Potassium nutrition and frost tolerance of potato genotypes

Six potato genotypes were tested to evaluate the effect of K nutrition on frost tolerance by measuring electrolyte leakage from leaves exposed to various freezing temperatures. Potato genotypes were selected through the known range of low temperature survival tolerance within tuber‐bearing Solanum species. An experiment was conducted using a soil high in K; and then nutrient solution experiments were conducted in the open environments of La Molina. Commercial K fertilizers, at different levels, were unable to increase significantly the frost tolerance in a common potato cultivar grown in a soil high in K. In nutrient solutions experiments, with plants grown without any hardening process, we found that there is a genetically related capacity to respond through K nutrition to increase frost tolerance among potatoes. The common commercial potato, S. tuberosum, did not change significantly its freezing sensitivity when K nutrition was varied. But S. curtilobum, which is grown by low income farmers in the Titicaca Lake area of Bolivia and Peru, especially reduced its sensitivity to frost tolerance when submitted to K deficiency by as much as 1.5 to 2°C. Leaf free proline does not accumulate as a result of K deficiency but all the K deficient plants had lower amounts of free proline. The K deficient plants also showed a lower induced nitrate reductase activity.     

Effect of increased cobalt treatments on cobalt concentration and growth of tomato plants

An experiment developed in soilless culture was used to study the effect of several levels of Co²⁺ (0, 5, 15, and 30 mg L^‐1 ) on the growth of tomato plants (Lycopersicon esculentum M. cv. Ramy). Absorption, transport, and accumulation of this metal in roots, stems, leaves, and fruits were also studied. Uptake was increased by application of this metal concentration in the nutrient solution, efficiency of root uptake of cobalt decreased with increased Co²⁺ treatment in the soilless culture system. The translocation of Co²⁺ from roots to aerial vegetative parts was increased with the time of experiment and Co²⁺ concentration in the nutrient solution. The presence of this metal in nutrient solution reduced tomato leaf production and elongation, specially at higher treatments.     

Cadmium accumulation and distribution in cucumber plant

An experiment developed in soilless culture was used to study the cadmium (Cd) accumulation, and distribution of Cd in cucumber (Cucumis sativus var. peonero‐mixfl) plant. Four treatments were established (0, 5, 10, and 20 mg Cd⁺² L^‐1). Uptake, and transport of Cd were increased with time, and Cd concentration in the nutrient solution. Fruit accumulation of Cd varied from 16 to 92 mg kg^‐1 depending on the treatments. The fresh weight, and dry matter accumulation of cucumber plant organs (roots, stem, leaves, and fruits) was affected by cadmium treatment. A decrease of the total, a, and b chlorophyll increasing Cd concentration in nutrient solution, and time of experiment were observed. The incidence of this metal on the content of chlorophyll b seem to be faster than chlorophyll a. Cucumber plant could be a feasible plant for pollution experiments due to their high sensibility, and transport efficiency.     

Reuse of tertiary municipal wastewater effluent for irrigation of Cucumis melo L.

The reuse of tertiary wastewater for crop irrigation presents itself as an alternative to the scarcity of quality water suffered by many countries in the Mediterranean region. Furthermore, this resource can provide an important saving of fertilizers as well as benefits to the environment, as it avoids the discharge of contaminated water into public waterways. This study focuses on the effect of irrigation with ozonized wastewater on the melon crop. In this study, melon crops were irrigated with either ozonized wastewater or ground water commonly used in the agricultural area (control treatment). Fertigation, by means of drip irrigation, was delivered according to the crop’s needs, evaluating the fertilizers contributed by each of the waters and that added in mineral form. Throughout the crop’s development, the characteristics of the water, soil and plant (leaf and fruit) were studied from a chemical, physicochemical and microbiological perspective. The results obtained show that irrigation with ozonized wastewater, in these conditions of crop growth, produces similar effects as ground water on the soil properties, on the concentration of macroelements in the leaf and fruit and on the yield of melon fruit. Furthermore, the reuse of this effluent leads to a greater saving in nitrogenous and potassium fertilizers compared to fertigation of the crop with ground water.     

Effect of corn distillers dried grains with solubles on growth performance and health status indicators in weanling pigs

