Response of photosynthesis and chlorophyll a fluorescence in leaf scald‐infected rice under influence of rhizobacteria and silicon fertilizer

Leaf scald caused by Monographella albescens reduces the photosynthetic area, causing yield losses in rice. This study investigated the efficacy of the rhizobacteria Burkholderia pyrrocinia (BRM‐32113) and Pseudomonas fluorescens (BRM‐32111), combined with silicon (Si) fertilization, to reduce lesion size and the area under the disease progress curve (AUDPC), as well as to minimize the negative effects on gas exchange, chlorophyll a fluorescence, chlorophyll content and the activity of oxidative stress enzymes. The experiment used a completely randomized design with four replications and seven treatments. Compared with plants only fertilized with Si, plants fertilized with Si and treated with BRM‐32113 showed reductions of 22% in scald lesion expansion and 37% in AUDPC, a 27% increase in the rate of CO₂ assimilation (A), a 33% decrease in the internal CO₂ concentration (C_i), and a 40% increase in ascorbate peroxidase activity. It was therefore concluded that the combination of BRM‐32113 with Si fertilization reduces the severity of leaf scald, protecting the photosynthetic apparatus, thus representing a sustainable method of reducing the loss of income caused by leaf scald in rice.     

HEV infection in swine from Eastern Brazilian Amazon: evidence of co-infection by different subtypes

Hepatitis E virus (HEV) is a fecal-orally transmitted member of the genus Hepevirus that causes acute hepatitis in humans and is widely distributed throughout the world. Pigs have been reported as the main source of genotypes 3 and 4 infection to humans in non-endemic areas. To investigate HEV infection in pigs from different regions of Pará state (Eastern Brazilian Amazon), we performed serological and molecular analyses of serum, fecal and liver samples from 151 adult pigs slaughtered between April and October 2010 in slaughterhouses in the metropolitan region of Belém, Pará. Among the animals tested, 8.6% (13/151) were positive for anti-HEV IgG but not for anti-HEV IgM. HEV RNA was detected in 4.8% (22/453) of the samples analyzed and 9.9% (15/151) of the animals had at least one positive sample. Phylogenetic analysis showed that all sequences belonged to genotype 3 that were related to human isolates from other non-endemic regions, suggesting that the isolates had zoonotic potential. Subtypes 3c and 3f were simultaneously detected in some pigs, suggesting co-infection by more than one strain and/or the presence of a recombinant virus. These results constitute the first molecular and serologic evidence of swine HEV circulation in the Eastern Brazilian Amazon.     

Yellow melon yield in response to mineral or organic fertilization

Although current recommendations in Brazil suggest the application of mineral and organic fertilizers, there is little information regarding the interaction between them in melon plants. This study aimed to evaluate the effects of mineral and organic fertilization in the plant development, nutritional status, and fruit yield of yellow melon. The following fertilizations were evaluated: mineral fertilization; bovine manure; bovine manure associated with mineral fertilization; poultry litter; and poultry litter associated with mineral fertilization. Bovine manure and poultry litter were applied at rates equivalent to 15 m³ ha^?1 and 5 m³ ha^?1, respectively. Phosphorus and potassium were applied based on the results of the soil analysis and nitrogen based on the expected yield of 20 to 30 t ha^?1 of fruits. Phosphate and organic fertilizers were applied at the time of preparation of the beds, while nitrogen and potassium were supplied daily through irrigation water. Goldex F1 melon hybrid seedlings were used in the experiment. Plants were collected to evaluate the dry matter production at beginning of flowering, beginning of fruiting, fruit growth, and fruit harvest. Leaves were collected at flowering stage to evaluate the nutritional status of plants. Harvest was made when the fruits reached the intense yellow coloration. Organic fertilizers alone and combined to mineral fertilizer did not affect the dry matter yield of leaves, stems, fruits and shoot, the concentrations of macro and micronutrients in melon leaves, the nitrogen accumulation in the plant, and the yield of the yellow melon. The application of bovine manure associated to mineral fertilization showed the lowest values of nitrogen recovery applied. Bovine manure application resulted in increase of nitrogen organic forms in soil.     

Effect of different concentrations of potassium and magnesium on performance of Litopenaeus vannamei postlarvae reared in low-salinity water and a biofloc system

Effect of K⁺ and Mg²⁺ in water on the performance of Litopenaeus vannamei using bioflocs was evaluated. Control had water with K:Mg (1:4.57) and other treatments (K:Mg of 1:5.4, 1:4.65, and 1:3.77), both with salinity of 4 g/L. Initial mean weight of shrimp was 0.08 ± 0.007 g. No difference in shrimp growth performance and survival was observed (P > 0.05) except in the control. Our results suggest that it is possible to culture postlarvae of Litopenaeus vannamei in low-salinity water with bioflocs when the water has an initial potassium concentration of 30.90 ± 8.5 mg/L and magnesium of 167.0 ± 3.9 mg/L.     

First report of white spot syndrome virus in wild crustaceans and mollusks in the Paraíba River,Brazil

The aim of the present study was to investigate the presence of white spot syndrome virus (WSSV) in the Paraíba River, Brazil. Eight sampling sites were established on the bank of the river near water intake areas for the farming of Litopenaeus vannamei. Ten specimens of the shrimp Palaemon pandaliformis and the gastropods Pomacea lineata and Melanoides tuberculatus were collected at each site. Eighty‐one gill fragments from P. pandaliformis, 40 whole individuals of M. tuberculatus and 26 muscle fragments from P. lineata were collected. All samples were stored in microcentrifuge tubes with 95% ethanol (1:10; v:v). Tests were performed at the Potiporã Molecular Analysis Laboratory (state of Rio Grande do Norte, Brazil) for the detection of WSSV using Loop Mediated Isothermal Amplification with the aid of the LAMP WSSV kit (Concepto Azul, Ecuador). Twenty‐nine per cent of P. pandaliformis, 48% of M. tuberculatus and 8% of P. lineata tested positive. The findings demonstrate that WSSV is present in wild crustaceans and mollusks, which may serve as vectors and/or reservoirs of the virus, thereby posing a potential risk to local shrimp farming. This is the first report of WSSV in wild specimens of M. tuberculatus and P. lineata.