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SOBREVIVÊNCIA DE Stenocarpella Maydis E Stenocarpella Macrospora EM RESTOS CULTURAIS DE MILHO

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SOBREVIVÊNCIA DE Stenocarpella Maydis E Stenocarpella Macrospora EM RESTOS CULTURAIS DE MILHO RICARDO TREZZI CASA SOBREVIVÊNCIA DE Stenocarpella maydis E Stenocarpella macrospora EM RESTOS CULTURAIS DE MILHO Tese apresentada à Universidade Federal de Viçosa, como parte das exigências do Programa de Pós-graduação em Fitopatologia, para obtenção do Título de “Doctor Scientiae”. VIÇOSA MINAS GERAIS - BRASIL 2000 RICARDO TREZZI CASA SOBREVIVÊNCIA DE Stenocarpella maydis E Stenocarpella macrospora EM RESTOS CULTURAIS DE MILHO Tese apresentada à Universidade Federal de Viçosa, como parte das exigências do Programa de Pós-graduação em Fitopatologia, para obtenção do Título de “Doctor Scientiae”. APROVADA: 13 de dezembro de 2000. Prof. Dr. Laércio Zambolim Prof. Dr. Erlei Melo Reis (Orientador) (Co-orientador) Prof. Dr. Kiyoshi Matsuoka Dr. Geraldo Martins Chaves Prof. Dr. Francisco Xavier Ribeiro do Vale Esta dissertação é dedicada a minha mãe Ignêz AGRADECIMENTO Ao professor Erlei, pela orientação, amizade e por grande parte de todo conhecimento profissional obtido até aqui. Ao professor Laércio, pela orientação, amizade e confiança em meu trabalho. Ao Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), pelo apoio financeiro no período de estudo. À Universidade de Passo Fundo, pela colaboração e oportunidade de trabalho. Aos funcionários da UFV e UPF, em especial aos amigos Cinara, Naiara e Paulo, pelo apoio a mim dedicado. Ao corpo docente, funcionários e colegas do curso de pós-graduação, pela amizade, vivência e ensinamentos transmitidos. Aos participantes da banca examinadora, pela atenção dedicada. À Melissa, pelo seu carinho, amor e incentivo. Ao Rubens, Ulisses e Luciana, pela amizade, apoio e incentivo. À minha irmã Marta, colega e amiga, pelo auxílio e dedicação prestado. Aos amigos e familiares, pelo incentivo prestado. A todos que, de forma direta ou indireta, me apoiaram. BIOGRAFIA RICARDO TREZZI CASA, nasceu em 3 de fevereiro de 1969, natural de Passo Fundo, RS, Brasil. Engenheiro Agrônomo, CREA 81318-D, formado em dezembro de 1992 pela Faculdade de Agronomia da Universidade de Passo Fundo, RS. Foi bolsista de iniciação científica pelo Conselho Nacional de Desenvolvimento Científico e Tecnológico - CNPq, durante os anos de 1990/93, no Centro Nacional de Pesquisa de Trigo, CNPT/EMBRAPA, sob a orientação do pesquisador Erlei Melo Reis. Em março de 1995, ingressou no curso de mestrado do Departamento de Fitopatologia da Universidade Federal de Viçosa, onde obteve o título de “Magister Scientiae” em fevereiro de 1997. Atualmente, vem desenvolvendo trabalhos de pesquisa no controle de doenças do milho e de cereais de inverno, com ênfase em patologia de sementes e no estudo de práticas culturais, como, por exemplo, o plantio direto. Sua linha de pesquisa visa reduzir o inóculo dos patógenos em suas fontes. ÍNDICE Página RESUMO ..................................................................................................... vii ABSTRACT ................................................................................................. ix 1. INTRODUÇÃO ........................................................................................ 1 2. REVISÃO DE LITERATURA ................................................................. 5 2.1 Nomes comuns ................................................................................... 5 2.2 Etiologia e taxonomia ........................................................................ 6 2.3 Histórico e ocorrência ........................................................................ 9 2.4 Importância econômica ...................................................................... 11 2.5 Hospedeiros ....................................................................................... 13 2.6 Sintomatologia ................................................................................... 13 2.7 Ciclo biológico de Stenocarpella macrospora e S. maydis ................. 15 2.7.1 Fontes de inóculo ..................................................................... 15 2.7.2 Disseminação ........................................................................... 16 2.7.3 Inoculação e colonização ......................................................... 17 2.7.4 Sobrevivência .......................................................................... 19 2.8 Medidas de controle ........................................................................... 20 2.8.1 Resistência varietal .................................................................. 21 2.8.2 Rotação de culturas .................................................................. 23 2.8.3 Controle do patógeno associado à semente ............................... 