Mancha de mirotécio em algodoeiro causada por Myrothecium roridum
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Data
2006-09-01
Autores
Meyer, Maurício Conrado
Silva, Juliano César da
Maia, Gerliane Lorena
Bueno, César Júnior [UNESP]
Souza, Nilton Luiz de [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Grupo Paulista de Fitopatologia
Resumo
A mancha de mirotécio causada por Myrothecium roridum Tode ex Fr. foi observada em lavouras de algodão no sul do Maranhão, causando reduções de produtividade de até 60%. Os sintomas da doença são lesões necróticas, circulares, com estruturas salientes, os esporodóquios, de distribuição irregular. Foram observadas lesões nos pecíolos, brácteas, folhas e maçãs de algodoeiro cv. Deltapine Acala 90, Fibermax 966 e Sure Grow 821. O isolamento do fungo foi realizado em meio de cultura batata-dextrose-ágar (BDA). O teste de patogenicidade foi realizado em maçãs sadias, destacadas de algodoeiro cv. Fibermax 966, no estádio vegetativo R6, previamente desinfestadas. Foram testados 13 isolados de M. roridum, oito provenientes de algodão e cinco de soja. Avaliações das estruturas fúngicas foram realizadas com auxílio de microscópio óptico equipado com um micrômetro ocular. Os isolados causaram infecções em maçãs de algodão e destacou-se como mais agressivo o MA-75, proveniente de algodão, apresentando diâmetro médio de lesão de 1,3cm, aos sete DAI e 2,7cm aos 14 DAI. Todos os isolados formaram esporodóquios dispostos concenticamente em meio BDA. Os conídios são unicelulares, hialinos a oliváceos, abundantemente produzidos em massa verde-oliva a preta. Os conídios de isolados provenientes de algodão mediram, em média, 5,1µm x 1,5µm, e os obtidos de soja, 5,8µm x 1,5µm. Estes resultados relatam a ocorrência da mancha de mirotécio, causada por M. roridum, em lavouras comerciais de algodão no Brasil.
Myrothecium leaf spot caused by Myrothecium roridum Tode ex Fr. was observed on cotton fields in Maranhão State, Brazil, causing yield reduction of up to 60%. Disease symptoms are lesions with concentric necrotic rings, with salient structures (sporodochia) irregularly distributed. Symptoms were observed on petioles, bracts, leaves and bolls of cotton cultivars Deltapine Acala 90, Fibermax 966 and Sure Grow 821. The pathogen was isolated and cultivated on potato-dextrose-agar (PDA) medium. The pathogenicity was evaluated on detached healthy bolls from cotton cv. Fibermax 966 (R6 vegetative stage), previously disinfested. Thirteen isolates of M. roridum were tested, which included 8 from cotton and 5 from soybean. Fungal structures were evaluated by using light microscope with ocular micrometer. The isolates infected cotton bolls and the MA-75 was the most aggressive strain. In average lesion diameter is 1,3cm long at 7 days after inoculation, and 2,7cm at 14 days. They also formed sporodochia concentrically disposed on PDA. Conidia are hyalines to dilute olivaceous, single-celled, abundantly produced in a dark green to black mass. Spores from cotton isolates are 5,1µm x 1,5µm in size, and from soybean isolates are 5,8µm x 1,5µm. This is the first report of Myrothecium leaf spot in Brazilian cotton fields.
Myrothecium leaf spot caused by Myrothecium roridum Tode ex Fr. was observed on cotton fields in Maranhão State, Brazil, causing yield reduction of up to 60%. Disease symptoms are lesions with concentric necrotic rings, with salient structures (sporodochia) irregularly distributed. Symptoms were observed on petioles, bracts, leaves and bolls of cotton cultivars Deltapine Acala 90, Fibermax 966 and Sure Grow 821. The pathogen was isolated and cultivated on potato-dextrose-agar (PDA) medium. The pathogenicity was evaluated on detached healthy bolls from cotton cv. Fibermax 966 (R6 vegetative stage), previously disinfested. Thirteen isolates of M. roridum were tested, which included 8 from cotton and 5 from soybean. Fungal structures were evaluated by using light microscope with ocular micrometer. The isolates infected cotton bolls and the MA-75 was the most aggressive strain. In average lesion diameter is 1,3cm long at 7 days after inoculation, and 2,7cm at 14 days. They also formed sporodochia concentrically disposed on PDA. Conidia are hyalines to dilute olivaceous, single-celled, abundantly produced in a dark green to black mass. Spores from cotton isolates are 5,1µm x 1,5µm in size, and from soybean isolates are 5,8µm x 1,5µm. This is the first report of Myrothecium leaf spot in Brazilian cotton fields.
Descrição
Palavras-chave
fungo, Gossypium hirsutum, nova doença, descrição, fungus, Gossypium hirsutum, first report, disease description
Como citar
Summa Phytopathologica. Grupo Paulista de Fitopatologia, v. 32, n. 4, p. 390-393, 2006.