-The objective of this work was to evaluate the effect of phosphites in the protection of common bean (Phaseolus vulgaris) against anthracnose. Different phosphite formulations were evaluated by quantifying peroxidase and polyphenol oxidase activity, total phenols, and lignin content. The treatments consisted of sprayings, in the V4, R5, and R7 stages, with: the K, Zn, Mn, K+Mn, K+salicyclic acid, and Cu phosphites; salicylic acid; acibenzolar-S-methyl; the fungicide azoxystrobin; besides a control, without sprayings. The area under the disease progress curve was lower in plants that received applications of the K and Mn phosphites, whose values ranged between 74 and 81%, compared with the control. The K, Zn, and K+salicyilic acid phosphites were effective in controlling the disease. In addition, disease severity was lower with the application of the K, Zn, and Mn phosphites than with the control. Enzyme (peroxidases and polyphenol oxidases) activity and levels of soluble phenols were higher in common bean plants treated with the K and Mn phosphites, although no change was detected in the levels of soluble lignin in the same tissue. Phosphite application reduces the severity of the disease, can enhance enzymatic activity, and is an effective alternative for the control of anthracnose in common bean.Index terms: Colletotrichum limdemuthianum, Phaseolus vulgaris, alternative control, enzymatic activity, phenolic compounds. Fosfitos para o controle da antracnose em feijoeiro comumResumo -O objetivo deste trabalho foi avaliar o efeito de fosfitos na proteção do feijoeiro comum (Phaseolus vulgaris) contra antracnose. Diferentes formulações de fosfitos foram avaliadas por meio da quantificação da atividade de peroxidases e polifenoloxidases, de fenóis totais e do teor de lignina. Os tratamentos consistiram de pulverizações, nos estádios V4, R5 e R7, com: fosfitos de K, Zn, Mn, K+Mn, K+ácido salicílico e Cu; ácido salicílico; acibenzolar-S-metil; o fungicida azoxistrobina; além de um controle, sem aplicações. A área abaixo da curva de progresso da doença foi menor em plantas que receberam aplicações dos fosfitos de K e Mn, cujos valores variaram entre 74 e 81%, em comparação ao controle. Os fosfitos de K, Zn e K+ácido salicílico foram eficazes no controle da doença. Além disso, severidade da doença foi menor com a aplicação dos fosfitos de K, Zn e Mn quando comparado ao controle. A atividade de enzimas (peroxidases e polifenoloxidases) e os níveis de fenóis solúveis foram mais elevados em plantas de feijão comum tratadas com os fosfitos de K e Mn, embora não tenha sido detectada mudança nos níveis de lignina solúvel no mesmo tecido. A aplicação de fosfitos reduz a severidade da doença, pode potencializar a atividade enzimática e é uma alternativa eficaz para o controle da antracnose no feijoeiro comum.Termos para indexação: Colletotrichum limdemuthianum, Phaseolus vulgaris, controle alternativo, atividade enzimática, compostos fenólicos.

Anthracnose, caused by Colletotrichum lindemuthianum, is one of the main diseases affecting common bean in Brazil, and field losses can reach 100%. Transmission of this pathogen from seeds to seedlings/plants may vary according to environmental conditions and initial inoculum levels, among other factors. The aim of this study was to quantify the transmission rate of C. lindemuthianum, race 65, from infected bean seeds to seedlings/plants under controlled conditions. Seed inoculation was performed by the water conditioning technique in order to obtain seeds with different inoculum potentials as a result of the exposure time of the seeds to the fungus in pure culture, with the potentials denominated P0, P36, P72, P108, and P144. Inoculated and non-inoculated seeds were individually sown and kept in growth chambers under two temperatures, 20 and 26 °C, for a period of 28 days. There was transmission of the pathogen in both asymptomatic and symptomatic plants. The highest total transmission rate (92%) occurred in plants originating from seeds exposed for 144 hours to the fungus at 20 °C.

Colletotrichum lindemuthianum is the causal agent of anthracnose in common bean, and infected seeds are the most typical propagation form of the disease. Thus, using common bean seeds free of C. lindemuthianum is crucial to managing this pest, as well as employing fast and accurate detection techniques to ensure high seed quality. In this study, both conventional and quantitative PCR techniques (cPCR and qPCR) were used for the detection and quantification of C. lindemuthianum in samples of common bean seeds. For that, seeds were inoculated by exposing them to fungal colonies for different periods of time, 0 h, 36 h, 72 h, 108 h and 144 h, each period corresponding to an inoculum potential. Then, they were mixed with healthy seeds, so incidences of 0.25%, 0.50%, 1%, 10%, and 100% of seeds with different inoculum potentials were obtained, in samples of 400 seeds. Both cPRC and qPCR techniques were effective in detecting the fungus. With the cPCR method, the highest sensitivity was recorded in those samples with 10% inoculated seeds with inoculum potential P36. On the other hand, with the qPCR technique, the highest sensitivity in detecting the fungus was observed in samples with 0.25% inoculated seeds with inoculum potential P36.Index terms: Phaseolus vulgaris, anthracnose, PCR.Detecção molecular de Colletotrichum lindemuthianum em amostras de sementes de feijão RESUMO -Colletotrichum lindemuthianum é o agente causal da antracnose do feijoeiro, tendo a semente como uma forma de disseminação. O uso de sementes de feijão livres do patógeno é uma das estratégias de manejo, e o uso de técnicas de detecção precisas e rápidas torna-se indispensável para a análise sanitária prévia de sementes. Neste estudo, as técnicas de PCR convencional (cPCR) e PCR em tempo real (qPCR) foram utilizadas para a detecção e quantificação de C. lindemuthianum em amostras de sementes de feijão. Para isso, sementes foram inoculadas por meio de sua exposição às colônias do fungo por tempos variados, 0, 36, 72, 108, e 144 horas, cada período correspondendo a um potencial de inóculo, P0, P36, P72, P108 e P144. As sementes inoculadas foram misturadas com sementes sadias, obtendo-se incidências de 0,25% 0,50%, 1%, 10% e 100% de sementes para cada potencial de inóculo em amostras de 400 sementes. Tanto a cPRC como a qPCR foram eficazes na detecção do fungo. A partir das amostras de sementes com 10% de incidência e com P36, foi possível detectar o fungo por cPCR. Pela técnica de qPCR o patógeno foi detectado em amostras a partir da incidência de 0,25% no menor potencial de inóculo P36.Termos para indexação: Phaseolus vulgaris, antracnose, PCR.1