Canavalia Brasiliensis Research Articles

Xc- System as a Possible Target for ConBr Lectin Interaction in Glioma Cells

Studies have revealed the dependence of glioma cells on iron, making them sensitive to ferroptosis. Ferroptosis can be triggered by inhibition of the xc- system, resulting in redox imbalance and membrane lipid peroxidation. The xc- system is composed of two coupled proteins, xCT and CD98hc. The control of transporters, such as xCT, by the CD98hc glycoprotein suggests that molecules targeting glycans may have an impact on the treatment of glioma. This study evaluated the effect of the Canavalia brasiliensis (ConBr) lectin on C6 glioma cells and compared it with erastin, an xc- system inhibitor. Both induced dose-dependent cell death, accompanied by an increase in the production of reactive oxygen species and a decrease in reduced glutathione. However, co-treatment did not show an additive effect. The analysis was updated by molecular dynamics assessments of the xc- system interacting with ConBr or erastin. The interaction of erastin with the xc- system affects its interaction with ConBr, reducing the antagonistic effect when both are in the protein complex. The data show that ConBr is effective in inducing cell death in glioma cells and regulates the xc system through interaction with CD98hc glycans, showing that lectins have the potential to promote ferroptosis in glioma cells.

Anti-inflammatory and anti-necrotic effects of lectins from Canavalia ensiformis and Canavalia brasiliensis in experimental acute pancreatitis.

Lectins isolated from Canavalia ensiformis (ConA) and Canavalia brasiliensis (ConBr) are promising molecules to prevent cell death. Acute pancreatitis, characterized by acinar cell necrosis and inflammation, presents significant morbidity and mortality. This study has investigated the effects of ConA and ConBr in experimental acute pancreatitis and pancreatic acinar cell death induced by bile acid. Pancreatitis was induced by retrograde pancreatic ductal injection of 3% sodium taurocholate (Na-TC) in male Swiss mice. ConA or ConBr (0.1, 1 or 10mg/kg) were intravenously applied to mice 1h and 12h after induction. After 24h, the severity of pancreatitis was evaluated by serum amylase and lipase, histopathological changes and myeloperoxidase assay. Pancreatic acinar cells were incubated with ConA (200µg/ml) or ConBr (200µg/ml) and taurolithocholic acid 3-sulfate (TLCS; 500µM). Necrosis and changes in mitochondrial membrane potential (ΔѰm) were detected by fluorescence confocal microscopy. Treatment (post-insult) with ConA and ConBr decreased pancreatic damage caused by retrograde injection of Na-TC in mice, reducing pancreatic neutrophil infiltration, edema and necrosis. In addition, ConA and ConBr decreased pancreatic acinar cell necrosis and depolarization of ΔѰm caused by TLCS. The inhibition of necrosis was prevented by the lectin domain blockade. In conclusion, ConA and ConBr markedly inhibited in vitro and in vivo damage, effects partly dependent on the interaction with mannose residues on acinar cells. These data support the potential application of these proteins for treatment of acute pancreatitis.

Chemical composition of cover crops and soil organic matter pools in no‐tillage systems in the Cerrado

AbstractIn no‐tillage systems (NTS), cover crops are recommended to increase the productivity of agricultural systems. Furthermore, a greater diversity of cover crops in NTS favours an increase in soil carbon (C) stocks. However, there are scarce published data on the relationship between the chemical composition of cover crops and the accumulation of labile and stable fractions of SOM. We evaluated the relationship between the chemical composition of cover crops and SOM fractions, C stocks and maize yield. Hemicellulose, cellulose and lignin contents were determined for Urochloa ruziziensis, Canavalia brasiliensis, Cajanus cajan and Sorghum bicolor, cultivated in the off‐season of maize. Canavalia brasiliensis had high N (20.96 g kg−1) and hemicellulose (185.67 g kg−1) contents, lower lignin content (39.50 g kg−1) and high dry matter yield (3,251 kg ha−1). All these characteristics resulted in a better SOM quality. Urochloa ruziziensis, with higher hemicellulose and lower lignin contents, and low lignin/N ratio, was associated with accumulation of TOC (19.95 and 18.33 g kg−1 in 0‐ to 10‐cm and 10‐ to 20‐cm layers, respectively) and mineral‐associated organic C (on average, 16.68 g kg−1) in the soil. Cover plants with N:lignin ratio lower than 2.0 are fundamental for soil C sequestration. In conclusion, it is recommended the adoption of Urochloa ruziziensis and Canavalia brasiliensis as cover plants improve maize production, soil organic matter quality and C sequestration in the Cerrado region.

