Aggregate stability as affected by short and long-term tillage systems and nutrient sources of a hapludox in southern Brazil

The ability of a soil to keep its structure under the erosive action of water is usually high in natural conditions and decreases under frequent and intensive cultivation. The effect of five tillage systems (NT = no-till; CP = chisel plowing and one secondary disking; CT = primary and two secondary distings; CTb = CT with crop residue burning; and CTr = CT with removal of crop residues from the field), combined with five nutrient sources (C = control, no nutrient application; MF = mineral fertilizers according to technical recommendations for each crop; PL = 5 Mg ha-1 y-1 fresh matter of poultry litter; CM = 60 m³ ha-1 y-1 slurry cattle manure; and SM = 40 m³ ha-1 y-1 slurry swine manure) on wet-aggregate stability was determined after nine years (four sampled soil layers) and on five sampling dates in the 10th year (two sampled soil layers) of the experiment. The size distribution of the air-dried aggregates was strongly affected by soil bulk density, and greater values of geometric mean diameter (GMD AD) found in some soil tillage or layer may be partly due to the higher compaction degree. After nine years, the GMD AD on the surface was greater in NT and CP compared to conventional tillage systems (CT, CTb and CTr), due to the higher organic matter content, as well as less soil mobilization. Aggregate stability in water, on the other hand, was affected by the low variation in previous gravimetric moisture of aggregates, which contributed to a high coefficient of variation of this attribute. The geometric mean diameter of water-stable aggregates (GMD WS) was highest in the 0.00-0.05 m layer in the NT system, in the layers 0.05-0.10 and 0.12-0.17 m in the CT, and values were intermediate in CP. The stability index (SI) in the surface layers was greater in treatments where crop residues were kept in the field (NT, CP and CT), which is associated with soil organic matter content. No differences were found in the layer 0.27-0.32 m. The effect of nutrient sources on GMD AD and GMD WS was small and did not affect SI.

Transpiration response of upland rice to water deficit changed by different levels of eucalyptus biochar

The objective of this work was to evaluate the effect of eucalyptus biochar on the transpiration rate of upland rice 'BRSMG Curinga' as an alternative means to decrease the effect of water stress on plant growth and development. Two-pot experiments were carried out using a completely randomized block design, in a split-plot arrangement, with six replicates. Main plots were water stress (WS) and no-water stress (NWS), and the subplots were biochar doses at 0, 6, 12 and 24% in growing medium (sand). Total transpirable soil water (TTSW), the p factor - defined as the average fraction of TTSW which can be depleted from the root zone before water stress limits growth -, and the normalized transpiration rate (NTR) were determined. Biochar addition increased TTSW and the p factor, and reduced NTR. Consequently, biochar addition was able to change the moisture threshold (p factor) of the growing medium, up to 12% maximum concentration, delaying the point where transpiration declines and affects yield.

Serological investigation and PCR in detection of pathogenic leptospires in snakes

Detection of Leptospira by PCR had not yet been described in snakes. This study investigated, by microscopic agglutination test (MAT) and PCR, the presence of antibodies to Leptospira spp. and Leptospira spp., respectively, in venomous and non-venomous wildlife and captivity snakes. All snakes were divided into three groups to be compared: Group 1 (wildlife snakes - WS); Group 2 (snakes in intensive captivity - IC), and Group 3 (collective semi-extensive captivity -CC). Of the 147 snakes studied, 52 (35.4%) were positive for leptospirosis by MAT, 8 (15.4%) belonging to Group 1 (WS), 34 (65.4%) to Group 2 (IC) and 10 (19.2%) to Group 3 (CC). Jararaca (Bothrops jararaca) presented the highest average titer (66.7%, N=22/33) among the three group studied, and Hardjo prajtino was the most prevalent serovar (88.5%, N=46/52), with titers varying from 100 to 3200. Leptospira interrogans was revealed by PCR in kidney and liver of caiçaca (Bothrops moojeni) and jararaca-pintada (Bothrops pauloensis), showing 100% and 93% identity respectively. Future studies should be carried out for better understanding of the role of snakes as a reservoir of Leptospira in nature.

