Subsídios para o manejo cultural e fitopatológico de Cyrtopodium cardiochilum (Orchidaceae)

• Autor(a) principal: Lima, Brenda Ventura de
• Data de Publicação: 2012
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/4411
• topic: Substrato; Fertilizante; Orquídea; Micobiota fitopatogênica; Substrate; Fertilizer; Orchid; Pathogenic mycobiota; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOSSANIDADE::FITOPATOLOGIA

Cyrtopodium cardiochilum is a native Brazilian orchid that has known potential for the production of extracts of interest for the manufacture of cosmetics and pharmaceuticals. The commercial interest in this orchid species and the absence of published information on crop management and disease managements for this species led to the present study. This work served the purpose of generating the background information necessary for the domestication and management of this orchid. Selected substrates and their combinations were tested, for the cultivation of C. cardiochilum, namely: gneiss gravel, expanded clay pellets, shingles, coconut shells and. All substrates were equivalent for the orchid cultivation, although the mixture of expanded clay pellets and gneiss gravel at 1:1 (v/v) resulted in the highest values of biomass. A multi-nutrient formulation having a composition compatible with the nutrient requirements of C. cardiochilum was prepared and the effect of different doses of this fertilizer on the growth of C. cardiochilum was evaluated. The analysis of the dose-response curves allowed it to be inferred that the dose resulting in maximum biomass production was 100 mg/pot/week. Different compositions of culture media for in vitro seminiferous cultivation of C. cardiochilum various proportions of activated charcoal, sucrose and salts of the Supply medium (S) - were tested in order to determine the best composition for the production of C. cardiochilum plantlets. A composition of 3.0 g L-1 of activated charcoal, 33 g L-1 of sucrose and 3.2 g L-1 of salts of the S medium yielded the highest dry biomass of C. cardiochilum plantlets. A preliminary survey of the pathogenic mycobiota associated to C. cardiochilum was also conducted. Six fungal species were collected: Sphenospora kevorkianii, Colletotrichum fructicola, Fusarium solani, Bionectria ochroleuca, Botrytis cinera and Alternaria sp. The first four fungal species were regarded as the most important and had their morphology examined in detail. Molecular methods were used to further clarify the identity of C. fructicola, F. solani and B. ochroleuca. Finally, fungicides were evaluated for the control of plant rots caused by F. solani and B. ochroleuca in vitro and in vivo. The in vitro essay involved four active ingredients (thiram, thiofanate methyl, captan and metalaxyl- M + mancozeb). Both F. solani and B. ochroleuca had their mycelial growth in culture effectively inhibitted by thiram and thiofanate methyl at concentrations of 0.05 g 100 mL-1 and 0.025 g 100 mL-1, respectively. Prior to the in vivo test aimed at evaluating the chemical control of the plant rots a screening of selected orchid species was performed in search for a surrogate species to be used as a substitute for C. cardiochilum due to the difficulty of obtaining a sufficiently big and homogenous stand of plants for use in the experiments. Such species should be readily available in the potted orchid market and also susceptible to both B. ochroleuca and F. solani. A test was also performed aimed at determining the appropriate inoculum concentration to be used in the in vivo chemical control experiment. Among the nine orchid genera which were tested Cattleya and Laelia proved to be adequate surrogates. All inoculum concentrations which were tested for F. solani and B. ochroleuca (103, 104, 105 e 106 spores⁄mL) were capable of causing necrosis in the stand of surrogate plants - Cattleya hybrid (Laeliacattleya Tropical Sunset x Brassolaeliacattleya Chian T3Y Beauty). An in vivo test aimed at evaluating the efficacy of thiram and thiofanate methyl at concentrations of 0.05 g 100 mL-1 and 0.025 g 100 mL-1 respectively, in the control of rots caused by F. solani and B. ochroleuca was conducted. Nevertheless, the results of this experiment were not conclusive since none of the inoculated plants (including the positive controls without any fungicide treatment) developed disease symptoms. Another round of experiments aimed at evaluating in vivo control of the diseases will be conducted aimed at filling this blank of the work.