Nutritional Evaluation of Tropical Forage Grass Alone and Grass-Legume Diets to Reduce in vitro Methane Production

Forage grass nutritional quality directly affects animal feed intake, productivity, and enteric methane (CH4) emissions. This study evaluated the nutritional quality, in vitro enteric CH4 emission potential, and optimization of diets based on two widely grown tropical forage grasses either alone or mixed with legumes. The grasses Urochloa hybrid cv. Cayman (UHC) and U. brizantha cv. Toledo (UBT), which typically have low concentrations of crude protein (CP), were incubated in vitro either alone or mixed with the legumes Canavalia brasiliensis (CB) and Leucaena diversifolia (LD), which have higher CP concentrations. Substitution of 30% of the grass dry matter (DM) with CB or LD did not affect gas production or DM degradability. After 96 h of incubation, accumulated CH4 was 87.3 mg CH4 g−1 DM and 107.7 mg CH4 g−1 DM for the grasses alone (UHC and UBT, respectively), and 100.7 mg CH4 g−1 DM and 113.2 mg CH4 g−1 DM for combined diets (70% grass, 15% CB, and 15% LD). Diets that combined legumes (CB or LC) and grass (UHC or UBT) had higher CP contents, gross, and metabolizable energy (GE, ME, respectively) densities, as well as lower concentrations of neutral detergent fiber (NDF) and acid detergent lignin (ADL). The ME and nutritional variables such as NFD, tannins (T), and CP showed a positive correlation with in vitro net gas production, while ruminal digestibility was affected by CP, ADL, T, and GE. Optimal ratios of components for ruminant diets to reduce rumen net gas production and increase protein content were found with mixtures consisting of 60% grass (either UHC or UBT), 30% CB, and 10% LD. However, this ratio did not result in a decrease in CH4 production.

ConBr lectin modulates MAPKs and Akt pathways and triggers autophagic glioma cell death by a mechanism dependent upon caspase-8 activation

Glioblastoma multiforme is the most aggressive type of glioma, with limited treatment and poor prognosis. Despite some advances over the last decade, validation of novel and selective antiglioma agents remains a challenge in clinical pharmacology. Prior studies have shown that leguminous lectins may exert various biological effects, including antitumor properties. Accordingly, this study aimed to evaluate the mechanisms underlying the antiglioma activity of ConBr, a lectin extracted from the Canavalia brasiliensis seeds. ConBr at lower concentrations inhibited C6 glioma cell migration while higher levels promoted cell death dependent upon carbohydrate recognition domain (CRD) structure. ConBr increased p38MAPK and JNK and decreased ERK1/2 and Akt phosphorylation. Moreover, ConBr inhibited mTORC1 phosphorylation associated with accumulation of autophagic markers, such as acidic vacuoles and LC3 cleavage. Inhibition of early steps of autophagy with 3-methyl-adenine (3-MA) partially protected whereas the later autophagy inhibitor Chloroquine (CQ) had no protective effect upon ConBr cytotoxicity. ConBr also augmented caspase-3 activation without affecting mitochondrial function. Noteworthy, the caspase-8 inhibitor IETF-fmk attenuated ConBr induced autophagy and C6 glioma cell death. Finally, ConBr did not show cytotoxicity against primary astrocytes, suggesting a selective antiglioma activity. In summary, our results indicate that ConBr requires functional CRD lectin domain to exert antiglioma activity, and its cytotoxicity is associated with MAPKs and Akt pathways modulation and autophagy- and caspase-8- dependent cell death.

