Sylvia Dias Guzzo

Promoção de crescimento e indução de resistência à antracnose por Trichoderma spp. em pepineiro

The objective of this work was to determine the effect of 60 isolates of Trichoderma and the product Trichodermil on the growth promotion and on the induction of systemic resistance to anthracnose caused by Colletotrichum lagenarium in cucumber, and to identify isolates of Trichoderma spp. effective as resistance inductors. In the assays of growth promotion, the Trichoderma spp. isolates were inoculated in the substrate and, after 21 days, the shoot dry weight of the plants was measured. In the experiments of resistance induction, the isolates which promoted growth were inoculated in the substrate, at the base of the plants, seven days before C. lagenarium inoculation in the leaves. The isolate which showed the best performance was evaluated for anthracnose symptom reduction in applications at 3, 7 or 14 days before the pathogen inoculation, and for its ability of increasing the peroxidase activity. Nineteen isolates and Trichodermil promoted cucumber growth up to 100% and conferred plant protection against anthracnose up to 88.39%. The isolate IB 31/06 reduced the disease severity at the evaluated time intervals. No significant peroxidase increase was observed seven days after treatment with IB 31/06, in the plants treated and infected with the pathogen, in comparison to infected plants. Gene sequencing of the 19 isolates allowed for the identification of seven Trichoderma different species.

Induced resistance against Xanthomonas axonopodis pv. passiflorae in passion fruit plants

Control of bacterial leaf spot of yellow passion fruit using the abiotic resistance inducer, acibenzolar-S-methyl (ASM), and the biotic agents, harpin protein and glycoproteins extracted from two Xanthomonas species, was evaluated. The inducers were applied by spraying the leaves 72 h before the inoculation with Xanthomonas axonopodis pv. passiflorae. The inducers were also applied by seed immersion and the inoculation was performed when the seedlings had four true leaves. The results showed that ASM conferred a protection up to 70% at the concentration of 12.5 µg a.i. mL-1, while harpin led to an increase in bacterial symptoms. The glycoproteins from Xanthomonas spp. conferred up to 72% protection in plants against the bacterium. ASM or harpin provided up to 90% and 47% protection, respectively, in yellow passion fruit seedlings raised from treated seeds. Thus, leaf treatment with ASM or the glycoproteins from Xanthomonas spp. and seed treatment with ASM or harpin are potent inducers of resistance in passion fruit plants against X. axonopodis pv. passiflorae.

Proteção do cafeeiro contra cercosporiose por acibenzolar-S-metil e proteína harpina

The objective of this work was to evaluate the protective effect of harpin protein and acibenzolar-S-methyl (ASM) against brown eye spot, in coffee plants, and its effect on in vitro conidial germination and mycelial growth of Cercospora coffeicola. In the first assay, plants treated with ASM (25, 50, 100, 200 µg mL -1 ) received the inoculum of a C. coffeicola conidial suspension, and the disease severity was evaluated 30 and 60 days after inoculation. In the second assay, plants were sprayed with harpin (7.5, 15, 30, 60, 120 µg mL -1 ) following the same procedure. In a third trial, plants previously sprayed with ASM (200 µg mL -1 ) or harpin (15 µg mL -1 ) were treated again with these products 30 days after pathogen inoculation. ASM and harpin protected the coffe plants against brown eye spot 30 days after inoculation with C. coffeicola. However, 60 days after inoculation, only ASM (200 µg mL -1 ), with one or two applications, conferred protection to plants against C. coffeicola. Coffee plants were protected against cercosporiosis, when harpin was reapplied on plants 30 days after a previous treatment with this protein. Harpin and acibenzolar-S-methyl did not inhibit the in vitro conidial germination and the mycelial growth of the pathogen.

Efeito da chuva sobre a tenacidade e eficiência de fungicidas cúpricos associados ao óleo vegetal no controle da ferrugem do cafeeiro

This work was carried out to verify the effect of precipitation on different copper fungicides application and its efficiency for controling coffee (Coffea arabica) rust caused by Hemileia vastatrix, in the presence or absence of vegetable oil. Cuprous oxide, hydroxide of copper and copper oxicloride, in the proportion of 0.3% of the active ingredient, were sprayed on coffee plants 24 h before inoculation with urediniospores. 60 min after spraying, half of the plants received 20 mm of rain for 6 min; repeated four times at weekly intervals. The other half of the plants did not receive water. Cuprous oxide was more efficient without oil than with oil, contrasting with the results obtained for hydroxide of copper. Adding oil did not improve copper oxicloride action. Rain was not observed to make any significant difference in the incidence and severity of coffee rust among the plants. This suggests that, besides copper compounds being contact products, they showed a certain resistance to the action of the rain, with good characteristics of adherence and/or persistence on the surface of the coffee leaves. The mixture of copper oxicloride with oil, independent of the presence of rain, was efficient in reducing the viability of the spores to 13.5%, indicating the erradication action of this treatment, while the test treatment showed 41.29%. Cuprous oxide with no oil in the absence of the rain also provided no sporulation action, but did not differ from the test plots where rain was present.

Promoção do crescimento do feijoeiro e controle da antracnose por Trichoderma spp.

The objective of this work was to evaluate the ability of Trichoderma spp. to promote growth of common bean plants and to reduce severity of anthracnose (Colletotrichum lindemuthianum), as well as to identify the best performing isolates. Sixty Trichoderma spp. isolates were evaluated as to their capacity to promote growth in common bean. The seven isolates that stood out were added to the culture substrate and assessed for reduction in severity of anthracnose in bean plants treated with C. lindemuthianum conidia. The most efficient isolates in controlling the disease were identified by DNA sequencing. The IB 28/07 isolate was evaluated in the concentrations 0.5, 1, 1.5, and 2% (weight:volume), which reduced disease severity in 41.51, 55.15, 81.82, and 96.06%, respectively. The most efficient Trichoderma spp. isolates can promote increases above 30% in dry matter production and reduce disease severity between 63 and 98%. These isolates were identified as belonging to the species Trichoderma harzianum, T. strigosum, and T. theobromicola.

Redução dos sintomas causados pela Xylella fastidiosa subsp. pauca por meio de aplicação de benzotiadiazole e silício

O objetivo deste trabalho foi avaliar o efeito da aplicacao do benzotiadiazole (BTH) e do silicio sobre o controle da doenca causada pela Xylella fastidiosa subsp. pauca em Nicotiana tabacum. Os experimentos foram conduzidos em condicoes de casa de vegetacao, onde as plantas de N. tabacum receberam inoculacao de X. fastidiosa (linhagem 9a5c) com 4,7x107 UFC mL-1. Os tratamentos consistiram da pulverizacao das folhas, com solucoes de BTH (0,6 e 1,2 mM), e aplicacao ao solo de solucoes de metassilicato de sodio (2 e 4 µM de Si). Cinco plantas foram utilizadas, por tratamento. Plantas de N. tabacum tratadas com BTH nao demonstraram reducao de sintomas da bacteriose. Entretanto, plantas tratadas com metassilicato de sodio, sim. A inducao de resistencia pelo Si podera ser util no controle da clorose variegada dos citros.