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Master's Dissertation
Full name
Leila Nakati Coutinho
Knowledge Area
Date of Defense
Piracicaba, 1994
Title in Portuguese
Taxonomia, variabilidade, patogenicidade e controle de <i>Verticillium</i> em <i>Agaricus bisporus</i> (Lange) Singer
Keywords in Portuguese
Abstract in Portuguese
O presente trabalho foi efetuado visando isolar <i>Verticillium</i> spp a partir de cultivos comerciais de cogumelos caracterizá-los taxonomicamente, morfológica e fisiologicamente, comparar os métodos de preservação dos isolados obtidos, e verificação de sua patogenicidade. Foi estudado também o efeito ?in vitro? de fungicidas sobre <i>Agaricus bisporus, Agaricus bitorquis</i> e vários isolados de <i>Verticillium</i>. Verificou-se que a principal doença do cogumelo comestível (<i>Agaricus bisporus</i>) na região de Mogi das Cruzes, SP é causada por <i>Verticillium</i> cujo agente causal foi identificado como <i>V. fungicola</i>. Foram isoladas 12 linhagens do fungo. Os melhores métodos para preservação da viabilidade e estabilidade fisiológica dos isolados de <i>Verticillium</i> para a finalidade de pesquisa foram determinados como sendo os métodos da água destilada ou de Castellani, e da liofilização dos conídios. A temperatura ótima para o crescimento micelial e produção de conídios, dos 12 isolados de <i>V. fungicola</i> esteve entre 21-27°C, em meios de Batata Dextrose Ágar (BDA) e Meio de A veia Ágar (MAA). A melhor esporulação ocorreu em meio de BDA. O ponto térmico letal dos conídios esteve entre 39-40°C. Quando uma suspensão de conídios foi inoculada por aspersão na solo de cobertura todos os isolados foram patogênicos para o cogumelo comestível (<i>A. bisporus</i>), causando manchas rachaduras, depreciando o valor comercial do produto e resultando em sintomas típicos de ?bolha seca? que consiste na produção de corpos de frutificação disformes. Estudos ?in vitro? sobre a ação de fungicidas no crescimento micelial de <i>V. fungicola</i> e seu efeito sobre <i>A. bisporus</i> e <i>A. bitorquis</i> demonstraram que o procloraz+Mn foi o mais eficiente controlador do fungo, enquanto que o benomil, que já tem sido recomendado no Brasil para o controle da ?bolha seca?, embora tenha demonstrado uma eficiência semelhante ao procloraz+Mn, não foi eficiente para todos os isolados, pois dois deles foram resistentes ou tolerantes. Este é o primeiro relato de resistência à benomil em <i>Verticillium</i> atacando cogumelos comestíveis no Brasil.
Title in English
Taxonomy, variability, pathogenicity and control of </i>Verticillium</i> on <i>Agaricus bisporus</i> (Lange) Singer
Abstract in English
In the present dissertation Verticillium samples were obtained from diseased mushrooms collected in several producing properties in the region of Moji das Cruzes, SP with the purpose of developing taxonomic, morphological, physiological, and pathological studies in order to caracterize the envolved species Studies were also carried out to establish the best preservation method of the <I>Verticillium</I> isolates during the studies. ?In vitro? tests on the effect of differents fungicides on the growth of <i>Agaricus bisporus, A. bitorquis</i> and on the <i>Verticillium</i> control were made. Twelve <i>Verticillium</i> isolates were obtained. A species, of <i>Gliocladium</i>, probably a nematode trapping fungus, was also isolated. The best preservation method for maintenance viability and physiological stability of the <i>Verticillium</i> samples were the Castellani?s and the lyophilization methods. The best mycelial growth temperature for all the <i>Verticillium fungicola</i> isolates was determined to be around 21-27°C, but most of them had the best growth at 24°C. The best temperature for conidia production in Potato Dextose Agar (PDA) and Oat Extract Agar was found to be between 21-27°C. The best sporulation associated with the best temperature occured in PDA. The conidia thermal death point is 39-40°C. <i>Verticillium</i> pathogenicity assays to <i>A. bisporus</i> showed that all the 12 isolates were pathogenic to <i>A. bisporus</i> causing cinnamon brown and irregular discolored spots on the surface of the cap. Many spots of a varying size and outline may occur. Under moist condition, the enlarging spots may coalesce to form a large blotch. Later the spot may become depressed and sunken. These mushrooms are edible, but are of reduced quality and commercial value. The parasite can also invade the tissue of the stem thus causing a splitting and splintering, often producing a tilted and drawled cap. When such mushrooms are cut open, a hollow cavity is frequently seen, the walls of which are covered with a whitish growth. The mushroom becomes dry, shrunken, distorted and unfit for sale. Finally, the ?bubble? formation is indicative of heavy contamination of the casing soil and it was more present in the end of the cultures. ln this case the newly forming buttons are infected at a very early stage. The invading hyphae of the parasite arrest development leading to pileo malformations. The stem becomes swollen into a puffball-like structure which do not decay but remain dry and leathery. ln this disease stage the mushroom production is completely spoiled and damaged. ?ln vitro? studies fungicides action of fungicides of the mycelial growth on <i>V. fungicola, A. bisporus</i> and <i>A. bitorquis</i> showed that prochloraz+Mn was the most efficient. ln Brazil benomyl have been recommended for dry bubble control. Although benomyl is as efficient as prochloraz+Mn for dry bubble control. Two benomyl resistant or tolerant isolates were detected in Moji das Cruzes and surrounding areas.
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