Pasture diversification affects soil macrofauna and soil biophysical properties in tropical (silvo)pastoral systems

The diversification of tropical pastures with legumes (trees) for increased forage and animal productivity has been advocated. Nevertheless, effects on soil quality and belowground biodiversity, and the implications for sustainable intensification remain poorly documented, particularly when cattle grazing is included in the study. We evaluated the impact of forage system diversification with herbaceous and woody legumes on soil properties and soil macrofauna communities and their spatial heterogeneity in a three-year-old field trial in Cauca Valley, Colombia. Three forage-based systems were compared: (i) a conventional monoculture-species grass pasture system of Brachiaria hybrid cv. Cayman (CP); (ii) a mixed pasture system consisting of Brachiaria grass with the leguminous herb Canavalia brasiliensis (LP); and (iii) a silvopastoral system with rows of the legume tree Leucaena diversifolia planted within LP pastures (SPS). The experiment was arranged in a complete randomized block design with three replicates and grazing cattle rotating across blocks. Plots were grazed by three (treatments CP and LP) or four bulls (SPS) aiming to reflect the expected cattle intensification in SPS systems. Physico-chemical soil properties and macrofauna abundance and their spatial heterogeneity as affected by the distance from the tree rows in SPS, were assessed. Herbaceous legumes positively affected the abundance and diversity of soil macrofauna and soil physical properties in LP and the alleys between tree rows in SPS, as compared to CP. In the SPS, the highest soil quality and macrofauna abundance occurred at the edge of the tree lines, while the highest soil compaction and the lowest abundance of soil macrofauna occurred in the tree rows, probably due to the behavioral change of the grazing cattle in combination with the higher stocking rate in SPS. Soil properties in LP and in the alleys between the tree rows of SPS were comparable despite higher stocking rate in SPS. Overall, the SPS and LP systems, proved to be suitable alternatives to CP allowing for sustainable intensification of pastures although careful evaluation of possible trade-offs associated with increased spatial heterogeneity in SPS is recommended to avoid localized soil compaction. Soil macrofauna, particularly functional groups (classified by feeding habits) proved to be a sensitive soil quality indicator in response to contrasting pasture systems.

PARTICIPATORY EVALUATION OF IMPROVED GRASSES AND FORAGE LEGUMES FOR SMALLHOLDER LIVESTOCK PRODUCTION IN CENTRAL AMERICA

SUMMARYSmallholder livestock systems in Central America are typically based on pastures with traditional grasses and associated management practices, such as pasture burning and extensive grazing. With the rise of the global population and a corresponding increase in demand for meat and milk production, research efforts have focused on the development of improved grasses and the incorporation of legume species that can increase productivity and sustainability of Central American livestock systems. However, farmer adoption remains very limited, in part due to the lack of site-specific evaluation and recommendations by local institutions. Using a multi-site participatory approach, this study examined the potential of five improved grasses and five species of forage legumes as alternatives to the broadly disseminated grass Hyparrhenia rufa (cv. Jaragua) in pasture-based cattle systems in western Honduras and northern El Salvador. Improved grasses (four Brachiaria sp. and Megathyrsus maximus) produced significantly more biomass than H. rufa; also four of the five legume varieties evaluated (Canavalia ensiformis, Canavalia brasiliensis, Vigna unguiculata, and Vigna radiata) demonstrated high adaptability to diverse environmental conditions across sites. Farmer participatory evaluation offers a valuable means to assess performance of forages and will likely contribute to their improved utilization. Future research is needed on more refined management recommendations, pasture system design, costs and environmental benefits associated with the adoption of these forages in local livestock production systems.

In vitro digestion of tropical legume starch is influenced by the combination of heating and soaking treatments

Raw legumes have in general low starch digestion, which limits their use in animal nutrition. This study aimed to determine the effect of different thermal (raw, autoclaving and boiling for 5 and 20 min) and soaking (without or with) treatments on the in vitro degree of hydrolysis (DH) of starch for selected grains of tropical legumes (Canavalia brasiliensis, CB; Lablab purpureus, LP; pink, red and white colour hulls Vigna unguiculata, PVU, RVU and WVU). Indigested residues collected after in vitro sequential pepsin-pancreatin (120–240 min) digestion were used to determine the starch DH and the estimated digestible starch content. The starch content was in general higher when the legumes were treated (e.g. autoclaving increased 28% the starch content of CB). Autoclaving and boiling for 5 min increased the DH for both unsoaked and soaked CB and RVU (+6–16% units), whereas they reduced the DH for unsoaked boiled LP, PVU, WVU and unsoaked autoclaved LP (P < 0.05). Extending the boiling from 5 to 20 min reduced the DH for CB, PVU, RVU and WVU (–8–22% units), whereas it increased 17% units the DH of LP (P < 0.05). In contrast, extending the autoclaving increased DH for soaked LP, PVU and WVU (+4–13% units) (P < 0.05), but did not affect the other legumes (P > 0.05). Similar trends were observed for the estimated digestible starch content, despite the changes in starch content. In conclusion, the effect of soaking and heating treatment combinations on the DH of starch and estimated digestible starch content varied among legumes. Conditions for starch determination may be adapted for legumes.

