Cutaneous Basophilia in the Resistance of Goats to Amblyomma cajennense Nymphs after Repeated Infestations

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Resistance of stored bean varieties to Acanthoscelides obtectus (Coleoptera : Bruchidae)

During bean seed storage, yield can be lost due to infestations of Acanthoscelides obtectus Say, the bean weevil. The use of resistant varieties has shown promising results in fighting these insects, reducing infestation levels and eliminating chemical residues from the beans. The expression of resistance to A. obtectus in bean varieties is frequently attributed to the presence of phytohemagglutinins, protease inhibitors and alpha-amylase, and especially to variants of the protein arcelin, which reduce the larval viability of these insects. To evaluate the effect of bean seed storage time on the resistance expression of bean varieties to A. obtectus, tests with seeds of three ages (freshly-harvested, 4-month-old, and 8-month-old) were conducted in the laboratory, using four commercial varieties: Carioca Pitoco, Ipa 6, Porrillo 70, Onix; four improved varieties containing arcelin protein: Are. 1, Arc.2, Arc. 3, Arc.4; and three wild varieties also containing arcelin protein: Arc. IS, Arc.3S, and Arc. 5S. The Arc.5S, Arc. IS, and Arc.2 varieties expressed high antibiosis levels against the weevil; Arc. I and Arc3S expressed the same mechanism, but at lower levels. The occurrence of oviposition non-preference was also observed in Arc.5S and Arc. IS. The Arc.3 and Arc. 4 varieties expressed low feeding non-preference levels against A. obtectus. The expression of resistance in arcelin-bearing, wild or improved varieties was affected during the storage of seeds, and was high under some parameters but low in others. The results showed that addition of chemical resistance factors such as protein arcelin via genetic breeding may be beneficial in improving the performance of bean crops.

The field resistance of potato cultivars to foliar late blight and its relationship with foliage maturity type and skin type in Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Resistance of Santa Ines and crossbred ewes to naturally acquired gastrointestinal nematode infections

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

The Effects of Nectar-Robbing on Fruit Production in Sparattosperma leucanthum (Bignoniaceae)

Many animals behave as robbers or thieves of floral resources, causing damage to floral tissues or consuming resources used to attract pollinators, or producing effects similar to emasculation by reducing the pollen load in the anthers (which generally results in losses in terms of sexual reproduction). The present work examined the direct and indirect impacts caused by nectar-robbing on the reproductive success of Sparattosperma leucanthum. Different manipulations of the flowers were tested to determine if fruit production was influenced by the perforations made in the floral tissues (direct damage), and if there were changes in visitation frequencies or in the behaviors of effective pollinators (indirect damage). Perforations made by nectar robbers did not lower the reproductive success of the plant species studied. The bee Trigona spinipes was the most frequent visitor and caused the largest perforations in the calyx and corolla of S. leucanthum. Additionally, we noted the occurrence of pollen theft by this same bee in flowers that had been protected against nectar-robbing. These results suggest that if S. leucanthum had developed a mechanism of resistance to robbery by T spinipes it would probably have experienced even lower pollination levels as a result of reductions in the quantities of pollen available for transfer by effective pollinators. We were not able to evaluate if nectar depletion through robbery modified the behavior of the effective pollinators (bumblebees of the genus Bombus).

Esterase enzymes involved in pyrethroid and organophosphate resistance in a Brazilian population of Riphicephallus (Boophilus) microplus (Acari, Ixodidae)

Esterases are a group of enzymes that are reportedly associated with acaricide resistance in Riphicephallus (Boophilus) microplus. A comparative analysis was made of the esterase patterns in malathion and deltamethrin-sensitive, tolerant and resistant tick groups, using non-denaturing polyacrylamide gel electrophoresis. Electrophoretical profiles revealed four bands of esterase activity against alpha-naphthyl acetate; which were dubbed EST-1 to EST-4. The EST-3 and EST-4 were detected in all strains and were classified as carboxylesterases (CaEs). The EST-2, classified as an acetylcholinesterase (AChE), was detected in all groups, but its staining intensity increased from susceptible to resistant groups, indicating an altered production according to the degree of resistance. EST-1, which was also classified as an AChE, was detected exclusively in tolerant and resistant groups to both acaricides, but displayed greater activity in the malathion-resistant group. These data suggest that these AChEs may represent an important detoxification strategy developed to overcome the effects of acaricides. (C) 2008 Elsevier B.V. All rights reserved.

