Economic viability of retrofiting emitters in center pivot irrigation systems

Although several studies have been conducted to evaluate the uniformity of water application under center pivot irrigation systems, there are few studies concerning the economic perspective of such coefficient. The aim of this study is to present a methodology to accomplish an economic analysis as support for the decision-making to retrofit emitters in center pivot irrigation systems, and to attribute an economic meaning to the uniformity coefficient of water application taking into account the response function productivity to the amount of water applied and the sale price of the crops. In the hypothetic calculation example considering the variation of revenue of potato crop under center pivot irrigation system, it was verified that the area with uniformity coefficient of water application of 90% brought an income increase of BR$ 1,992.00, considering an area about 1,0 ha. Thus, it can be concluded that the methodology presented has met the objectives proposed in the study and made it possible to attribute an economical meaning to the coefficient of water uniformity application.

Genetic diversity among proso millet (Panicum miliaceum) biotypes assessed by AFLP technique

The Amplified Fragment Length Polymorphism (AFLP) technique was used to access genetic diversity between three domestic and nine wild proso millet biotypes from the United States and Canada. Eight primer combinations detected 39 polymorphic DNA fragments, with the genetic distance estimates among biotypes ranging from 0.02 to 0.04. Colorado-Weld County black seeded and Wyoming-Platte County were the most distinct biotypes according to the dissimilarity level. A UPGMA cluster analysis revealed two distinct groups of proso millet without any geographic association. Six weed biotypes exhibiting some characters of cultivated plants were grouped together with domesticated biotypes of proso millet while the three typical wild phenotypes were clearly clustered into another group according to AFLP markers.

Globaalin kirkon tulevaisuus

Kirjallisuusarvostelu

Prospección de las combinaciones de herbicidas para prevenir malezas tolerantes y resistentes al glifosato

El intenso empleo de glifosato contribuyó a la difusión de malezas con tolerancia a este herbicida, incluyendo especies como Ipomoea nil, bejuco en Argentina, o corriola, o corda-de-viola en Brasil. A su vez, el uso intensivo de imadozolinonas en ciertas regiones de Argentina contribuyó a la aparición de biotipos resistentes a herbicidas que actúan inhibiendo la enzima ALS como Amaranthus quitensis, yuyo colorado o ataco, conocido como carurú en Brasil. En ese país, también, aumentó la difusión de malezas con resistencia a glifosato como en Euphorbia heterophylla, leiteiro o amendoim-bravo y en Lolium multiflorum, azevém. El objetivo de esta investigación fue evaluar el antagonismo o el sinergismo de todas las combinaciones posibles entre dos de los siguientes herbicidas: glifosato, imazetapir, clomazone y lactofen, en el control de las malezas mencionadas. Biotipos susceptibles para todos herbicidas fueran usados en la investigación. Plántulas de yuyo colorado juveniles con dos cm de altura y de las otras malezas mencionadas con siete cm, fueron tratadas con los siguientes herbicidas en g ha-1 i.a.: glifosato 108; imazetapir 10; clomazone 160 y lactofen 30, aplicados solos. Otros seis tratamientos fueron incluidos en todas las combinaciones posibles entre dos de los herbicidas y dosis mencionados. También se empleó un testigo sin tratar. El efecto de la combinación de los herbicidas dependió de la especie evaluada y también de los herbicidas utilizados. Se obtuvo sinergismo solamente para la mezcla glifosato más imazetapir en ataco. Clomazone fue el herbicida con más antagonismo, y lactofen tuvo efecto neutro en la mayoría de las mezclas. Las combinaciones son consideradas potencialmente útiles en el control de malezas tolerantes o resistentes a glifosato.