Efecto de la especie y la edad de rebrote en el perfil de ácidos grasos de leguminosas y arbustivas tropicales

Se evaluó el efecto de tres edades de rebrote (4, 8 y 12 semanas) sobre la producción de forraje, calidad nutricional y perfil de ácidos grasos en leguminosas herbáceas: Clitoria ternatea, Pueraria phaseoloides, Canavalia brasiliensis, Centrosema molle, Centrosema macrocarpum, Alysicarpus vaginalis y Lablab purpureus; en leguminosas arbustivas: Cratylia argentea, Gliricidia sepium, Desmodium velutinum, Cajanus cajan y Leucaena leucocephala; y en una arbustiva no leguminosa: Moringa oleifera (Moringaceae). Se utilizó un diseño de parcelas divididas con bloques al azar, en el cual la parcela principal fue la especie forrajera y la subparcela la edad de rebrote. Los principales ácidos grasos presentes en las especies fueron el ácido palmítico (C16:0), ácido linolénico (C18:3) y linoleico (C18:2). Sin embargo, en las leguminosas herbáceas y arbustivas, el contenido de ácidos grasos fue diferente y disminuyó con la edad de rebrote en los dos grupos. La relación C18:2/C18:3 fue mayor en las leguminosas herbáceas que en las arbustivas, lo cual podría resultar en una mayor concentración de ácido linoleico conjugado (ALC) en la grasa de la leche. La leguminosa Cajanus cajan presentó el mayor (p<0,05) contenido de ácido linolénico (C18:3) y de precursores de ALC en las tres edades de rebrote evaluadas, lo cual sugiere que su uso en la alimentación de bovinos en sistemas de doble propósito resultaría en concentraciones altas de ALC c9 t11 en la grasa de la leche, en comparación con otras especies.

The potent anti-cancer activity of Dioclea lasiocarpa lectin

The lectin DLasiL was isolated from seeds of the Dioclea lasiocarpa collected from the northeast coast of Brazil and characterized for the first time by mass spectrometry, DNA sequencing, inductively coupled plasma-mass spectrometry, electron paramagnetic resonance, and fluorescence spectroscopy. The structure of DLasiL lectin obtained by homology modelling suggested strong conservation of the dinuclear Ca/Mn and sugar-binding sites, and dependence of the solvent accessibility of tryptophan-88 on the oligomerisation state of the protein. DLasiL showed highly potent (low nanomolar) antiproliferative activity against several human carcinoma cell lines including A2780 (ovarian), A549 (lung), MCF-7 (breast) and PC3 (prostate), and was as, or more, potent than the lectins ConBr (Canavalia brasiliensis), ConM (Canavalia maritima) and DSclerL (Dioclea sclerocarpa) against A2780 and PC3 cells. Interestingly, DLasiL lectin caused a G2/M arrest in A2780 cells after 24h exposure, activating caspase 9 and delaying the on-set of apoptosis. Confocal microscopy showed that fluorescently-labelled DLasiL localized around the nuclei of A2780 cells at lectin doses of 0.5–2× IC50 and gave rise to enlarged nuclei and spreading of the cells at high doses. These data reveal the interesting antiproliferative activity of DLasiL lectin, and suggest that further investigations to explore the potential of DLasiL as a new anticancer agent are warranted.

Efecto de especies y manejo de abonos verdes de leguminosas en la producción y calidad de un cultivo forrajero utilizado en sistemas ganaderos del trópico seco

El uso de cultivos forrajeros para corte y acarreo o para ensilar es una alternativa para reducir los efectos negativos de la época seca en la alimentación de animales en sistemas ganaderos doble propósito en el trópico seco. Por otra parte, el uso de abonos verdes de leguminosas es una alternativa al uso de nitrógeno (N) químico para la fertilización en cultivos forrajeros. Con el fin de utilizar las leguminosas como abonos verdes en una forma más eficiente en fincas ganaderas, es necesario seleccionar leguminosas productivas de crecimiento rápidos y adaptadas a sequía y evaluar manejos alternativos de rotación con cultivos forrajeros. En este estudio se evaluaron cuatro leguminosas (Canavalia brasiliensis, Lablab purpureus, Clitoria ternatea y Vigna unguiculata) dos niveles de nitrógeno (0 y 50 kg ha-1), y dos manejos (siembra del cultivo en el primer o en el cuarto mes después de la incorporación del abono) dispuestos en un arreglo de parcelas divididas con tres repeticiones. Las leguminosas con más altos rendimientos (p

