RESUMOEste trabalho teve como objetivos avaliar, in vitro, a fungitoxicidade dos extratos brutos aquosos (EBAs) de Achillea millefolium, Artemisia camphorata, Cymbopogon citratus e Rosmarinus officinalis contra Alternaria solani e o efeito protetor destes extratos em plantas de tomateiro em casa-de-vegetação. Para verificar a atividade antifúngica, os EBAs foram incorporados ao BDA e avaliadas a inibição do crescimento micelial, a esporulação e a germinação de conídios. O efeito protetor em plantas foi avaliado através da pulverização preventiva (72h antes da inoculação) dos EBAs, nas concentrações de 10 e 20%, nas duas primeiras folhas. A severidade da doença foi verificada 15 dias após a inoculação. Verificou-se que os EBAs não inibiram o crescimento micelial, mas tiveram efeitos significativos na redução da esporulação e da germinação de conídios, principalmente os EBAs de A. camphorata, C. citratus e R. officinalis, a partir da concentração de 20%. Já em relação à proteção das plantas verificou-se uma redução no número de lesões em relação à testemunha, nas folhas acima das tratadas, observando o efeito sistêmico dos extratos. Os extratos estudados podem ser promissores no controle da pinta-preta em tomateiro. Palavras-chave: Alternaria solani, controle alternativo. ABSTRACT Antifungal activity and protection of tomato plants by extracts of medicinal plantsThe present work aimed to evaluate, in vitro, the fungitoxicity of aqueous crude extracts (ACEs) of Achillea millefolium, Artemisia camphorata, Cymbopogon citratus and Rosmarinus officinalis to Alternaria solani and their protective effect on tomato plants under greenhouse conditions. To evaluate the antifungal activity of ACEs, they were incorporated into potato-dextrose-agar medium and the inhibition of mycelial growth, sporulation and conidia germination was evaluated. The protective effect in plants was evaluated by means of preventive spraying (72 hours before inoculation) with ACE, at concentrations of 10 and 20%, in the first two leaves. Disease severity was verified 15 days after inoculation. It was observed that ACEs did not inhibit mycelial growth, but they had significant effects on the reduction of germination and sporulation, especially the ACEs of A. camphorata, C. citratus and R. officinalis, at concentrations up to 20%. A reduction was observed in the number of lesions in relation to the control, in leaves above those treated, observing the systemic effect of the extracts. The extracts from the studied plants may be promising in the control of early blight on tomato plants.
A área total irrigada em pomares cítricos no Brasil tem aumentado ao longo das décadas. A principal causa desse aumento deve-se ao uso de porta-enxertos tolerantes à Morte Súbita dos Citros, porém menos tolerantes à seca que o limão Cravo. Este trabalho tem como objetivo estudar a influência do porta-enxerto e do tipo de solo na transpiração de plantas jovens de laranjeira Valência. O experimento foi conduzido em estufa, nas dependências do Departamento de Engenharia de Biossistemas da ESALQ/USP. Mudas de laranjeira foram plantadas em caixas de 500 L. Determinou-se, simultaneamente, a transpiração de 20 plantas por meio de sondas de dissipação térmica (fluxo de seiva). Foram medidas a radiação solar global, a umidade relativa e a temperatura do ar com sensores instalados a 2 m de altura no centro da estufa. A evapotranspiração de referência (EToPM) foi calculada pelo método de Penman-Monteith proposto pela FAO. De acordo com os resultados encontrados, conclui-se que a transpiração das plantas de laranjeira Valência é influenciada não só pelo tipo de porta-enxerto utilizado, como também pelo crescimento em área foliar e estádio fenológico, sendo que sua relação com a EToPM não é linear em toda a faixa de demanda evaporativa da atmosfera.
The bacterial spot of tomato, caused by Xanthomonas spp., is a very important disease, especially in the hot and humid periods of the year. The chemical control of the disease has not been very effective for a number of reasons. This study aimed to evaluate, under greenhouse conditions, the efficacy of leaf-spraying chemicals (acibenzolar-S-methyl (ASM) (0.025 g.L−1), fluazinam (0.25 g.L−1), pyraclostrobin (0.08 g.L−1), pyraclostrobin + methiran (0.02 g.L−1 + 2.2 g.L−1), copper oxychloride (1.50 g.L−1), mancozeb + copper oxychloride (0.88 g.L−1 + 0.60 g.L−1), and oxytetracycline (0.40 g.L−1)) on control of bacterial spot. Tomatoes Santa Clara and Gisele cultivars were pulverized 3 days before inoculation with Xanthomonas perforans. The production of enzymes associated with resistance induction (peroxidase, polyphenol oxidase, phenylalanine ammonia-lyase, β-1,3-glucanase, and protease) was quantified from leaf samples collected 24 hours before and 24 hours after chemical spraying and at 1, 2, 4, 6, and 8 days after bacterial inoculation. All products tested controlled bacterial spot, but only ASM, pyraclostrobin, and pyraclostrobin + metiram increased the production of peroxidase in the leaves of the two tomato cultivars, and increased the production of polyphenol oxidase and β-1,3-glucanase in the Santa Clara cultivar.
The control of tomato bacterial spot by the application of chemicals was evaluated on field condition during two trials. Thirty days after transplanting and every 14 days the tomato plants PA-529 hybrid were sprayed with acibenzolar-S-methyl (2.5 g·100) and water (control), totaling five applications during the crop cycle. Forty days after transplanting, the plants were inoculated with a Xanthomonas perforans isolate (10 7 UFC·mL -1 ), disease severity was assessed (10, 19, 29, and 36 days after inoculation), and the area under the disease progress curve was calculated. All chemicals controlled the disease, but better results for total mass and number of fruit was obtained for fluazinam, pyraclostrobin, pyraclostrobin + metiram, copper oxychloride, and mancozeb + copper oxychloride in the first trial, and pyraclostrobin and pyraclostrobin + metiram in the second trial. The average fruit weight, °Brix, pH and total acidity were not affected by the application of the chemicals. The enzymatic activity of the polyphenol oxidase and peroxidase was higher in the first trial, but in the second, only the polyphenoloxidase had the highest activity in the treatments with acibenzolar-S-methyl, pyraclostrobin, and pyraclostrobin + metiram on tomato leaves. Products containing pyraclostrobin increased the activity of some enzymes without reducing the productivity.
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