The activities of the enzymes chalcone synthase (CHS) and phenylalanine ammonia-lyase (PAL) were measured in leaf extracts obtained from four cultivars of the common bean (AB 136, Rio Tibagi, Carioca and Macanudo). Two stages of plant development were examined: plantlets (V2) and the onset of blooming (R6). Initially, the plants were either treated with salicylic acid or inoculated with the delta race of Colletotrichum lindemuthianum (inductive fungus) and after three days they were evaluated for enzyme activity. Afterwards, all plants were inoculated (challenged) with the virulent pathotype 33/95 of C. lindemuthianum except for the water control. Five days later, the activities of PAL and CHS were evaluated. There were significant changes in the activities of both enzymes three days after treatment with salicylic acid or inductive fungus when compared to the control. Five days after inoculation with with the virulent pathotype 33/95 of C. lindemuthianum CHS activity in the Macanudo was similar to control plants that were not treated with salicylic acid or the inductive fungus but inoculated with 33/95 C. lindemuthianum. The increase in enzyme activity after challenge with 33/95 C. lindemuthianum was greatest for the salicylic acid treatment in the cultivar AB 136, followed by Rio Tibagi and Carioca.

Resumo -O objetivo deste trabalho foi avaliar a influência das enzimas peroxidase e polifenoloxidase na resistência à antracnose de quatro cultivares de feijão. Plântulas de feijão foram pulverizadas com ácido salicílico e com a raça delta de Colletotrichum lindemuthianum (fungo indutor) e submetidas à inoculação do patótipo virulento 33/95 de C. lindemuthianum três dias após a aplicação do fungo indutor e do ácido salicílico. Essas plantas foram avaliadas quanto à atividade enzimática e teores de fenóis, três dias após a aplicação do fungo indutor e cinco dias após a inoculação do patótipo virulento. Acréscimos nas atividades dessas enzimas foram maiores nos tratamentos com ácido salicílico e fungo indutor em todas as cultivares. Maiores estímulos nas atividades enzimáticas foram observados nas cultivares com maior resistência à doença. Constatou-se o aparecimento de uma isoperoxidase nos tratamentos com fungo indutor, ácido salicílico, após inoculação do patótipo virulento, e na testemunha, nas cultivares AB 136, Rio Tibagi e Macanudo. Houve correlação positiva entre as atividades da peroxidase e da polifenoloxidase, os teores de compostos fenólicos e a resistência à antracnose.Termos para indexação: Phaseolus vulgaris, Colletotrichum lindemuthianum, resistência sistêmica adquirida. Peroxidase and polyphenol oxidase activity in bean anthracnose resistanceAbstract -The objective of this work was to evaluate the influence of peroxidase and polyphenol oxidase enzymes in anthracnose resistance of four bean cultivars. Seedlings were sprinkled with salicylic acid and delta race of Colletotrichum lindemuthianum (inducer fungus) and after three days they were inoculated with 33/95 virulent pathotype of C. lindemuthianum. Enzyme activity and phenol levels were evaluated three days after inducer fungus application and five days after inoculation with virulent pathotype. Plants treated with salicylic acid and inducer fungus presented higher activity increases of both enzymes, in all cultivars. Higher impulses in enzymatic activity were observed in cultivars with higher disease resistance. One isoperoxidase appeared in treatments with inducer fungus, salicylic acid, after inoculation with virulent pathotype, and in control plants, in AB 136, Rio Tibagi and Macanudo cultivars. Positive correlation was observed among peroxidase and polyphenol oxidase activity, phenolic compound levels and anthracnose resistance.

Resumo -O objetivo deste trabalho foi avaliar o potencial da raça delta avirulenta do fungo Colletotrichum lindemuthianum, como protetora contra raças virulentas deste fungo e quanto à capacidade de induzir resistência sistêmica em feijoeiro-comum (Phaseolus vulgaris). Quatro cultivares de feijoeiro foram avaliadas quanto às alterações nas atividades de beta-1,3-glucanase e quitinase, em dois estádios de desenvolvimento (V2 e R6), três dias após a aplicação de suspensão de esporos de C. lindemuthianum raça delta avirulenta, em comparação com aplicações de água e ácido salicílico. As plantas foram, então, infectadas com o patótipo virulento 33/95 de C. lindemuthianum em suspensão e, depois de cinco dias, foram reavaliadas quanto à atividade das enzimas. Observaram-se acréscimos signifi cativos nas atividades da beta-1,3-glucanase e quitinase, após inoculação do fungo indutivo, nas duas avaliações, nos dois estádios de desenvolvimento. As atividades da beta-1,3-glucanase e da quitinase variaram entre as cultivares e entre os estádios de desenvolvimento das plantas. A correlação entre o índice de severidade da doença e a atividade das enzimas foi altamente signifi cativa. O uso de C. lindemuthianum raça delta avirulenta diminuiu a severidade da doença e pode ter potencial para controlar a antracnose do feijoeiro.Termos para indexação: Phaseolus vulgaris, ácido salicílico, beta-1,3-glucanase, controle biológico, enzimas hidrolíticas, quitinase. Induction of systemic resistance to anthracnose in common bean by the avirulent delta race of Colletotrichum lindemuthianumAbstract -The objectives of this work were to evaluate the potential of the avirulent delta race of Colletotrichum lindemuthianum as a protector against virulent races of this fungus and induce systemic resistance to anthracnose in common bean (Phaseolus vulgaris). Four common bean cultivars were evaluated for changes in the activities of beta-1,3-glucanase and chitinase at two common bean developmental stages, V2 and R6, three days after the infection with delta race of C. lindemuthianum, in comparison with control applications of water and salicylic acid. The plants were then infected with a spore suspension of 33/95, a virulent C. lindemuthianum patotype and reevaluated fi ve days later for the enzyme activities. Signifi cant increases in the activities of both beta-1,3-glucanase and chitinase were observed after inoculation of inductive fungus at the two evaluation periods, at both plant development stages. The activities of both beta-1,3-glucanase and chitinase varied among cultivars and among plant development stages. A signifi cant correlation was observed between the disease severity and the enzyme activity. The avirulent delta race of C. lindemuthianum reduced the severity of anthracnose on common bean and may have the potential to control the disease.

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