Plant lectins ConBr and CFL modulate expression toll-like receptors, pro-inflammatory cytokines and reduce the bacterial burden in macrophages infected with Salmonella enterica serovar Typhimurium

BackgroundPlant lectins have long been used in biomedical research as immunomodulators against tumor cells and microbial infections. PurposeTo test the ability of plant lectins ConBr (Canavalia brasiliensis) and CFL (Cratylia argentea) to activate antimicrobial and immunomodulatory activities of murine peritoneal macrophages (pMØ) infected with a virulent strain of Salmonella enterica serovar Typhimurium (STm). MethodsWe incubated pMØ with non-toxic amounts of ConBr and CFL either before (preventive schedule) or after (curative schedule) exposure to STm. ResultsIn uninfected pMØ, ConBr and CFL greatly increased levels of mRNA transcripts for IL-1β, TNF-α and IL-6 and the inducible nitric oxide synthase (iNOs), but not IL-10 and IL-12. Exposure to naïve splenocytes of culture supernatants of pMØ previously stimulated with CFL resulted in expression of IL-12 and IFN-γ. Both preventive and curative treatment schedules significantly reduced the intracellular load of Salmonella. Experiments in infected macrophages exposed to lectins in the preventive schedule showed that mRNA transcripts for IL-6 and TNF-α were increased by CFL, whereas ConBr enhanced IL-12 (subunit p40). In the curative schedule, CFL induced significant expression of IL-12 (p40) whereas ConBr enhanced expression IL-1β and TNF-α genes. The lectin treatments did not influence on iNOs expression in pMØ infected with STm C5 regardless of the treatment schedule. Curative treatments with CFL increased approximately 130-fold expression of TLR-4 whist expression of TLR-9 was increased by treatments with ConBr. ConclusionWe conclude that lectins ConBr and CFL have immunomodulatory properties that are beneficial on control of cells infected by Salmonella.

Microbial response to the restoration of a Technosol amended with local organic materials

Farmers of western Rwanda directly cultivate tantalite mine soils due to land scarcity with sole reliance on farmyard manure (FYM) as fertilizer. However, there is limited knowledge of its effects on soil microbial properties. We therefore investigated the effects of FYM, Canavalia brasiliensis and Tithonia diversifolia biomass, and Markhamia lutea leaf litter on C and N mineralization and microbial properties in a Technosol (unrestored tantalite mine soil) and an arable soil in a laboratory study. Fresh soils (0–20cm) were amended and incubated for twelve weeks. C mineralization was measured weekly by alkali trap while N mineralization and microbial properties were determined from the incubated soils after 4, 8, and 12 weeks of incubation. The amendments substantially increased (P<0.01) CO2 efflux, N mineralization, and microbial properties compared with non-amended soils. Canavalia and FYM mineralized N while Markhamia and Tithonia immobilized it. Canavalia had the greatest increase in CO2 efflux, net N mineralization, and microbial biomass C and N by 340%, 30–140%, 240–600%, and 240–380%, respectively, compared to non-amended soils after four weeks. Tithonia had the largest increase in ergosterol content by roughly 240% and the greatest contribution of ergosterol to microbial biomass C with marginal effects on microbial biomass C and N. The Technosol had the utmost increases in microbial properties and C and N mineralization, suggesting a greater response to the amendments and seems to have a high potential for quick restoration of soil productivity. The effects of each amendment also suggest optimum benefits through combined use.

