazil with other pathosystems such as Didymella bryoniae-watermelon where isolates were detected with crossed resistance to thiophanate-methyl and carbendazin (Santos et al, 2006); Guignardia citricarpa-citrus where selection pressure was tested using benzimidales fungicides in the citrus producing regions (Rodrigues et al, 2007) and Lasiodiplodia theobromaep a p a y a , w h e r e h i g h e s t i m a t e d ED 50 values were observed for all the fungicides tested, especially the benzimidales, that indicated selection pressure in the field resulting from the intensive use of this fungicide (Pereira, 2009).…”

Reduction in the in vitro sensitivity oF Drechslera tritici-repentis, isolated from wheat, to strobilurin and triazole fungicides

“…Rodrigues et al (24) argued that, for strobilurins, there may be cross-resistance to azoxystrobin, pyraclostrobin and trifloxystrobin. Nevertheless, we do not have any explanation for the performance of pyraclostrobin, the most efficient fungicide for spore germination inhibition.…”

“…Os dados da porcentagem da inibição da Tonin, R. B; Reis, E. M.; Avozani, A. Redução da sensibilidade in vitro de Drechslera tritici-repentis, isolados do trigo, a fungicidas estrobilurinas e triazóis, in vitro. Summa Phytopathologica, v.43, n.1, p. [20][21][22][23][24][25]2017. The fungus Pyrenophora tritici-repentis (Died.)…”

Fungicide resistance and genetic variability in plant pathogenic strains of Guignardia citricarpa

“…In Brazil, Martins et al 1998 (18) published the first case of G. citricarpa resistance to benomyl in citrus plants. In addition, isolates of G. citricarpa from lesions on Citrus sinensis fruits exhibited resistance to different concentrations of carbendazim, also a fungicide of the benzimidazole group (23).…”