Margarida Goréte Ferreira do Carmo

Toxicidade de óleos essenciais de alho e casca de canela contra fungos do grupo Aspergillus flavus

Considering the inhibitory property of essential plant oils on the mycelial development of fungi, and the importance of Aspergillus flavus-like fungi which may produce aflatoxins, this research was designed to evaluate the toxicity of essential oils against fungi belonging to the group A. flavus isolated from peanut crops. The toxicity of eight essential oils against two isolates of A. Flavuslike fungi was evaluated in comparison to the synthetic fungicide benomyl. The toxicity of Cinnamomum zeilanicum Breym. and Allium sativum L. essential oils was also evaluated against 37 fungal isolates for a period of 12 months. The highest inhibition of the mycelial development of A. flavus was obtained with cinnamon and garlic essential oils. The inhibitory effect on growth was variable according to the fungal isolate.

Progresso da mancha-bacteriana do pimentão a partir de diferentes níveis iniciais de inóculo e do emprego ou não do controle com oxicloreto de cobre

O presente trabalho teve como objetivo avaliar o progresso da mancha-bacteriana do pimentao a partir de quatro quantidades iniciais de mudas infectadas (0; 3,3; 10 e 100%) associado a aplicacao semanal de oxicloreto de cobre (2,4 g de i.a./L de agua) ou nao. Foram conduzidos cinco ensaios, em condicoes de campo, em Seropedica (RJ), entre junho de 1996 e setembro de 1999. Quantificou-se a intensidade de doenca, regularmente, por meio de estimativas visuais da severidade da doenca (area foliar lesionada e desfolha) e calculou-se a area abaixo da curva de progresso da doenca normalizada (AACPD/ numero de dias). Estas foram submetidas a Analise de Variância (p=0,01) e a analise de regressao linear em funcao do logaritmo da quantidade inicial de mudas infectadas. A reducao do inoculo inicial teve efeito direto na quantidade final de doenca, e de forma mais marcante sob condicoes mais propicias ao desenvolvimento da doenca. A eficiencia do oxicloreto de cobre foi variavel e na maioria das vezes ineficiente, principalmente nos periodos mais propicios a epidemia, com reducao de sua eficiencia pela elevacao da temperatura.

Termoterapia via calor seco no tratamento de sementes de tomate: eficiência na erradicação de Xanthomonas campestris pv. vesicatoria e efeitos sobre a semente

Infected seed is the primary source of tomato (Lycopersicon esculentum) bacterial spot causing a rapid development of the disease with severe yield losses under favorable environmental conditions. The present work was undertaken to evaluate the effect of heat treatment (70 oC for 96 h) on germination and seed structure, as well as to determine the efficiency of heat therapy to prevent bacterial growth and disease establishment. Two experiments were carried out using tomato seeds inoculated by vacuum with Xanthomonas campestris pv. vesicatoria strain ENA 4463 adjusted to 107 cells.ml-1 followed by air-drying. In the first assay, four treatments were designed as follows: (1) inoculated seeds; (2) inoculation followed by heat treatment (70 oC/96 h); and two controls, uninoculated seeds without (3) and with (4) heat treatment. In the second assay, three treatments: (1), (2) and (3) were compared. Samples from different treatments were evaluated for the physiological status of the seeds and presence of the bacteria. The latter was tested by recovering the bacteria by vacuum extraction, isolation in semi-selective medium and visualizations though scanning electron microscopy (SEM). The efficiency of the heat treatment as a method to control the disease ranged from 99,96 to 100% for the second and first assay, respectively. Furthermore, there was no significant effect of the heat on seed germination. However, under SEM, heat treated seed showed some superficial structural changes, characterized by a greater number of broken trichomes, and a deposition of trichomes randomly or organized in plates over the seed surface and morphological changes in the bacterial cell shape.

