Caracterização fenotípica de rizóbio nativos isolados de solos da Amazônia e eficiência simbiótica em feijão caupi

Biological nitrogen fixation is of fundamental importance for agricultural sustainability, and the evaluation of the rhizobial diversity contributes to the knowledge of their diversity in collections, as well as for later use in agricultural systems. The objective of this paper was to evaluate phenotype diversity and symbiotic efficiency of rhizobia isolates from Amazonian soils when inoculated on cowpea (Vigna unguiculata L. Walp.). The native isolates presented diversity regarding their morphologic and physiological characteristics. It was verified that the inoculation with isolates of native rhizobia contributed to the increase of the biomass, nodulation on cowpea and symbiotic efficiency

Infecção por hemintos gastrintestinais em bovinos de diferentes grupos

As infeções por helmintos gastrintestinais provocam graves prejuízos à pecuária no Brasil. A seleção de animais resistentes a esses parasitas é apontada como sendo uma estratégia que minimizaria os efeitos dessas enfermidades, reduzindo inclusive a freqüência de tratamentos. Para verificar se existe diferença entre raças, durante o período de 14 meses (outubro de 2006 a novembro de 2007) foram observadas 67 fêmeas, sendo 26 da raça Nelore, 23 cruzados ½ Senepol+ ½ Nelore e 18 cruzados ½ Aberdeen Angus + ½ Nelore. Estes animais apresentavam idades entre sete e oito meses, ao início do experimento. Eles foram tratados com medicamento a base de albendazol, 30 dias antes do início do experimento, e permaneceram em piquetes rotacionados de capim-tanzânia, sem qualquer medicação. Mensalmente foram colhidas amostras de fezes para execução de OPG e de coproculturas, e amostras de sangue, para determinação do hematócrito. Os dados de OPG foram transformados em log10(n+1) e submetidos a análise de variância para estudar os efeitos de raça, época do ano e interações. Não houve diferenças significativas entre os grupos genéticos estudados para as médias de OPG e hematócrito. Foi encontrada associação inversa entre os valores de OPG e de hematócrito, sendo que nos períodos mais secos houve decréscimo do OPG e aumento concomitante do hematócrito. As maiores médias de OPG foram verificadas nos meses mais úmidos e quentes e as menores nos mais secos e frios, sendo que variaram entre 3,20 e 0,47, respectivamente. Nos três grupos genéticos pôde ser verificada a distribuição agregada típica das infecções parasitárias. Os principais gêneros encontrados foram Cooperia spp., Haemonchus spp. e Oesophagostomun spp. seguidos de Trichostrongylus spp., em menor proporção. Esses resultados sugerem que bovinos dos grupos genéticos estudados, quando submetidos ao mesmo regime de pastagens, não apresentam diferença significativa quanto à suscetibilidade aos helmintos gastrintestinais

Growth and nutrient contents in lowland rice due to phosphorus and potassium fertilization.

In order to reach an optimum and sustainable production, growers must know the fertilizing potassium (K) and phosphorous (P) application rates. The present study aimed to determine the rice development in response to combined rates of P and K, on Plinthaquults (380-400 g kg-1 of clay), under high and low fertility conditions, in the tropical lowland plain of the Araguaia river, Brazil. Three field experiments were performed, each one consisting of a completely randomized factorial block design, with three replications. Treatments included a combination of six K2O rates (0 kg ha-1, 30 kg ha-1, 60 kg ha-1, 90 kg ha-1, 120 kg ha-1 and 150 kg ha-1) with six P2O5 rates (0 kg ha-1, 30 kg ha-1, 60 kg ha-1, 90 kg ha-1, 120 kg ha-1 and 150 kg ha-1). No interaction effect between P and K rates was observed for the evaluated variables in any fertility level/year. Phosphorous application under low fertility conditions, as well as K under high fertility conditions, affect overall crop nutrition, tillering capacity, yield components and grain yield of lowland rice, though no effects were observed due to the P application in high fertility soils and K in low fertility soils. Under high fertility conditions, the grain yield increment rate due to the K application was 4.04 kg ha-1, whereas in the low fertility areas, such as recently cleared fields, a maximum yield of 7,161 kg ha-1 was achieved by applying 140 kg ha-1 of P

Capacidade de solubilização de fosfatos e eficiência simbiótica de rizóbios isolados de solos da Amazônia

On soils with low available phosphorus, such as the Amazonian upland, the ability of rhizobium strains to solubilize inorganic phosphates is of extreme importance. The objective of this work was to determine the ability of rhizobium isolates from Amazonian soil to solubilize calcium and aluminum phosphate in laboratory, and their symbiotic efficiency to increase N and P contents in cowpea. The rhizobium isolates were evaluated on specific growth media during a period of 15 days, when solubilizing indexes (S.I.) were obtained. From the 205 isolates, 68 solubilized P-Ca and 47 solubilized P-Al, and 32 solubilized P-Ca as well as P-Al. Among the 14 isolates with highest solubilizing activities, eight isolates (INPA R820, INPA R825, INPA R843, INPA R894, INPA R914, INPA R917, INPA R969 and INPA R982) provided higher shoot P and N contents and dry matter

Enzimas hidrolíticas extracelulares de isolados de rizóbia nativos da Amazônia Central, Amazonas, Brasil

Legumes enrich the soil by contributing nitrogen through symbiotic biological nitrogen fixation by rhizobia bacteria. However, very little is known about the extracellular enzymatic profile of these microorganisms. In this context, the production of extracellular hydrolytic enzymes by indigenous strains of rhizobia in Central Amazonia was evaluated. This screening constitutes the first step in selecting indigenous microorganisms that are potentially exploitable as enzyme producers. Indigenous strains of rhizobia were screened for extracellular amylolytic, carboxymethylcellulolytic, lactolytic, lipolytic, pectinolytic and proteolytic activities on modified YMA. Ureolytic activity was detected on a urea-agar slant. Rhizobia strains isolated from cowpea nodules produced more enzymes than those isolated from soybean nodules. Out of all the extracellular hydrolytic enzymes evaluated, only pectinase was not detected in this study. The most frequent rhizobia enzymes were amylase (32.8%), protease (28.4%), urease (20.9%) and carboxymethylcellulase (9.0%). In this study, only amylase and protease enzymes varied significantly among rhizobia strains. INPA strains R-926 and R-915 showed the highest enzymatic levels for amylase (EI = 3.1) and protease (EI = 6.6), respectively. This paper showed some indigenous strains of rhizobia from Central Amazonia as promising sources of industrially relevant enzymes for biotechnological purposes