25 2.8.4 Balanço adequado da fertilidade do solo .................................. 26 2.8.5 População de plantas ................................................................ 27 Página 3. CAPÍTULO I - Decomposição dos restos culturais do milho e sobrevivência saprofítica de Stenocarpella macrospora e Stenocarpella maydis ............................ 28 Resumo ..................................................................................................... 28 Introdução ................................................................................................. 30 Material e métodos ................................................................................... 31 Resultados e discussão .............................................................................. 36 Conclusões ............................................................................................... 51 Referências bibliográficas ......................................................................... 52 4. CAPÍTULO II – Dispersão vertical e horizontal de conídios de Stenocarpella macrospora e Stenocarpella maydis ....... 56 Resumo ..................................................................................................... 56 Introdução ................................................................................................. 57 Material e métodos ................................................................................... 58 Resultados e discussão .............................................................................. 61 Conclusões ............................................................................................... 77 Referências bibliográficas ......................................................................... 78 5. CAPÍTULO III - Efeito da temperatura e do regime luminoso no crescimento do micélio, germinação dos conídios e extrusão do cirro de Stenocarpella macrospora e Stenocarpella maydis................................................... 83 Resumo ..................................................................................................... 83 Introdução ................................................................................................. 85 Material e métodos ................................................................................... 86 Resultados e discussão .............................................................................. 89 Conclusões ............................................................................................... 98 Referências bibliográficas ......................................................................... 99 6. REFERÊNCIAS BIBLIOGRÁFICAS ....................................................... 102 7. APÊNDICES ............................................................................................ 119 RESUMO CASA, Ricardo Trezzi, D.S., Universidade Federal de Viçosa, dezembro 2000. Sobrevivência de Stenocarpella maydis e Stenocarpella macrospora em restos culturais do milho. Orientador: Laércio Zambolim. Co-orientador: Erlei Melo Reis. Conselheiro: Francisco Xavier Ribeiro do Vale. Em ensaios conduzidos no campo e laboratório, estudaram-se as associações dos fungos Stenocarpella maydis e S. macrospora com os restos culturais do milho. No campo, demonstrou-se que a presença dos resíduos culturais de milho sobre a superfície do solo de uma estação de cultivo para outra, garante a presença e a viabilidade dos fungos S. maydis e S. macrospora. A decomposição da palha do milho mantida na superfície do solo foi de 78,5 % aos 29 meses de exposição no campo; além disto, a decomposição dos restos culturais incorporados ao solo é mais rápida do que mantidos sobre o solo. O número de conídios de S. maydis e S. macrospora capturados no ar foi inversamente proporcional à distância vertical e horizontal da fonte de inoculo, constituída de palha infectada. Os conídios foram capturados até altura de 2,0 m acima e distantes 120 m da fonte de inóculo. A maior quantidade de conídios capturados no ar ocorreu durante o dia, sendo os esporos coletados isoladamente ou agrupados em cirros, não necessitando estarem veiculados a gotículas d’água. Em laboratório, determinou-se que a faixa de temperatura de 23 a 28 oC proporcionou o maior crescimento do micélio de S. maydis e S. macrospora, tanto sob luz contínua como sob fotoperíodo de 12 h. O micélio dos fungos não cresceu à temperatura inferior a 10 oC e superior a 40 oC. A faixa de temperatura de 26 a 33 oC propiciou a maior porcentagem de germinação dos conídios, sendo que ambas espécies germinaram mais rapidamente na presença de luz constante. Após 24 h de incubação os conídios de S. macrospora e S. maydis não germinaram nas temperaturas de 5 e 45 oC. A extrusão do cirro de conídios em colmos de milho foi maior na faixa térmica de 30 a 35 oC sob luz contínua. Este trabalho apresenta as bases
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