Avaliação de cultivares de mandioca, para consumo in natura, quanto à resistência à mancha parda da folha

Evaluation of cassava cultivars for resistance to brown leaf spot Two field experiments were conducted to confirm the etiological agent of the cassava ‘brown leaf spot’, to study the progress of the disease and to evaluate resistance, agronomic and nutritional traits of different cassava cultivars. The experiments were performed in Rio de Janeiro State, Brazil. In the first experiment, six cassava cultivars (Amarelinha, Marcos OP, IAC-264, Baiana, Mantiqueira and Sonora), were evaluated from February/1997 to June/1998. In the second experiment, performed from January to August/1999, the same cultivars, plus ‘Saracura’, and ‘Rosada de SC‘ were evaluated, in a randomized complete block design, with three replicates. The intensity of the disease, initiated from natural infection, was quantified at seven and 15 days, when the severity and the incidence of injured leaves were considered. At harvest, the severity and incidence of injured leaves, defoliation rates and number of injured leaves were estimated. Disease progress curves were built for the incidence and for severity data; the area under the curves was used to calculate the disease severity and infected leaf severity. There were differences among the cultivars in relation to brown leaf spot resistance, caused by Cercosporidium henningsii. Cultivar ‘Amarelinha’ was the most susceptible, and ‘Baiana’ and ‘Sonora’ the most resistant. There were no differences between the cultivars in yield and root characteristics, except ‘Amarelinha’ with higher root weight. There was a negative and significant correlation between the severity of the disease (expressed by the values of the area under the disease progress curve) and the number and weight of roots.

Soil Factors Related to the Severity of Clubroot in Rio de Janeiro, Brazil

Soil pH and calcium levels are determining factors in the success or failure of managing clubroot during the cultivation of Brassica spp. The aim of the present study was to evaluate the influence of soil attributes in tropical regions on the development of roots and clubroot and the accumulation of biomass and nutrients in cauliflower. One hundred and fifty-one samples of soil and plants were collected from 16 family farms that have a history of more than 50 years of regular cauliflower cultivation in Nova Friburgo, Rio de Janeiro, Brazil. Chemical and physical analyses were performed on the soil samples, and the severity of clubroot and the accumulation of biomass and macronutrients in individual plants and plant tissues. Clustering and main principal component analyses were performed on the data. The disease occurred on all farms, but with different intensities. A direct relationship was observed for the soil attributes (acidity and exchangeable aluminum content in particular) with the percentage of roots with clubroot and with the accumulation of biomass and macronutrients in the different plant organs. To reduce losses from clubroot in weathered soils, practices should aim to reduce the pathogens inoculum potential and improve the physical and chemical conditions of the soil, which would favor root development of the plants.

Resistance in Capsicum spp. to anthracnose affected by different stages of fruit development during pre- and post-harvest

This study aimed to investigate the reaction of unripe and ripe fruits of Capsicum spp. accessions to Colletotrichum gloeosporioides during the pre- and post-harvest periods, and to identify sources of resistance for use in plant breeding programs. Thirty-seven Capsicum spp. accessions of the Universidade Estadual do Norte Fluminense Darcy Ribeiro were evaluated. They were cultivated in a greenhouse and arranged in a completely randomized design with five replications. Twenty fruits from each accession were inoculated at two stages (unripe and ripe) in two different environments (fruits inoculated in the plant and detached fruit inoculated under laboratory conditions). The symptoms were assessed every 24 hours between the 1st and 8th days after inoculation. There were highly significant differences in the values of the area under the disease progress curve and in severity, considering all sources of individual variation and their interactions. Values of low and moderate correlation were observed for inoculation of unripe and ripe fruit in both environments. These results indicate the existence of distinct genes responsible for resistance at different stages of fruit development. Complete lack of symptoms was registered only for accessions UENF 1718 and UENF 1797 (C. baccatum var. pendulum).