Critical period for weed control in potatoes in the Huambo Province (Angola)

The effects of different weed management periods on potatoes were studied in three areas (Bailundo, Chianga and Calenga) of the central highlands of Angola and in three cropping seasons, from June 2005 to May 2007. Six weed-management treatments were used to identify critical periods of competition and to allow the development of more precise management recommendations. Total potato yield ranged from about 22 t ha-1 in weed-free plots to about 3 t ha-1 with no weed control a yield loss of 86%. Major weed species Galinsoga parviflora, Cyperus esculentus, Bidens biternata, Amaranthus hybridus, Nicandra physaloides, Portulaca oleracea and Datura stramonium differed from area to area. The species G. parviflora dominated the weed flora in all three areas 73, 97 and 72 plants m² 50 days after crop emergence in Bailundo, Chianga and Calenga respectively, in dry season trials; while C. esculentus was also present in Chianga and Calenga, with an average density of ca 30 plants m-2 in dry season trials. Gompertz and logistic equations were fitted to data representing increasing periods of weed-free growth and weed interference, respectively. Critical periods for weed control, with a 95% weed-free total yield, were estimated from 26 to 66 and from 20 to 61 days after emergence for the rainy and dry seasons, respectively. Weed competition before or after these critical periods had negligible effects on crop yield.

Respuestas morfológicas y anatómicas de Tessaria absinthioides (Hook. et Arn.) DC. a la salinidad

T. absinthioides, Inuleae, Compositae, is a weedy species that is spreading in the irrigation area of the Colorado River, Argentina. This species can be found in normal and saline soils. Morphological and anatomical variables were measured with two salts, sodium chloride and sodium sulfate, with three levels of osmotic potential -0.4, -0.8 and -1.5 MPa, in hydroponic culture, using Hoagland solution as the cultivation media. The total diameter of the roots of plants growing in Na2SO4 and NaCl increased when the osmotic potential was -0.4 MPa. In plants growing in NaCl this may have resulted from the increase in the size of the cortical cells and in plants growing in Na2SO4, the diameter increased may be due to an increase in the cambial activity. The number and length of shoot internodes decreased with increasing salinity, even though this was not statistically significant. In comparison to the control, the total diameter of the shoot increased at -0.4 MPa and decreased with the reduction of the osmotic potential. In comparison to the control, the length of the leaves decreased at -0.4 MPa and the leaves width increased at the same concentration. The palisade parenchyma appeared less developed in saline conditions. In comparison to the control, the number of hairs increased at -0.4 MPa. T. absinthioides acts as a semihalophytic species, according to the salt ranks it tolerates. The mechanisms of adaptation to saline conditions are succulence in root and stunted growth if the salt in the media is NaCl, and the production of haloxeromorphic characters if the salt in the media is Na2 SO4

Studies on ATP-diphosphohydrolase nucleotide-binding sites by intrinsic fluorescence

Potato apyrase, a soluble ATP-diphosphohydrolase, was purified to homogeneity from several clonal varieties of Solanum tuberosum. Depending on the source of the enzyme, differences in kinetic and physicochemical properties have been described, which cannot be explained by the amino acid residues present in the active site. In order to understand the different kinetic behavior of the Pimpernel (ATPase/ADPase = 10) and Desirée (ATPase/ADPase = 1) isoenzymes, the nucleotide-binding site of these apyrases was explored using the intrinsic fluorescence of tryptophan. The intrinsic fluorescence of the two apyrases was slightly different. The maximum emission wavelengths of the Desirée and Pimpernel enzymes were 336 and 340 nm, respectively, suggesting small differences in the microenvironment of Trp residues. The Pimpernel enzyme emitted more fluorescence than the Desirée apyrase at the same concentration although both enzymes have the same number of Trp residues. The binding of the nonhydrolyzable substrate analogs decreased the fluorescence emission of both apyrases, indicating the presence of conformational changes in the neighborhood of Trp residues. Experiments with quenchers of different polarities, such as acrylamide, Cs+ and I- indicated the existence of differences in the nucleotide-binding site, as further shown by quenching experiments in the presence of nonhydrolyzable substrate analogs. Differences in the nucleotide-binding site may explain, at least in part, the kinetic differences of the Pimpernel and Desirée isoapyrases.