Comparison of immunomodulatory properties of mannose-binding lectins from Canavalia brasiliensis and Cratylia argentea in a mice model of Salmonella infection

The immunomodulatory properties of mannose-binding lectins ConBr (Canavalia brasiliensis) and CFL (Cratylia argentea) were investigated comparatively in a model of Salmonella infection. The lectins were intraperitoneally (i.p.) administered to mice daily for three days before the bacterial challenge with Salmonella enterica Ser. Typhimurium (0.2mL i.p.; 107CFU/mL). In vivo assays have shown that both lectins induced a significant leukocyte infiltration into the peritoneal cavity of uninfected mice, which was higher in the CFL group 3days post-infection. Total and differential cell counts in the bloodstreams have shown uninfected animals pretreated with ConBr and CFL exhibited accentuated lymphopenia. Conversely, there was an increasing population of lymphocytes following 3days post-infection in mice pretreated with both lectins. In addition, the bacterial burden was significantly reduced into the peritoneal cavity, bloodstreams, spleen and the liver in these mice. The lectins did not induce the release of pro- or anti-inflammatory cytokines into the peritoneal fluid of uninfected animals. However, following infection, the release of TNF-α and IL-10 in the peritoneal fluid were down-regulated in mice pretreated with both lectins whereas IL-1 was only reduced in mice pretreated with ConBr. Uninfected animals pretreated with CFL exhibited high nitric oxide (NO) content in the peritoneal fluid, which was decreased after infection in comparison to ConBr group. The lectins did not alter the serum levels of NO in uninfected mice but treatments with ConBr significantly reduced the NO content in infected animals in comparison to CFL group 24h after the bacterial challenge. Survival experiments have shown survival rates ranging from 70% to 100% in mice that received CFL or ConBr. On the other hand, untreated mice (PBS group) died 1–6days after infection. We conclude that ConBr and CFL are prospective phytotherapeutics capable of modulate the cascade of pro-inflammatory plus regulatory cytokines and nitric oxide release derived from systemic infections.

Cover Crops and Nitrogen Fertilization Effects on Nitrogen Soil Fractions under Corn Cultivation in a No-Tillage System

The use of cover crops has recently increased and represents an essential practice for the sustainability of no-tillage systems in the Cerrado region. However, there is little information on the effects of nitrogen fertilization and cover crop use on nitrogen soil fractions. This study assessed changes in the N forms in soil cropped to cover crops prior to corn growing. The experiment consisted of a randomized complete block design arranged in split-plots with three replications. Cover crops were tested in the plots, and the N topdressing fertilization was assessed in the subplots. The following cover species were planted in succession to corn for eight years: Urochloa ruziziensis, Canavalia brasiliensis M. ex Benth, Cajanus cajan (L.) Millsp, and Sorghum bicolor (L.) Moench. After corn harvesting, the soil was sampled at depths of 0.00-0.10 and 0.10-0.20 m. The cover crops showed different effects at different soil depths. The soil cultivated with U. ruziziensis showed higher contents of total-N and particulate-N than the soil cultivated with C. cajan. Particulate-N was the most sensitive to changes in the soil management among the fractions of N assessed. The soil under N topdressing showed a lower content of available-N in the 0.10-0.20 m layer, which may be caused by the season in which the sampling was conducted or the greater uptake of the available-N by corn.

Weed suppression by green manure in an agroecological system

ABSTRACT Green manure promotes efficient suppression of weeds, but green manure species can exhibit distinct behaviors, depending on the environmental conditions. This study aimed to evaluate the potential of soil mulching and weed suppression by spring/summer green manure species grown in the spring/summer season, at different growth stages and after management (cut), for 90 days during the cassava crop cycle. The study was carried out in the 2010/2011 season, in a system managed under agroecological principles. The treatments consisted of different green manure species and arrangements: Crotalaria juncea, Cajanus cajan, Canavalia brasiliensis, Canavalia ensiformis, Pennisetum americanum, Crotalaria juncea and Pennisetum americanum intercropped; Mucuna aterrima, Sorghum bicolor, a mixture of all the green manures in study and a control plot under fallow. The experiment was arranged in a randomized block design with four replications. The evaluations of the soil cover either by the green manures or weeds were performed at 45, 90 and 105 days after the emergence of the green manures. The cassava crop was planted under reduced tillage system at 11 days after the cut of the green manures. The percentage of soil covered by weeds and the dry matter produced were evaluated at 30, 60 and 90 days after planting. The results showed that the green manures had a suppressive effect on weeds during their life cycle, as well as during the first months after its management (cut), composing the mulch.