Inoculação e sobrevivência de Xanthomonas vesicatoria em sementes de tomateiro

The efficiency of six methods of Xanthomonas vesicatoria (Doidge) (9) inoculation on tomato seeds, and their effects on seed quality were tested : 1) vacuum inoculation with X. vesicatoria cell suspension in PB (0.005M, pH 7.4 e NaCl 0.85%); 2) immersion for 24 hours in with X. vesicatoria cell suspension and PB. 3) vacuum and saline solution in phosphate buffer; 4) immersion in PB for 24 hours; 5) seeds + ethanol; 6) control. Evaluations were performed for germination test and isolation in Modified Agar Nutrient (NAM)) at 1, 15, 30 and 45 days after treatments imposition. The moisture effect on the transmission of X. vesicatoria seeds inoculated under vacuum, followed or not by air drying at 30±1 oC, until 4% and 8% moisture were tested. Evaluations were performed as described above, after 24 hours and 30 days after the treatments. The methods of X. vesicatoria inoculation in tomato seeds can be used on routine analyses, however, inoculated seeds should be used until 30 days after inoculation. After this period, a large reduction on the recovery of viable cells occurs. The seed water content interferes with X. vesicatoria survival and transmission and explains the low percentages of X. vesicatoria recovery.

Efeito de produtos químicos e biológicos sobre a mancha bacteriana, flora microbiana no filoplano e produtividade de pimentão

The effect of weekly sprayings with streptomycin sulfate + oxytetracycline (0.8 g ia L-1), copper oxychloride (2.4 g ia L-1) and Agrobio fertilizer (5%) plus a control (water) was evaluated in the control of bacterial spot, the microbial flora in the phyloplan, and over yield in three bell pepper cultivars (Magda, Cascadura Itaipu and Magali R). The study was carried out under field conditions from May to December 2002. A randomized complete block experimental design was used with four replications in a 4 x 3 factorial design. Weekly assessments were made for plant height (cm); number of stems; total number of leaves; number of fallen leaves; number of leaves with visible symptoms; damaged leaf area (severity), and yield (t ha-1). The microbial population resident in the phyloplan and fruits was quantified at the same time. There was no effect of treatments on yield, but an effect was observed on plant growth, on leaf spot and on the microbial flora. Copper oxychloride inhibited plant development, reduced number of fallen leaves and decreased the bacterial flora. Agrobio stimulated plant growth and, like streptomycin sulfate + oxytetracycline, inhibited the bacterial population, except Bacillus sp., and fungi, except Cladosporium sp. in the phyloplan. Among the genotypes, the hybrid Magali R was significantly superior in plant vigor, yield and resistance to bacterial spot. The results suggest bactericidal activity of the Agrobio under field conditions.

Ação bacteriostática do biofertilizante Agrobio in vitro

Agrobio is a biofertilizer prepared from fresh cattle manure, water, molasses and minerals, fermented under room temperature in open containers during 56 days. This product has been widely used by organic and conventional farmers throughout Rio de Janeiro State, Brazil, to control several plant pathogens of various crops. The antibiotic effect of different concentrations of Agrobio against Xanthomonas euvesicatoria, in vitro vas evaluated. Four bioassays were performed with three isolates of the bacterium. Agrobio was tested in three preparation stages (35, 85 and 115 days of fermentation) and applied raw, filtered (0,22 µm) or autoclaved (120oC/20 minutes). The effect of the treatments was assessed by the diameter of the inhibition growth halo on Petri dishes. Agrobio presented bacteriostatic effect on X. euvesicatoria regardless of the sample age or pre-treatment. Growth inhibition occurred above 5% concentration, indicating the feasibility of Agrobio, as a bacterial leaf spot control agent, in early fermentation stages (35 days). Field experiments are necessary to confirm these results.