Mycoflora and aflatoxigenic species in derivatives of milled rice

Thirty samples of rough rice stored for 6, 12 and 24 months in government authorized warehouses of the state of Rio Grande do Sul, Brazil, were simultaneously collected. After milling of the product, 90 samples (30 of polished rice, 30 of rice bran and 30 of rice hull) were evaluated for their mycoflora, aflatoxigenic species and aflatoxin contamination. The following fungi, listed in decreasing order of frequency, were isolated on Potato-Dextrose Agar: Aspergillus spp., Nigrospora spp., Penicillium spp.; Fusarium spp.; Mucor spp.; Cladosporium spp.; Trichosporon spp. and non-sporulated fungi. The degree of fungal contamination (colony forming units per gram of product) was lowest in polished rice, increasing progressively in samples of rice bran and rice hull. Among the Aspergillus species, A. flavus and A. candidus were isolated most frequently. Of the A. flavus isolates, 52.6% strains were found to be toxigenic and produced only Group B aflatoxins. Analysis of the 90 samples did not reveal the presence of aflatoxins in the rice derivatives.

Effect of enzymatic hydrolysis on some physicochemical properties of root and tuber granular starches

Enzymatic hydrolysis of granular starch is an important tool to provide information about granule structure. Cassava, sweet potato, Peruvian carrot, and potato starches were hydrolyzed by bacterial α-amylase at 37 °C for 48 hours, and the physicochemical properties of the residues from hydrolysis were determined. Cassava starch was the most susceptible to enzyme displaying 20.9% of hydrolysis, whereas potato starch was the most resistant with 5.9%. The granule average size varied from 10.8 to 23.4 μm for Peruvian carrot and potato starches, respectively. With the use of SEM, a smooth granule surface was observed for all native starches. Cassava and sweet potato starches displayed an A-type X-ray diffraction pattern, while Peruvian carrot and potato starches showed a B-type pattern. After hydrolysis, cassava, sweet potato, and Peruvian carrot starches showed some well degraded granules, whereas potato starch presented a slight sign of degradation. The amylose content of the starches decreased with hydrolysis for cassava, sweet potato, and Peruvian carrot starches and was kept unchanged for the potato starch. As expected, intrinsic viscosity and pasting properties decreased for all hydrolyzed starches. There is no difference between thermal properties of native and hydrolyzed starches. These results suggested that hydrolysis occurred in amorphous and crystalline areas of the granules. The B type diffraction pattern in conjunction with the big granule size of the potato starch may have contributed to the greatest resistance of this starch to hydrolysis.

Sugarcane starch: quantitative determination and characterization

Starch is found in sugarcane as a storage polysaccharide. Starch concentrations vary widely depending on the country, variety, developmental stage, and growth conditions. The purpose of this study was to determine the starch content in different varieties of sugarcane, between May and November 2007, and some characteristics of sugarcane starch such as structure and granules size; gelatinization temperature; starch solution filterability; and susceptibility to glucoamylase, pullulanase, and commercial bacterial and fungal α-amylase enzymes. Susceptibility to debranching amylolytic isoamylase enzyme from Flavobacterium sp. was also tested. Sugarcane starch had spherical shape with a diameter of 1-3 µm. Sugarcane starch formed complexes with iodine, which showed greater absorption in the range of 540 to 620 nm. Sugarcane starch showed higher susceptibility to glucoamylase compared to that of waxy maize, cassava, and potato starch. Sugarcane starch also showed susceptibility to debranching amylolytic pullulanases similar to that of waxy rice starch. It also showed susceptibility to α-amylase from Bacillus subtilis, Bacillus licheniformis, and Aspergillus oryzae similar to that of the other tested starches producing glucose, maltose, maltotriose, maltotetraose, maltopentose and limit α- dextrin.

