Effect of doses of fungicides and plant resistance activators on the control of Rhizoctonia foliar blight of soybean, and on Rhizoctonia solani AG1-IA in vitro development

Rhizoctonia foliar blight (RFB) of soybean [Glycine max (L.) Merrill] occurs in many tropical and subtropical regions, causing yield reductions of up to 70% and in Brazil, up to 60%. The disease is caused by Rhizoetonia solani AG1-IA and AG1-IB, and by AG2-3 in Japan. RFB occurs in the North, Northeast and Mid-west regions of Brazil. Chemical control remains the only effective method of controlling RFB, but its efficiency depends upon environmental conditions. In this study, 18 fungicides, salicylic acid (SA) and acibenzolar-s-methyl (ASM) were evaluated on R. solani AG1-IA in vitro, by mycelial growth rating and estimating effective concentration for 50% (EC 50) and 90% (EC 90) inhibition of mycelial growth, and in vivo by reduction of disease severity on soybean plants in greenhouse conditions. Mycelial growth was strongly inhibited by the fungicides pyraclostrobin + boscalid and fludioxonil. Preventive fungicide applications were the most effective. Strobilurins were more efficient both in preventive and curative applications. Best results with plant resistance activators were obtained with SA (2.5 mM) sprayed at 20 d before inoculation and with ASM (12.5 mg a.i. l(-1)) 10 d before inoculation. (c) 2005 Elsevier Ltd. All rights reserved.

Avaliação dos efeitos de doses de triadimenol e de tebuconazole sobre o crescimento do mesocótilo em plântulas de trigo

Wheat (Triticum aestivum L.), Anahuac cultivar, were treated with six triadimenol (0,0; 12,5; 25,0; 37,5; 50,0 and 62,5 g of a.i./100 kg of seeds) and tebuconazole (0,0; 7,5; 15,0; 22,5 30,0 and 37,5 g of a.i./100 kg of seeds) dosis to reduce the subcrown internode length and then to deep the point of emission of adventitious roots. Seeds were seeded in pots with soil, with 5 cm of depth and after two weeks the seedlings number was counted and the subcrown internode length (CM) was evaluated. The CM may be represented by the equations: a) CM = 4,49 - 0,1779 x + 0,002161 x2 (r2 = 0,9247); b) CM = 4,62 - 0,29948 y + 0,006480 y3 - 0,00004622 y3 (r2 = 0,9551), where ''x'' and ''y'' represent tebuconazole and triadimenol dosis, respectively. The CM showed minimum values for triadimenol dosis equal to or higher than 37,5 g a.i./100 kg of seeds and for tebuconazole decreased continuously with the increase of the product dosis, showing values near to 1 cm for the maximum dosis. The triadimenol allowed, at suitable dosis, almost total inhibition of the wheat seedlings subcrown internode with no effects on seedling emergence and initial growth.

Níveis de sódio e potássio séricos de caprinos confinados e em pastoreio

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Potentiation of panic-like behaviors of the rat by subconvulsive doses of strychnine

The present study was carried out to determine possible panicogenic effects of strychnine administered in subconvulsive doses to rats. Two experiments were conducted to assess two major features of panic in animal models: panic-related flight (through the observation of wild running [WR]) and defensive fights. In the first one, 20 adult male Wistar rats were injected with six different doses of strychnine ranging from 0.5 to 4.0 mg/kg. After 15 min of free observation, the animals were submitted to high-intensity acoustic stimulation and the incidence of WR was recorded. Higher doses of strychnine (above 2.5 mg/kg) easily evoked seizures, but lower doses raised the incidence of WR in a dose-dependent manner. The most effective dose for WR (1.5 mg/kg) was used in the second experiment, in which we investigated the effects of strychnine on sleep-deprivation-induced fights (SDIFs) that have defensive characteristics. For this purpose, 40 subjects were submitted to 5 days of REM-sleep deprivation by the single-platform method and were then assigned into two groups, i.e., strychnine vs. control. After the injections, the animals were observed in social groupings for SDIF recordings over a period of 60 min. The strychnine-treated groups had more SDIF than the control groups (P<.05, Mann-Whitney U test). We conclude that the high level of neural excitability promoted by partial blockade of the glycinergic system can contribute to the manifestation of panic reactions. (C) 2003 Elsevier B.V. All rights reserved.

Produtividade e qualidade de frutos do mamoeiro em função de tipos e doses de biofertilizantes

Biofertilizers are organic products usually obtained from an anaerobic process, evaluated mainly as phytoprotectors for agriculture, although they can improve fruit production. By this way, a field experiment was carried out in Remigio County, Paraiba State, Brazil, to evaluate the effects of two bovine biofertilizers on yield, medium mass and quality of papaya fruits (Carica papaya L.), 'Baixinho de Santa Amalia cultivar. Treatments were distributed in a randomized complete blocks design with three replications and 15 plants in each parcel, in a 2 x 5 factorial arrangement, with two biofertilizers: simple (water and fresh bovine manure) and supermagro (water, fresh bovine manure, macro and micronutrients and a protein mix), applied in soil under liquid form at five volumes, as follows: 0.0; 0.5; 1.0; 1.5; e 2.0 L cave(-1). There was no statistical difference between biofertilizers for fruit mass, yield and external and internal fruit quality variables, while between volumes differences were registered for both biofertilizers. The results, except for fruit firmness, registered positive effects of the biofertilizers on 'Baixinho de Santa Amalia' papaya cultivar in relation to yield and physical and chemical fruit quality.

