The production and distribution of the phytoalexin falcarindiol in tomato foliage infected with leaf mold was examined to determine how the fungus Cladosporium fulvum is able to colonize and sporulate in an apparently antifungal environment. In a compatible interaction (cv. Potentate – C. fulvum race 2.3), by 12 and 15 days after inoculation, solvent-extractable falcarindiol and two other phytoalexins from tomato, compound 2 (probably falcarinol) and compound 3 (unidentified), reached concentrations considerably in excess of ED50 values for inhibition of the fungus. In contrast, intercellular (apoplastic) fluids obtained from similarly infected leaflets contained only traces of falcarindiol. ED50 values for germination and germ-tube growth of C. fulvum increased as the incubation time was extended, suggesting that adaptation or recovery was possible at the concentrations tested. In in vitro experiments, C. fulvum appeared to readily metabolize falcarindiol, as did a Lycopersicon cell suspension culture. Binding of falcarindiol to living and dead fungal and plant cells was also observed. Falcarindiol, injected into tomato leaflets, decreased rapidly and was only recovered in trace amounts by 24 h. The results suggest that falcarindiol and probably the two other phytoalexins do not reach sufficient concentrations in the apoplast of an infected susceptible leaf to have an effect on growth and sporulation of C. fulvum. Key words: leaf mold, Fulvia fulva, falcarindiol, falcarinol.
Gray mold of roses (Rosa hibrida) caused by Botrytis cinerea requires many management strategies for its control. The effect of pulsing rose cv. Kiss with solutions of citric acid, salicylic acid, sucrose, calcium sulfate, and silver thiosulfate (STS) on disease severity and vase life of the flowers was evaluated. The solutions were applied to cut stems at different stages of harvest, the variation in the opening stage of harvest did not affect the results. Pulsing with STS reduced the values of area under the disease progress curve (AUDPC) and of severity of disease by 15% and 55%, respectively, and increased the vase life of the flowers by 20%. Calcium sulfate consistently reduced AUDPC by 66% and maximum severity by 88%, and increased vase life of the flowers by 37%. Therefore, pulsing rose buds with solutions of STS and calcium sulfate is potentially useful in reducing losses due to gray mold after harvest and in extending the vase life.
Este trabalho objetivou testar a eficiência da hidroterapia e de alguns fungicidas no controle da antracnose causada por Colletotrichum musae e verificar o seu efeito na evolução da cor de frutos de banana (Musa spp.) 'Prata'. Buquês foram atomizados com C. musae (2,5 x 10(6) esporos/ml em água) e imersos 24 h depois em água a 45 ºC, 50 ºC e 53 ºC, durante 0, 10, 15 e 20 min. Outros buquês foram imersos por 3 min nos fungicidas tebuconazole, procloraz, difenoconazole e propiconazole nas doses de 0, 62,5, 100, 125 e 250 mg.l-1. Nos frutos tratados a 45 ºC por 20 min (5, 10 ou 15 min foram ineficientes) a incidência da doença foi de um fruto infetado por buquê. A exposição dos frutos a 50 ºC por 20 min reduziu a área lesionada em 85% e a 53 ºC por 15 e 20 min, os frutos apresentaram uma área lesionada de aproximadamente 3% e 0%, respectivamente. Frutos não tratados apresentavam 53% da área lesionada aos 12 dias de armazenamento. Os fungicidas procloraz em doses de 100, 125 e 250 mg.l-1, e propiconazole a 250 mg.l-1 foram os mais eficientes no controle da doença. Os frutos estavam sadios após 15 dias de armazenamento, enquanto que a testemunha apresentava aproximadamente 60% da área do fruto lesionada. Em armazenamentos de até 12 dias, o fungicida tebuconazole a 250 mg.l-1, procloraz a 62,5 mg.l-1 e propiconazole a 62,5, 100 e 125 mg.l-1 reduziram a área lesionada dos frutos para 1 a 3%. O fungicida difenoconazole foi ineficiente no controle da antracnose.
The number of pustules per leaf area, the average diameters of pustules and average spore production and spore viability were determined on fully expanded primary leaves of dry bean (Phaseolus vulgaris) which had been treated with a suspension of 106 cells of Bacillus subtilis. either as culture broth or as lyophilized broth, 24, 48, 72, 96 or 120 h before inoculation with urediniospores of Uromyces appendiculatus. Urediniospores were collected from treated plants, inoculated to new plants and the number of pustules per leaf area determined. The number of pustules per leaf, spore production per leaf area and the viability of spores were all significantly reduced by previous application of either liquid cultures or lyophilized broth, with greater reductions occurring at shorter intervals before inoculation with U. appendiculatus. There was no effect of treatment on the diameter of pustules. This reduction of disease severity could be of significance in the production of grown beans.
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