Sérgio Florentino Pascholati

Efeito de Saccharomyces cerevisiae na produtividade de sorgo e na severidade de doenças foliares no campo

Saccharomyces cerevisiae e uma levedura com potencial para o controle de doencas de plantas, pois apresenta a capacidade de sintetizar compostos antibioticos, habilidade de competicao por espaco e nutrientes no filoplano de muitas especies vegetais, alem de possuir elicitores na parede celular. O presente trabalho teve como objetivos avaliar a produtividade de duas cultivares de sorgo (Sorghum bicolor) tratadas com a levedura, e verificar o controle da antracnose, causada por Colletotrichum sublineolum e da mancha foliar, provocada por Exserohilum turcicum. Os experimentos foram conduzidos em campo, em um delineamento de blocos ao acaso, com sete tratamentos e quatro repeticoes. Aplicacoes semanais de S. cerevisiae (Fermento Biologico Fleischmann - 25 mg/ml) reduziram significativamente a antracnose em sorgo cv. Tx-398B e melhoraram a produtividade da mesma. Na cv. 910753, uma unica aplicacao com a levedura foi suficiente para reduzir o progresso da mancha foliar, porem a produtividade nao foi elevada por qualquer um dos tratamentos. Conclui-se que S. cerevisiae apresenta um bom desempenho no campo para o controle de doencas foliares em sorgo, melhorando ou nao comprometendo a produtividade da cultura, na dependencia da cultivar utilizada.

Effect of acibenzolar-S-methyl and Saccharomyces cerevisiae on the activation of Eucalyptus defences against rust

Tree defence mechanisms against the fungus Puccinia psidii were examined by comparing the activities of defence-related enzymes (chitinase, peroxidase and phenylalanine ammonia-lyase) of two Eucalyptus grandis × E. urophylla (urograndis) hybrids, previously classified as either susceptible to rust (VR hybrid) or moderately resistant to rust (C0 hybrid). Furthermore, the potential of disease control by artificial activation of host defences using either acibenzolar-S-methyl (ASM) or Saccharomyces cerevisiae extract was also investigated. Greenhouse inoculation trials revealed that the C0 hybrid had lower disease severity than the VR hybrid but following foliar applications of either ASM or S. cerevisiae extract treatment, disease severity (evaluated at 15 days after inoculation) was reduced in both hybrids. This enhanced resistance was associated with the induction of a hypersensitive reaction which appeared to be effective in controlling rust in both clones. The activity of all enzymes differed between clones and inducer treatment. The role of the defence-related enzymes in imparting resistance to eucalypt hybrids against rust is discussed.

Proteomic response of the phytopathogen Phyllosticta citricarpa to antimicrobial volatile organic compounds from Saccharomyces cerevisiae

Volatile organic compounds (VOCs) released by Saccharomyces cerevisiae inhibit plant pathogens, including the filamentous fungus Phyllosticta citricarpa, causal agent of citrus black spot. VOCs mediate relevant interactions between organisms in nature, and antimicrobial VOCs are promising, environmentally safer fumigants to control phytopathogens. As the mechanisms by which VOCs inhibit microorganisms are not well characterized, we evaluated the proteomic response in P. citricarpa after exposure for 12h to a reconstituted mixture of VOCs (alcohols and esters) originally identified in S. cerevisiae. Total protein was extracted and separated by 2D-PAGE, and differentially expressed proteins were identified by LC-MS/MS. About 600 proteins were detected, of which 29 were downregulated and 11 were upregulated. These proteins are involved in metabolism, genetic information processing, cellular processes, and transport. Enzymes related to energy-generating pathways, particularly glycolysis and the tricarboxylic acid cycle, were the most strongly affected. Thus, the data indicate that antimicrobial VOCs interfere with essential metabolic pathways in P. citricarpa to prevent fungal growth.