Dinâmica do potássio no solo e nutrição potássica da soja

Potassium deficiency in soybeans has spread iii São Paulo State, Brazil, as a consequence of soil K reserve depletion. Exchangeable and nonexchangeable K dynamics in soil were investigated in order to understand the reserve exaustion and its significance to soybean nutrition. Soybean was grown in 8 1 pots with five soils differing in K and clay contents, in presence or absence of K fertilization. Soil samples were taken at 20 days interval and soybean was harvest at R6. Exchangeable (H2SO4 0,05 N) and nonexchangeable K (boiling HNO3) were estimated in soil sample. Two of the soils were very poor in exchangeable K, and even so there was no response in dry matter due to K fertilization. In spite of some differences in K contents in some of the soybeans parts, generally K absorption was not affected by K fertilization, except in grains. Potassium acumulation in soybean plants were affected by soils, but the response was not closely related to exchangeable K in soil. The main K source to the plants was the HNO3 extrated K, showing that this form is not at all nonexchangeable. After the period of maximum plant demand there was a sharp increase in extractable K in soil showing a tendency to a natural equilibrium.

Análise genética da concentração de potássio eritrocitário em bovinos

Red-cell potassium concentration was determined in five breeds of cattle: Brown Swiss, Nelore, Pitangueiras, Gir and Girolanda. All the cattle examined for the red cell potassium concentration presented low potassium concentration or LK type. This were divided in the following sub-types: low-low potassium concentration (LLK variation: 7.0 -15.9 m-equiv/l) in 16.9% of the animals; medium-low potassium concentration (MLK variation: 16.0 - 30.9 m-equiv/l) in 77% of animals and high-low potassium concentration (HLK variation: 31.0 - 50.0 m-equiv/l) in 6.1% of the animals. This results may be associated with a tropical environment because animals whith red-cell potassium concentration have advantage in this environment.

Male gonadal denervation by guanethidine at pre-puberty: Different doses, different results. The intervention of the pineal deafferentation

Since gonadal denervation and pineal deafferentation by cervical superior ganglionectomy affect sexual development, this study was performed to evaluate testicular steroidogenesis, spermatogenesis and the cervical superior ganglion (CSG) histology in rats treated with guanethidine (GD). The treatment was performed by GD s.c. injections for 3 weeks, from the 21st day of age to the 41st day of age (pre-puberty), when the animals were sacrificed. Different doses were used: group A=10 mg/kg/day, group B=50 mg/kg/day and saline (control group). Testicular denervation was confirmed by HPLC for catecholamines in testicular tissue. Testicular concentrations (TC) of progesterone (P4) and testosterone (T) were measured by RIA. Significantly higher TC of P4 and lower TC of T were observed only in group A in comparison with group B and the control group. No alteration of sperm production was observed in either treated group. Histological analysis of CSG showed only few neuronal alterations in group A rats, while in group B the nervous cells were practically destroyed. This suggests that 10 mg/kg/day GD treatment probably produces a specific blockade of 17 alpha-hydroxylase/17,20 desmolase at pre-puberty leading to a decrease of the androgen production. However, in the 50 mg/kg/day group no differences were observed concerning the steroid profiles, this result being attributed to the extensive damage to the CSG observed only in group B. The CSG destruction causes deafferentation of the pineal gland producing abolishment of the inhibition of the 17 alpha-hydroxylase/17,20 desmolase promoted by melatonin or by an out of phase production of androgen.

Gas exchange in lisianthus plants (Eustoma grandiflorum) submitted to different doses of nitrogen

The effect of different doses of nitrogen (N) on gas exchange, relative chlorophyll (Chl) amount, and the content of N in the aerial biomass of lisianthus was evaluated. The treatments consisted of six different concentrations of N (50, 100, 150, 200, 250, and 300 g m(-3) noted as N-50, N-100, N-150, N-200, N-250, and N-300, respectively), applied through the fertirrigation technique. N-250 and N-300 induced increase in the contents of foliar Chl and N in the aerial biomass, that in turn contributed to an increase of photosynthetic activity in lisianthus.

Adubação potássica da soja em latossolo vermelho-escuro fase arenosa

Durante três anos foi conduzido um experimento em Latossolo Vermelho-Escuro fase arenosa, no qual foram estudados os efeitos de adubações anuais com 0,40, 80, 160 e 240 kg/ha de K2O, nas formas de cloreto de potássio e sulfato de potássio, aplicados no sulco de semeadura ou em área total com incorporação. Observou-se resposta à adubação potássica a partir do segundo ano de cultivo. As máximas produções sempre estiveram associadas a teores de potássio nas folhas acima de 1,5%. Em anos mais secos que o normal, as aplicações a lanço proporcionaram melhores resultados do que as aplicações em sulcos. Não foram observadas diferenças entre as fontes de potássio utilizadas. Notou-se acentuado decréscimo nos teores de potássio trocável do solo, com o transcorrer do tempo, sendo necessária a aplicação de doses maiores que 80 kg/ha de K2O por ano para manter o nível original. Por outro lado, a aplicação de doses elevadas de potássio levou a uma perda significativa do nutriente por lixiviação.

Diferentes resposta de cutivares de soja e potássio

Soybean (Glycine max (L.) Merrill) is known to have a high ability as a potassium extractor, and different cultivars show different potassium requirements. An experiment was run to study the potassium nutrition of soybean as related to plant characteristics. Six soybean cultivars (FT-2, Bossier, IAC-11, IAC-17, IAC-18 and IAC-19) were grown in 6 kg pots filled with the topsoil of a Dark Red Latosol (sandy loam), either with and without K fertilization. The plants were harvested 70 days after emergence. Soybean response to potassium was not related to growth habit or group of maturation. There was a different response to K. The cultivars IAC-18 and FT-2 were less tolerant to K deficiency. Potassium deficiency in the leaves was not related to top dry matter production. With K fertilization soybean plants showed small root volume and higher ratio canopy/root. With high K in soil, all of the cultivars showed higher nodulation.