Desenvolvimento, partição de assimilados e produção de matéria seca de plantas de soja (Glycine max (L.) merrill) submetidas a quatro doses de metribuzin

O desenvolvimento, a partição e a produção de matéria seca, foram estudados em soja (Glycine Max (L. ) Merri ll, cv. 'Uberaba'), cultivadas em condições de campo, sob quatro doses de metribuzin - (0,0; 0,35; 0,70 e 1,05 kg i.a. ha-1). O metri buzin não reduziu a população e nem alterou significativamente a razão parte aérea/sistema radicular. A altura média das plantas aumentou significativamente com o incremento das doses de metribuzin, sendo que as alturas máximas das plantas foram 761, 784, 815 e 812 mm, em ordem crescente de dose de metribuzin. As variações das taxas de acúmulo de matéria seca foram nitida mente seqüenciais em todos os tratamentos, ocorrendo mudanças do dreno metabólico preferencial de um órgão para outro, de acordo com as transformações morfológicas das plantas, ressaltando-se que o metribuzin não alterou esse comportamento. Os tratamentos não influencia ramo acumulo de matéria seca das vagens (Wv), no entanto, a partir do inicio da maturação, as plantas-controle apres entaram maiores Wv, provavelmente, devido a maior taxa assi milatória líquida verificada a partir da floração plena. A matéria seca acumulada nos pericarpos (Wp) diminuiu, a partir das sementes completamente desenvolvid os, para todos os tratamentos com exceção de Wp das plantas tratadas com 0,7 kg i.a. ha-1 de metribuzin que, manteve-se estável. Por outro lado, a matéria seca nas sementes (Ws) aumentou de forma acentuada, desde o seu aparecimento até a colheita final , em todas as doses do herbicida.

Frequency of Werner helicase 1367 polymorphism and age-related morbidity in an elderly Brazilian population

Werner syndrome (WS) is a premature aging disease caused by a mutation in the WRN gene. The gene was identified in 1996 and its product acts as a DNA helicase and exonuclease. Some specific WRN polymorphic variants were associated with increased risk for cardiovascular diseases. The identification of genetic polymorphisms as risk factors for complex diseases affecting older people can improve their prevention, diagnosis and prognosis. We investigated WRN codon 1367 polymorphism in 383 residents in a district of the city of São Paulo, who were enrolled in an Elderly Brazilian Longitudinal Study. Their mean age was 79.70 ± 5.32 years, ranging from 67 to 97. This population was composed of 262 females (68.4%) and 121 males (31.6%) of European (89.2%), Japanese (3.3%), Middle Eastern (1.81%), and mixed and/or other origins (5.7%). There are no studies concerning this polymorphism in Brazilian population. These subjects were evaluated clinically every two years. The major health problems and morbidities affecting this cohort were cardiovascular diseases (21.7%), hypertension (83.7%), diabetes (63.3%), obesity (41.23%), dementia (8.0%), depression (20.0%), and neoplasia (10.8%). Their prevalence is similar to some urban elderly Brazilian samples. DNA was isolated from blood cells, amplified by PCR and digested with PmaCI. Allele frequencies were 0.788 for the cysteine and 0.211 for the arginine. Genotype distributions were within that expected for the Hardy-Weinberg equilibrium. Female gender was associated with hypertension and obesity. Logistic regression analysis did not detect significant association between the polymorphism and morbidity. These findings confirm those from Europeans and differ from Japanese population.

Qualidade fisiológica de sementes de soja tratadas com inseticidas sob efeito do armazenamento

Dentre os conceitos modernos de controle de pragas, o uso de inseticidas no tratamento de sementes constitui-se num dos métodos mais eficientes. Deve-se, entretanto, conhecer a influência desses produtos com relação à qualidade fisiológica das sementes tratadas. Objetivou-se através desta pesquisa avaliar a qualidade fisiológica de sementes de soja tratadas com inseticidas, sob quatro períodos de armazenamento (0, 15, 30 e 45 dias após o tratamento). O delineamento experimental foi o inteiramente casualizado, em esquema fatorial 4 x 7, com quatro repetições, onde as sementes do cultivar M-SOY 6101 foram tratadas com os inseticidas thiamethoxam (Cruiser 700 WS), na dose de 250 mL de produto comercial (p.c.)/100 kg de sementes; fipronil (Standak), na dose de 150 mL de p.c./100 kg de sementes; imidacloprid (Gaucho FS), na dose de 150 ml de p.c./100 kg de sementes; [imidacloprid + thiodicarb] (CropStar FS), na dose de 0,3 L. ha-1; carbofuran (Furadan 350 TS), na dose de 1,5 L/100 kg de sementes; acefato (Orthene 750 BR), na dose de 1 kg/ 100 kg de sementes e uma testemunha, sem tratamento. As variáveis analisadas foram: germinação, velocidade de emergência, comprimento de raiz e de plântula e porcentagem de plântulas normais no teste de envelhecimento acelerado. A aplicação dos inseticidas carbofuran e acefato é prejudicial à qualidade fisiológica das sementes de soja cultivar M-SOY 6101, por um período de armazenamento de até 45 dias. A redução da qualidade fisiológica das sementes, condicionada pelos inseticidas avaliados, intensifica-se com o prolongamento do armazenamento das sementes tratadas, recomendando-se, portanto, que o tratamento inseticida das sementes seja realizado próximo ao momento da semeadura.