EFEITO DAS CIANOBACTÉRIAS Synechococcus leopoliensis E Nostoc sp. SOBRE Colletotrichum sublineolum E NA INTERAÇÃO DO PATÓGENO COM PLANTAS DE SORGO

Among the pathogens that cause damage to sorghum (Sorghum bicolor), Colletotrichum sublineolum, the causal agent of anthracnose, is one of the major problems. In trying to find alternative ways to control the disease, the effect of two cyanobacteria, Synechococcus leopoliensis and Nostoc sp., was tested on fungal development in vitro and on the protection of sorghum plants kept under greenhouse conditions. Filtrates from both cyanobacteria improved conidium germination in assays carried out on glass slides covered with polystyrene. The in vitro mycelial growth of the pathogen was stimulated by S. leopoliensis too. The cyanobacteria did not induce the accumulation of phytoalexins in etiolated sorghum mesocotyls. The protection of a susceptible sorghum cultivar, with six true leaves, was low and only observed when the cyanobacterium treatments were applied twice before the inoculation of the plants with the pathogen. The stimulation effect of the cyanobacteria on C. sublineolum was likely due to nutrients present in the cyanobacteria culture filtrates. The low level of antracnose control may be explained by the low cyanobacterial capacity to produce fungal inhibitory compounds or to induce an important resistance response in the plants, such as, the phytoalexin accumulation. Therefore, based upon this work, S. leopoliensis and Nostoc sp. did not exhibit potential as biological control agents of C. sublineolum in sorghum.

Effect of Ascophyllum nodosum seaweed extract on post-harvest 'Tommy Atkins’ mangoes

The aim of this study was to determine the effect of Ascophyllum nodosum extract (AN), applied in different doses on the physicochemical characteristics of post-harvest ‘Tommy Atkins’ mangoes. The selected mango fruits were treated with different extract concentrations (0%, 0.1%, 0.3%, 0.5% and 1.0%) and stored for 12 days at 25±2 °C and 75±5% RH. Every 3 days, fruit mass loss (PM), color angle (Hue) (AH), firmness, pH, titratable acidity (AT), content of total soluble solids in pulp (°Brix) and content of carbohydrates in shell were assessed. The experiments were carried out in CRD in a 5 x 5 factorial arrangement (concentrations x days of storage) with four replications. AN was effective in preventing PM, with a reduction of up to 40.2%, as observed at concentration 0.1% compared to control. There were no differences among concentrations on AH, however, all of them differed significantly from control with higher AH, especially on the 12nd day. Fruit firmness was lower in control, the pH increased with the storage time and AT decreased. For all these parameters, mangoes treated with the extract differed from control. The pulp sample °Brix increased with the storage time as well as the content of reducing sugars, with consequent reduction of non-reducing sugars in fruit shell. These tests indicate the possibility of using AN as an alternative management in preserving mangoes in the post-harvest stage.

Bio- and Chemicalcontrol of Sclerotinia sclerotiorum using Stachybotrys levispora and its secondary metabolite griseofulvin

Sclerotinia sclerotiorum is responsible for the white mold of soybeans, and the difficulty to control the disease in Brazil is causing million-dollar damages. Stachybotrys levispora has shown activity against S. sclerotiorum. In our present investigation, we analyzed the chemical basis of this inhibition. Eight compounds were isolated, and using spectroscopic methods, we identified their structures as the known substances 7-dechlorogriseofulvin, 7-dechlorodehydrogriseofulvin, griseofulvin, dehydrogriseofulvin, 3,13-dihydroxy-5,9,11-trimethoxy-1-methylbenzophenone, griseophenone A, 13-hydroxy-3,5,9,11-tetramethoxy-1-methylbenzophenone, and 12-chloro-13-hydroxy-3,5,9,11-tetramethoxy-1-methylbenzophenone. Griseofulvin inhibited the mycelial growth of S. sclerotiorum at 2 μg mL-1. Thus, the antagonistic effect of S. levispora to S. sclerotiorum may well be due to the presence of griseofulvins. Our results stimulate new work on the biosynthesis of griseofulvins, to locate genes that encode key enzymes in these routes and use them to increase the production of these compounds and thus potentiate the fungicide effect of this fungus. S. levispora represents an agent for biocontrol, and griseofulvin represents a fungicide to S. sclerotiorum.