Post harvest decay of carrot caused by Ceratocystis fimbriata

Podridoes nas raizes de cenoura (Daucus carota L.) podem ocorrer em condicoes de campo devido a infeccao por Sclerotinia sclerotiorum (Lib.) de Bary ou Sclerotium rolfsii Sacc. ou pela bacteria Erwinia carotovora subsp. carotovora (Jones) Bergey et al. Perdas pos-colheita estao frequentemente associadas a Erwinia spp., principalmente quando as raizes sao colhidas em solos com alto teor de umidade e/ou, nao sao adequadamente secas apos a lavagem. No Rio de Janeiro, RJ, especialmente em mercados da Zona Oeste, foram observados sintomas de podridao de raizes de cenoura distintos daqueles citados na literatura. As lesoes se iniciavam em pequenos pontos e progrediam rapidamente culminando com podridao das raizes acompanhada de escurecimento da superficie das lesoes e formacao de cancros a medida que as raizes perdiam a turgescencia (Figura 1A,B). As primeiras constatacoes foram feitas em novembro de 2000 e se mantiveram em altos niveis ate marco de 2001, causando perdas de ate 40% por caixa. Amostras de raizes com os sintomas descritos foram levadas ao laboratorio na UFRRJ. Apos observacoes em microscopio estereoscopico e otico constataram-se conidios, clamidosporos e peritecios caracteristicos de Ceratocystis sp. Apos isolamento do fungo em BDA, efetuaram-se inoculacoes em raizes de cenoura, cv. Brasilia, recem colhidas, e em mudas de mangueira (Mangifera indica L.) a partir de cultura com dez dias de crescimento a 25°C. As raizes de cenoura foram inoculadas por meio de deposicao de discos de micelio com 4 mm de diâmetro sobre as raizes previamente feridas pela remocao de fragmentos do cortex e, por atomizacao de suspensao de conidios (2x104 conidios/ml) sobre raizes previamente feridas com escova de cerdas macias e sem ferimento. Em mangueira, os discos foram depositados sobre ramos jovens apos retirada da casca com auxilio de canivete. Simultaneamente, inocularam-se raizes de cenoura com discos de micelio de S. sclerotiorum e suspensao de celulas de E. carotovora subsp. carotovora. As raizes inoculadas, apos cinco dias de incubacao a 25 °C, reproduziram os mesmos sintomas inicialmente descritos e distintos daqueles resultantes da inoculacao com S. sclerotiorum e E. carotovora (Figura 1C). Nas raizes inoculadas por atomizacao observou-se desenvolvimento das lesoes de forma aleatoria na superficie das raizes previamente feridas enquanto que nas raizes sem ferimento as lesoes desenvolveram-se a partir dos pontos de emissao de raizes secundarias e de pequenas fissuras. As mudas de mangueira inoculadas igualmente desenvolveram sintomas de necrose na regiao inoculada e adjacencias. Observacoes em microscopio estereoscopico e otico evidenciaram a presenca das fases teliomorfica (peritecios globosos, escuros, ostiolado e com longo pescoco que termina com franjas de hifas ostiolares) e anamorfica (conidios enteroblasticos e clamidosporos globosos, marrons escuros) (Figura 1D, E e F) tipicos de Ceratocystis fimbriata Ell. e Haslt. (Wingfield e t a l . Ceratocystis and Ophiostoma , APS Press 1993). Este e o primeiro relato de ocorrencia de C. fimbriata em raizes de cenoura. FIG. 1 Inicio e progresso da podridao negra em raizes de cenoura (Daucus carota) (A) culminando com a formacao de cancros (B); testemunha sadia (C1), sintoma devido a inoculacao por Sclerotinia sclerotiorum (C2), por Ceratocystis fimbriata (C3), por Erwinia carotovora ssp. carotovora (C4), e devido a infeccao natural por C. fimbriata (C5); peritecio de C. fimbriata (D); formacao de clamidosporos (E) e conidios e clamidosporos da fase anamorfica de C. fimbriata.(F). 02085 Post harvest decay of carrot caused by Ceratocystis fimbriata The occurrence of post harvest decay on carrot (Daucus carotae) caused by Ceratocystis fimbriata is reported for the first