Two experiments were conducted to evaluate effects of corn distillers dried grains with solubles (DDGS) on growth performance and health status of weanling pigs. Experiment 1 evaluated effects of increasing concentrations of DDGS on growth performance and health of weanling pigs. Dietary treatments included 1) control (CTL), 2) 0% DDGS (0% DDGS in phase 2 and 30% DDGS in phase 3), 3) 5% DDGS (5% DDGS in phase 2 and 30% DDGS in phase 3), and 4) 30% DDGS (phases 2 and 3). Overall, pigs fed 30% DDGS during phases 2 and 3 had decreased (22.1 vs. 25.1 and 24.0 kg; P = 0.003) BW compared with CTL pigs and pigs that only received DDGS during phase 3. In addition, pigs fed 5 or 30% DDGS in phase 2 had decreased (422.7 or 390.0 vs. 468.2 g; P = 0.003) ADG compared with CTL pigs. However, pigs fed 0% DDGS during phase 2 had similar BW, ADG, and ADFI compared with CTL pigs. Experiment 2 was conducted to evaluate effects of DDGS, lactose, and their interaction on growth performance and health of weanling pigs. Dietary treatments included 1) CTL, 2) lactose (20%), 3) DDGS (15%), and 4) lactose + DDGS. Diets of interest were fed during phase 1 (d 0 to 14), and a common diet was fed during phase 2 (d 14 to 28). Pigs receiving DDGS in phase 1 had greater ADG (576.2 vs. 534.6 g; P = 0.01) and ADFI (814.9 vs. 751.6 g; P = 0.01) during phase 2 compared with non-DDGS-fed pigs. Pigs receiving lactose during phase 1 had greater ADG (214.7 vs. 177.2 g; P = 0.01) and G:F (741.0 vs. 660.3 g/kg; P = 0.01) and tended to have greater ADFI (289.3 vs. 267.6 g; P = 0.07) during phase 1 but decreased (537.7 vs. 573.1 g; P = 0.09) ADG during phase 2. Serum immunoglobulin analyses and fecal microbial profiling were conducted in both experiments as indicators of health status. No effects of dietary treatment were observed for serum immunoglobulin in either experiment. Fecal microbial profiling resulted in statistically significant effects of dietary treatment with respect to microbial similarity and diversity indices (Exp. 1) and lactic acid-producing bacteria (Exp. 2), where main effects of both lactose and DDGS were observed with respect to putative Lactobacillus reuteri (P < 0.05). Results from Exp. 1 indicate that decreased concentrations of DDGS early in the nursery phase may negatively affect growth performance; however, growth performance may be maintained when inclusion of high concentrations (30%) of DDGS is delayed until the late nursery period. Results from Exp. 2 indicate that lactose may be incorporated in nursery diets containing DDGS to help maintain growth performance, and DDGS and lactose may affect fecal microbial profiles.     

Association of citrus psorosis B symptoms with a sequence variant of the Citrus psorosis virus RNA 2

Citrus psorosis virus (CPsV), the type species of genus Ophiovirus, is the presumed causal agent of a bark scaling disease in citrus plants. CPsV virions are kinked filaments composed of three negative‐strand RNA molecules and a ～48‐kDa coat protein. The virus induces two different syndromes: psorosis A (PsA), characterized by limited bark scaling lesions in the trunk and main limbs, and a more aggressive form of the disease called psorosis B (PsB) with rampant bark lesions affecting even thin branches and chlorotic blotches in old leaves. In the greenhouse, the PsA and PsB syndromes can be induced by graft inoculating healthy citrus seedlings with non‐lesion or with lesion bark inoculum from PsA‐affected field trees. PsA‐ and PsB‐inducing CPsV sub‐isolates obtained by this procedure from the same tree showed identical single‐strand conformation polymorphism (SSCP) profiles in homologous segments of the RNAs 1 and 3, whereas segments of the RNA 2 enabled discrimination between PsA‐ and PsB‐associated sequence variants. SSCP analysis of the RNA 2 population present in different tissues of psorosis‐infected plants showed that: (i) PsA‐inducing isolates contain PsB‐associated sequence variants at low frequency, (ii) the PsB‐associated sequence variant is predominant in blistered twigs and gummy pustules affecting old leaves, characteristic of PsB isolates, and (iii) the PsB‐associated sequence variant accumulates preferentially in bark lesions of the trunk and limbs. SSCP analysis of the RNA 2 population also enabled monitoring of interference between PsA‐ and PsB‐associated variants in plants co‐inoculated with both psorosis types.     

The effects of human trampling on the microbiological properties of soil and vegetation in mediterranean mountain areas

Increased tourist activity and recreational use of wilderness and other protected areas has endangered zones of high environmental value. The aim of this work was to evaluate the effects of trampling intensity (low, high use trails and untrampled trails) and distance from the trails (on the trails, at 10 and 20 m from the trails) on the vegetation, chemical, physical and microbiological properties of a soil in Mediterranean mountain areas. Trail type and distance from the trail significantly influenced several parameters. High use trails showed lower values of plant cover and diversity of vegetation species, as well as soil respiration and some enzyme activities (phosphatase, β‐glucosidase and dehydrogenase) than low use trails. In addition, the effects of trampling spatially extended further from these high use trails than from low use trails. Statistical analysis showed that some microbiological (basal respiration, dehydrogenase activity and β‐glucosidase activity) and vegetal parameters (plant cover and diversity) may be established as a set of indicators for the evaluation of soil quality on these areas subjected to human trampling. We concluded that trampling significantly impacts on soil microbial processes and vegetal communities, and visitor should be restricted from entering ecologically sensitive areas due to the effects of trampling. Copyright © 2010 John Wiley & Sons, Ltd.     

Immunological aspects of Marek's disease in chickens with maternal antibodies]

The dynamics of the production of immunoprecipitation antibodies to Marek's disease virus was studied in the serum of chickens with maternal antibodies in relation to the occurrence of the immunoprecipitation antigens of Marek's disease virus in feather follicles. One-day-old chickens were infected by the contact method with Marek's disease virus. The first occurrence of immunoprecipitation antigen was detected on the 14th day after infection and this occurrence persisted throughout the experiment, i. e. until the 112th day after infection. The antibodies were first detected the 28th day after infection and their titre kept rising until the 98th day after infection. Immunoprecipitation antibodies and antigens of Marek's disease virus were detected in some tumorously changed kidneys. Immunoelectrophoretic examination revealed in the same kidneys immunoglobulins of the class IgY, IgA and beta-globulin. The slowest-migrating fraction of IgY, together with IgA, beta-globulin and C-reactive protein were detected in the skin extracts from infected poultry. Indirect haemagglutination enabled the detection of the presence of haemagglutination antibodies in rabbit immunoglobulin to the skin antigen of Marek's disease virus, and in avian immunoglobulin to the same virus. Haemagglutination antigen was revealed in the extract from tumorously changed kidneys.