Caracterização de Fusarium decemcellulare, F. oxysporum e F. incarnatum em seringueira no estado de São Paulo, resistência clonal e sensibilidade a fungicidas
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Data
2017-05-26
Autores
Pizetta, Marília [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
A heveicultura é de grande importância para o estado de São Paulo, especialmente, no Planalto Paulista. Representa uma das culturas florestais mais plantadas no país, tendo como principal objetivo, a extração do látex, que serve como fonte de matéria-prima para confecção de produtos para as indústrias pneumáticas, hospitalares, calçadistas, etc. Porém, pelo cultivo em caráter perene, o gênero Hevea sofre com o ataque de patógenos, principalmente, fungos. A fusariose, causada por Fusarium spp., é uma doença descrita recentemente, que afeta a casca das plantas adultas, interferindo na explotação de látex pelos produtores. Os sintomas surgem como trincas no caule, seguidos de necrose na casca, podendo causar o “secamento” do látex da árvore e, consequente, morte da planta. Mesmo sabendo-se da importância dessa doença afetando plantações de seringueira, há poucos estudos na literatura sobre os agentes causais, seu comportamento, resistência genética e outras formas de controle da doença. Portanto, no presente estudo objetivou-se caracterizar patogenicamente, morfologicamente e molecularmente 51 isolados de Fusarium spp., realizando, também, teste de resistência clonal e testando diferentes ingredientes ativos no controle “in vitro” dos isolados patogênicos. Para a caracterização morfológica dos esporos, foram avaliados a forma, o tamanho e o número de septos, os tipos de clamidósporos, a formação das fialides e conidiogênese dos microconídios e mesoconídios. A caracterização cultural avaliou a taxa de crescimento micelial, presença ou ausência de esporodóquios e a coloração das colônias. Os estudos moleculares abrangeram análises filogenéticas do DNA dos isolados para as regiões rDNA ITS, rDNA IGS, gene TEF1-α e gene H3. No teste de resistência clonal, foram avaliados diferentes materiais clonais de seringueira quanto à resistência a Fusarium spp., sendo utilizados os clones RRIM 600 (produzido em substrato), RRIM 600 (produzido em solo - controle), IAC 502, IAC 511, IRCA 111, PB 350, PR 255, RRIM 937 (produzidos em solo), todos provenientes de enxertia. Para o teste de controle “in vitro”, foram testados oito produtos comerciais e um ativador de plantas, com os seguintes princípios ativos: clorotalonil, tiofanato metílico, tiofanato metílico + clorotalonil, azoxistrobina + tebuconazol, tebuconazol, piraclostrobina + epoxiconazol, azoxistrobina + ciproconazol, trifloxistrobina + tebuconazol, acibenzolar-S-metílico, dispostos em quatro concentrações (1.000, 100, 10 e 1 μL L-1), sendo três deles registrados para a cultura da seringueira. Baseando-se nos resultados obtidos através dos caracteres morfológicos, culturais e moleculares, foram identificadas três espécies de Fusarium ocorrendo em seringueira no estado de São Paulo, Fusarium decemcellulare, Fusarium incarnatum e Fusarium oxysporum, os quais os dois últimos ainda não foram relatados em seringueira no Brasil. Para o estudo de resistência clonal, os clones IRCA 111 e IAC 502 foram classificados como resistente e suscetível, respectivamente, à espécie F. oxysporum. Os materiais clonais IAC 511 e PR 255 foram resistente e suscetível, respectivamente, à espécie F. incarnatum. Para a espécie F. decemcellulare as informações não foram significativas entre os materiais testados, sendo necessários estudos complementares. As três espécies de Fusarium (F. oxysporum, F. incarnatum e F. decemcellulare) foram sensíveis aos fungicidas a base de tebuconazol e trifloxistrobina + tebuconazol, podendo ser alternativas para o manejo da fusariose em seringueira.