Diallel analysis of maize resistance to Phaeosphaeria maydis

Em programas de melhoramento visando resistência genética a doenças, a estimativa de parâmetros genéticos que governam a resistência permite direcionar a introdução de resistência em germoplasmas. O objetivo deste trabalho foi estimar os efeitos heteróticos, a capacidade geral (CGC) e específica (CEC) de combinação, utilizando-se de dois métodos de avaliação da resistência, à Phaeosphaeria maydis através da análise dialélica de 36 híbridos F1 e de suas nove linhagens genitoras, em experimentos conduzidos em três ambientes. Foi utilizado um delineamento experimental em blocos casualizados com três repetições e a parcela experimental foi representada por uma fileira de 5 m. As diferenças entre as estimativas da capacidade de combinação, em diferentes ambientes e para os dois métodos de avaliação, apresentaram efeitos significativos (P < 0.01) para ambientes (E), CGC e CGC x E. O efeito de CEC e a interação CEC x E não foi significativa para os dois métodos de avaliação. Os efeitos de CGC foram mais importantes que CEC nesse conjunto de linhagens, sugerindo que efeitos genéticos aditivos são mais importantes como fonte de variação para resistência a esta doença. Efeitos heteróticos para resistência foram estimados, sendo possível identificar combinações híbridas específicas entre linhagens com alto potencial para o controle genético deste patógeno. Resultados para os dois métodos de avaliação foram praticamente idênticos, embora o método PI seja de maior praticidade de uso.

Modulation of parasitemia and antibody responce to Trypanosoma cruzy by cyclophosphamide in Calomys callosus (Rodentia, Cricetidae)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Combining ability of Phaseolus vulgaris L. for resistance to common bacterial blight

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

MODULATION OF PARASITEMIA AND ANTIBODY-RESPONSE TO TRYPANOSOMA-CRUZI BY CYCLOPHOSPHAMIDE IN CALOMYS-CALLOSUS (RODENTIA, CRICETIDAE)

Calomys callosus a wild rodent, previously described as harboring Trypanosoma cruzi, has a low susceptibility to infection by this protozoan.Experiments were designed to evaluate the contribution of the immune response to the resistance to T. cruzi infection exhibited by C. callosus. Animals were submitted to injections of high (200 mg/kg body weight) and low (20 mg/kg body weight) doses of cyclophosphamide on days -1 or -1 and +5, and inoculated with 4 x 10(3) T. cruzi on day O. Parasitemia, mortality and antibody response as measured by direct agglutination of trypomastigotes were observed. Two hundred mg doses of cyclophosphamide resulted in higher parasitemia and mortality as well as in suppression of the antibody response. A single dose of 20 mg enhanced antibody levels on the 20th day after infection, while an additional dose did not further increase antibody production. Parasitemia levels were not depressed, but rather increased in both these groups as compared to untreated controls. Passive transfer of hyperimmune C. callosus anti-T. cruzi serum to cyclophosphamide immunosuppressed animals resulted in lower parasitemia and mortality rates. These results indicate that the immune response plays an important role in the resistance of C. callosus to T. cruzi.

Acquired resistance of horses to Amblyomma cajennense (Fabricius, 1787) ticks

Acquired immunity of horses to larvae, nymphs and adults of the Amblyomma cajennense tick was evaluated through three consecutive experimental infestations of tick-bite naive hosts. Data from these infestations were compared to those from field-sensitized horses and donkeys. It was observed that tick-bite naive horses developed a low level of resistance after two infestations as shown by a significant decrease in larval yield and a tendency for lower engorged weight of nymphs during third infestation. Ticks fed on field-sensitized horses had a similar biological performance to that observed on the third infestation of tick-bite naive horses but the mean engorged nymph weight was significantly lower than that of the first infestation from tick-bite naive horses. Donkeys presented the strongest resistance with significantly lower engorged weights of all instars and of the egg mass compared to the first infestation of tick-bite naive horses. Donkeys also displayed a significantly higher resistance than field-sensitized horses as demonstrated by significantly lower egg mass weights. Overall these results indicate that donkeys but not horses maintain a strong resistance to A. cajennense ticks. The importance of these findings in relation to vectoring of tick-borne diseases is discussed. (C) 2003 Elsevier B.V. All rights reserved.