Mealybugs (Hemiptera: Pseudococcidae) species on economically important fruit crops in Sri Lanka

Canavalia brasiliensis has a great potential as green manure in Brazilian Savanna. The species gives nitrogen to subsequent crops and produces excellent dry matter. On the other side, even under suitable environment conditions, several seeds don’t germinate due to the impermeable seed coat. This trial aimed to identify different treatments for dormancy breaking. Some scrub methods were tried: a) manual removal of distal portion of the seed, with or without distilled water soaking; 19 seed immersion on boiling water for 30, 60, 180, 300 and 600 seconds; e) seed immersion on H 2 SO 4 for 5, 10, 15, 20, 30, 40, 50 and 60 minutes; d) thermal impact (24 h at 25 0C followed by 24 h at 5°C or 40°C, then returning to 25°C); e) alcohol immersion for 5, 15, 30 and 60 min.; f) control. Treatments that provided better germination were: removal of distal portion with and without water soaking (99.6 and 99.2% germination, respectively), H 2 SO 4 for 60 min. (95.9%) and boiling water for 60 and 30 sec (97.7 and 94.8% germination, respectively). KEY-WORDS: Green manure; savanna; leguminosae .

The impact of heating and soaking on the in vitro enzymatic hydrolysis of protein varies in different species of tropical legumes

The effects of different thermal (raw, autoclaving or boiling for 5 and 20min) and soaking (with or without) treatments on the degree of hydrolysis (DH) of protein were investigated for selected legumes (Canavalia brasiliensis; Lablab purpureus; pink, red and white colour hulls Vigna unguiculata). Each legume preparation underwent in vitro simulated gastrointestinal tract digestion comprising either pepsin (120min) or pepsin/pancreatin (120/240min) digestion. The DH was determined based on the amount of free amino groups released. Autoclaving for 5min increased the pepsin/pancreatin DH for all the unsoaked and soaked legumes (+20% to 46% units) except Canavalia, while boiling for 5min only increased DH for two soaked legumes (+12% to 28% units). Extending boiling from 5 to 20min increased the DH for three soaked legumes (+5% to 29% units). In conclusion, autoclaving, in general, extensively increased the sequential pepsin/pancreatin DH, while boiling only increased it for selected legumes.

Seed structure in Canavalia brasiliensis Mart. ex Benth. (Leguminosae) and subcellular localization of ConBr lectin: Implications for ConBr biological functions

Lectins are proteins capable of specific and reversible recognition of carbohydrates without modifying them. Many studies have isolated these molecules from Leguminosae seeds but little attention was given to subcellular localization and biological function of these molecules. Therefore, this work aimed to describe Canavalia brasiliensis seed structure and the subcellular localization of ConBr. In addition, we tested the affinity of anti-ConBr antibody for other lectins. To accomplish this, seed fragments were processed for light, scanning and transmission electron microscopy, as well as immunocytochemistry. The anti-ConBr affinity was also tested. Under SEM, the testa showed a regular contour of anticlinal walls without trichomes and inner integument of 10–20 cell layers. The cotyledons presented many parenchymatic cell layers with starch grains and cytoplasmic protein bodies. The immunological identity of anti-ConBr immunoglobulin to ConBr and other lectins was confirmed by immunodiffusion and Western blotting. Ultrastructurally, the cotyledons showed protein bodies characterized by heterogeneous appearance of irregularly formed electron-dense and electron-lucent areas. Immunolocalization showed lectin at both protein bodies and cell wall, however, more studies are required for the elucidation of ConBr functions. Moreover, the affinity of anti-ConBr for different lectins can make this molecule a useful biotechnological tool for lectin studies.

Cover plants and mineral nitrogen: effects on organic matter fractions in an oxisol under no-tillage in the cerrado

Cover plants are essential for the sustainability of no-tillage systems in tropical regions. However, information on the effects of these plants and N fertilization on soil organic matter fractions is still scarce. This study evaluated the effect of cover crops with different chemical composition and of N topdressing on the labile and humified organic matter fractions of an Oxisol of the Cerrado (savanna-like vegetation). The study in a randomized complete block design was arranged in split-plots with three replications. Four cover species were tested in the plots and the presence or absence of N topdressing in the subplot. The following cover species were planted in succession to corn for eight years: Urochloa ruziziensis; Canavalia brasiliensis M. ex Benth; Cajanus cajan (L.) Millsp; and Sorghum bicolor (L.) Moench. In general, the cultivation of U. ruziziensis increased soil C levels, particularly of C in the humic acid and particulate organic C fractions, which are quality indicators of soil organic matter. The C in humic substances and mineral organic C accounted for the highest proportions of total organic C, demonstrating the strong interaction between organic matter, Fe and Al oxides and kaolinite, which are predominant in these weathered soils of the Cerrado.