The rubber tree cultivation represents a great importance for the São Paulo state, especially, in the São Paulo uplands. It represents one of the most planted forest crops in the country, with the main objective, the latex extraction, which serves as a source of raw material for the manufacture of products for the pneumatic, hospital, footwear industries, etc. However, by the cultivation on a perennial basis, the genus Hevea suffers from pathogens attack, mainly, fungi. The fusariosis, caused by Fusarium spp., is a disease described recently that affects the bark of adult plants, interfering in the latex exploitation by the producers. The symptoms appear as cracks in the stem, followed by necrosis in the bark, which may cause the “tree drying” of the latex of the tree and, consequently, death of the plant. Even knowing about the importance of this disease affecting rubber tree plantations, there are few studies about the biology of the species, its behavior, genetic resistance and other ways of disease control. Therefore, the study aimed to perform studies about pathogenic, morphological and molecular characterization of 51 isolates of Fusarium spp., also performing a clonal resistance test and to study different active ingredients in the "in vitro" control of the pathogenic isolates. For the morphological characterization of the spores, were evaluated the shape, size and septa number, types of chlamydospores, the formation of phialides and conidiogenesis of the microconidia and mesoconidia. The cultural characterization evaluated the mycelial growth rate, the presence or absence of sporodochia and the pigmentation of the colonies. The molecular studies covered phylogenetic analysis of the isolates DNA analyzes from rDNA ITS region, rDNA IGS region, TEF1-α gene and H3 gene. At the clonal resistance test, different clones of rubber trees were evaluated for resistance to Fusarium spp., the clones were RRIM 600 (produced from substrate), RRIM 600 (produced in soil - control), RRIM 937, PB 350, PR 255, IRCA 111, IAC 511, IAC 502 (produced in soil), all from bud grafting. For the “in vitro” control test, eight commercial products and one plant activator were tested with the following active ingredients: chlorothalonil, methyl thiophanate, methyl thiophanate + chlorothalonil, azoxystrobin + tebuconazole, tebuconazole, pyraclostrobin + epoxiconazole, azoxystrobin + cyproconazole, trifloxystrobin + tebuconazole, acibenzolar-S-methyl, arranged at four concentrations (1,000, 100, 10 and 1 μL L-1), three of them registered for the rubber tree culture. Based on the results obtained through morphological, cultural and molecular characters, three Fusarium species were identified, occurring in rubber trees in the São Paulo state, Fusarium decemcellulare, Fusarium incarnatum and Fusarium oxysporum, which the last two have not yet been reported in rubber trees in Brazil. For the clonal resistance study, the IRCA 111 and IAC 502 clones were classified as resistant and susceptible, respectively, to F. oxysporum species. The clonal materials IAC 511 and PR 255 were resistant and susceptible, respectively, to F. incarnatum species. For the F. decemcellulare species, the information was not significant among the tested materials and additional studies were necessary. The three Fusarium species (F. oxysporum, F. incarnatum and F. decemcellulare) were sensitive to fungicides based on tebuconazole and trifloxystrobin + tebuconazole, and could be an alternative to the management of the fusariosis in rubber tree.
The rubber tree cultivation represents a great importance for the São Paulo state, especially, in the São Paulo uplands. It represents one of the most planted forest crops in the country, with the main objective, the latex extraction, which serves as a source of raw material for the manufacture of products for the pneumatic, hospital, footwear industries, etc. However, by the cultivation on a perennial basis, the genus Hevea suffers from pathogens attack, mainly, fungi. The fusariosis, caused by Fusarium spp., is a disease described recently that affects the bark of adult plants, interfering in the latex exploitation by the producers. The symptoms appear as cracks in the stem, followed by necrosis in the bark, which may cause the “tree drying” of the latex of the tree and, consequently, death of the plant. Even knowing about the importance of this disease affecting rubber tree plantations, there are few studies about the biology of the species, its behavior, genetic resistance and other ways of disease control. Therefore, the study aimed to perform studies about pathogenic, morphological and molecular characterization of 51 isolates of Fusarium spp., also performing a clonal resistance test and to study different active ingredients in the "in vitro" control of the pathogenic isolates. For the morphological characterization of the spores, were evaluated the shape, size and septa number, types of chlamydospores, the formation of phialides and conidiogenesis of the microconidia and mesoconidia. The cultural characterization evaluated the mycelial growth rate, the presence or absence of sporodochia and the pigmentation of the colonies. The molecular studies covered phylogenetic analysis of the isolates DNA analyzes from rDNA ITS region, rDNA IGS region, TEF1-α gene and H3 gene. At the clonal resistance test, different clones of rubber trees were evaluated for resistance to Fusarium spp., the clones were RRIM 600 (produced from substrate), RRIM 600 (produced in soil - control), RRIM 937, PB 350, PR 255, IRCA 111, IAC 511, IAC 502 (produced in soil), all from bud grafting. For the “in vitro” control test, eight commercial products and one plant activator were tested with the following active ingredients: chlorothalonil, methyl thiophanate, methyl thiophanate + chlorothalonil, azoxystrobin + tebuconazole, tebuconazole, pyraclostrobin + epoxiconazole, azoxystrobin + cyproconazole, trifloxystrobin + tebuconazole, acibenzolar-S-methyl, arranged at four concentrations (1,000, 100, 10 and 1 μL L-1), three of them registered for the rubber tree culture. Based on the results obtained through morphological, cultural and molecular characters, three Fusarium species were identified, occurring in rubber trees in the São Paulo state, Fusarium decemcellulare, Fusarium incarnatum and Fusarium oxysporum, which the last two have not yet been reported in rubber trees in Brazil. For the clonal resistance study, the IRCA 111 and IAC 502 clones were classified as resistant and susceptible, respectively, to F. oxysporum species. The clonal materials IAC 511 and PR 255 were resistant and susceptible, respectively, to F. incarnatum species. For the F. decemcellulare species, the information was not significant among the tested materials and additional studies were necessary. The three Fusarium species (F. oxysporum, F. incarnatum and F. decemcellulare) were sensitive to fungicides based on tebuconazole and trifloxystrobin + tebuconazole, and could be an alternative to the management of the fusariosis in rubber tree.
Descrição
Palavras-chave
Heveicultura, Fusariose, Taxonomia fúngica, Enxertia, Controle químico, Identificação de fungos, Hevea brasiliensis, Genótipos, Fusarium oxysporum, Fusarium incarnatum, Fusarium decemcellulare, Resistência clonal, Ingredientes ativos, Rubber tree cultivation, Fusariosis, Fungi taxonomy, Grafting, Chemical control, Fungi identification, Genotypes, Clonal resistance, Active ingredients