Effects of nandrolone decanoate and resistance exercise on skeletal muscle in adult male rats

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Identification and Analyses of Candidate Genes for Rpp4-Mediated Resistance to Asian Soybean Rust in Soybean

Asian soybean rust is a formidable threat to soybean (Glycine max) production in many areas of the world, including the United States. Only five sources of resistance have been identified (Resistance to Phakopsora pachyrhizi1 [Rpp1], Rpp2, Rpp3, Rpp4, and Rpp5). Rpp4 was previously identified in the resistant genotype PI459025B and mapped within 2 centimorgans of Satt288 on soybean chromosome 18 (linkage group G). Using simple sequence repeat markers, we developed a bacterial artificial chromosome contig for the Rpp4 locus in the susceptible cv Williams82 (Wm82). Sequencing within this region identified three Rpp4 candidate disease resistance genes (Rpp4C1-Rpp4C3 [Wm82]) with greatest similarity to the lettuce (Lactuca sativa) RGC2 family of coiled coil-nucleotide binding site-leucine rich repeat disease resistance genes. Constructs containing regions of the Wm82 Rpp4 candidate genes were used for virus-induced gene silencing experiments to silence resistance in PI459025B, confirming that orthologous genes confer resistance. Using primers developed from conserved sequences in the Wm82 Rpp4 candidate genes, we identified five Rpp4 candidate genes (Rpp4C1-Rpp4C5 [PI459025B]) from the resistant genotype. Additional markers developed from the Wm82 Rpp4 bacterial artificial chromosome contig further defined the region containing Rpp4 and eliminated Rpp4C1 (PI459025B) and Rpp4C3 (PI459025B) as candidate genes. Sequencing of reverse transcription-polymerase chain reaction products revealed that Rpp4C4 (PI459025B) was highly expressed in the resistant genotype, while expression of the other candidate genes was nearly undetectable. These data support Rpp4C4 (PI459025B) as the single candidate gene for Rpp4-mediated resistance to Asian soybean rust.

Electrical and optical characteristics of SnO2 thin films prepared by dip coating from aqueous colloidal suspensions

Starting from aqueous colloidal suspensions, undoped and Nb5+ doped SnO2 thin films have been prepared by using the dip-coating sol gel process. X-ray diffraction results show that films are polycrystalline with crystallites of average size1-4nm. Decreasing the thickness of the films and increasing the Nb5+ concentration limits the crystallite size growth during firing. Complex impedance measurements reveal capacitive and resistive effects between adjacent crystallites or grains, characteristic of electrical potential barriers. The transfer of charge throughout these barriers determines the macroscopic electrical resistance of the layer. The analysis of the optical absorption spectra shows that the samples present more than 80% of their transmittance in the visible region and the value of the band gap energy increases with decreasing crystallite size. © 1997 Chapman & Hall.

Standardization of bioassays for monitoring resistance to insecticides in Aedes aegypti

Since the reintroduction of Aedes aegypti in Brazil in the 1980s, insecticide use for its control is routine. The chemical control efficacy is threatened by vectors developing resistance to insecticides. The World Health Organization, recognizing the impact of insecticide resistance in vector control programmes, proposed standardizing bioassays for detecting and monitoring resistance using a diagnostic dose method. As Brazil has a national programme for monitoring the resistance of Ae. aegypti populations to insecticides, this study was designed to compare diagnostic bioassays at WHO suggested concentrations and those estimated for local conditions. Populations were resistant to both temephos doses. But important differences were seen for fenitrothion and malathion, which could lead to under- or over-estimation of resistance respectively. These results and inclusion of a diagnostic dose bioassay standard for larvae are discussed.