Optimization of extrusion process for production of nutritious pellets

A blend of 50% Potato Starch (PS), 35% Quality Protein Maize (QPM), and 15% Soybean Meal (SM) were used in the preparation of expanded pellets utilizing a laboratory extruder with a 1.5 × 20.0 × 100.0 mm die-nozzle. The independent variables analyzed were Barrel Temperature (BT) (75-140 °C) and Feed Moisture (FM) (16-30%). The effect of extrusion variables was investigated in terms of Expansion Index (EI), apparent density (ApD), Penetration Force (PF) and Specific Mechanical Energy (SME), viscosity profiles, DSC, crystallinity by X-ray diffraction, and Scanning Electronic Microscopy (SEM). The PF decreased from 30 to 4 kgf with the increase of both independent variables (BT and FM). SME was affected only by FM, and decreased with the increase in this variable. The optimal region showed that the maximum EI was found for BT in the range of 123-140 °C and 27-31% for FM, respectively. The extruded pellets obtained from the optimal processing region were probably not completely degraded, as shown in the structural characterization. Acceptable expanded pellets could be produced using a blend of PS, QPM, and SM by extrusion cooking.

6-n-propyltiouracil (PROP) taster status in Brazilian adults

The objective of this study was to determine PROP (6-n-propyltiouracil) taster status in adults and its relationship with anthropometric variables and pleasantness of sugar, salt, and fat. A total of 123 subjects rated the intensity of PROP and sodium cloride (NaCl) solutions using the labeled magnitude scale. For pleasantness evaluation, it was used concentrated orange juice (sugar) and mashed potato (salt and fat). The subjects were classified as non-tasters (n = 35), medium-tasters (n = 33) and super-tasters (n = 55). In this study, no relationship was found between PROP taster status and age, sex, weight, body mass index, and pleasantness. Although genetic markers may influence the degree of liking of certain foods, one must consider that the mechanisms influencing eating behavior in humans are complex, and that psychological, social, and economic factors play a key role in response to food.

Thermal inactivation of polyphenoloxidase and peroxidase in Jubileu clingstone peach and yeast isolated from its spoiled puree

The thermal inactivation of yeast isolated from spoiled Jubileu peach puree and that of polyphenoloxidase (PPO) and peroxidase (POD) in cv. Jubileu, which is widely cultivated in southern Rio Grande do Sul state, Brazil, were studied. PPO and POD were extracted using the protein powder method and submitted to partial purification by precipitation followed by dialysis. The enzymatic activity was determined measuring the increase in absorbance at 420 nm for PPO and 470 nm for POD. The yeast used in this investigation was isolated from spoiled Jubileu peach puree at 22 °Brix, with total initial microbial count of 22 × 10² UFCmL- 1. Stock cultures were maintained on potato dextrose agar (PDA) slants at 4 °C and pH 5 for later use for microbial growth. In all cases, kinetic analysis of the results suggests that the thermal inactivation was well described by a first-order kinetic model, and the temperature dependence was significantly represented by the Arrhenius law. Both enzymes were affected by heat denaturation, and PPO was more thermostable. PPO was also more thermosTable than the yeast isolated from peach puree. The D60-values were 1.53 and 1.87 min for PPO and yeast isolated from spoiled Jubileu peach puree, respectively.

Detection, transmission and pathogenicity of fungi on Blepharocalyx salicifolius (H.B.K.) Berg. seeds

The objective of this study was to identify the fungi associated with the fruit and seeds of Blepharocalyx salicifolius and verify their transmission and pathogenicity to seeds and seedlings. Fungal identification on seeds was made using the blotter test and potato-dextrose-agar but only the blotter test was used for fruit. Fungal transmission to seedlings was evaluated using four replications of 50 seeds planted in vermiculite. The pathogenicity of the fungi, Colletotrichum sp., Curvularia sp., Cladosporium sp. Pestalotia sp. and Macrophomina sp. was tested. Potentially pathogenic and saprophytic fungi were found on the fruits and seeds. The transmission of Cladosporium sp. from seeds to seedlings was verified, and Cladosporium sp. Pestalotia sp. and Macrophomina sp. were found to be pathogenic to B. salicifolius seedlings.