Foliar application of manganese increases sugarcane resistance to orange rust

Orange rust (Puccinia kuehnii) is a serious disease compromising the sustainability of sugarcane (Saccharum spp.) production. The objective of this research was to study whether supplemental manganese (Mn) supplied through foliar sprays ameliorates negative effects of orange rust on sugarcane and, if so, to reveal the underlying mechanisms. The experiment was conducted using a sugarcane variety susceptible to the disease; a single spray of Mn at 5 g L⁻¹ (Mn_0.5%) or 10 g L⁻¹ (Mn_1%), plus a control (Mn_0%) was performed before pathogen inoculation. Symptom severity, antioxidant metabolism, lignin deposition and anatomical organization were evaluated. Photosynthesis was also measured in newly expanded leaves and plants were harvested to estimate growth responses. The percentage diseased leaf area was reduced from 15% under Mn_0% to 2.2% and 0.9% under Mn_0.5% and Mn_1%, respectively. This decrease was accompanied by increases in biomass production in the plants. Scanning and light microscopy images revealed that Mn treatment caused direct damage to the fungal spores and improved lignin deposition in the mesophyll. In the presence of the disease, Mn-sprayed leaves exhibited lower levels of oxidative stress, in addition to improved structural organization of xylem and phloem vessels compared to the untreated control. The negative effects of orange rust on gas exchange and photochemistry were also ameliorated by Mn application. The results give insight into the mechanisms underlying augmented sugarcane resistance to orange rust under supplementary foliar Mn spray and contribute to the development of sustainable crop production systems by offering alternatives for reduction of disease damage.     

Effect of seasonality and trophic group on energy acquisition in Amazonian fish

Abstract –  The influence of hydrologic cycle and trophic groups on the energy content of food was investigated for five fish species from a Central Amazonian floodplain area. Sampling was carried out monthly using gillnets of different mesh sizes immersed in water for 24 h. We examined the presence and absence of food in fish stomachs and those with food were analysed and their energy content determined. Amongst the trophic groups studied, the piscivores Acestrorhynchus falcirostris and Pygocentrus nattereri showed high numbers of empty stomachs throughout the sampling period and very high levels of energy density in their food, which may explain why they take food less frequently. On the other hand the invertivorous species Hemiodus sp. and Hoplosternum littorale and the herbivore Rhytiodus microlepis , need to take food very frequently. The energy of the piscivorous species' stomach contents was not significantly different during the hydrologic cycle, whereas the invertivore and herbivore varied significantly, showing a general tendency of high levels of energy during high waters.     

Optimization of feeding quantity and frequency to rear the cyprinid fish Garra rufa (Heckel, 1843)

Garra rufa has a high commercial value, but their rearing methods are still unknown. Aspects like an adequate daily dose and feeding frequency need to be investigated. This work aimed to establish the optimal feed dose per day to obtain satiation and the optimal frequency of feeding to rear a specific size class of G. rufa. A total of 60 fish were distributed by six aquaria containing 10 fish. First, the fish were fed twice per day, by providing a feed dose correspondent to 1% of their body weight and increasing 0.1 g/fish on the following days, until finding feed leftovers on the next morning. Afterwards, the fish went through a 1 month experimental trial to evaluate the optimal feeding frequency. Fish growth was compared between feeding the optimal daily dose distributed in two or three feeding moments per day. The optimal dose that ensured satiation was 0.042 g fish^?1 day^?1 (3.2% of fish’ body weight). Feeding the fish three times per day promoted higher growth rates, since the fish’ total length was statistically different between feeding frequencies. Statistically significant differences between feeding frequencies were not observed for growth performance parameters. These results contribute to the aquaculture of this target species, allowing fish industry to more efficiently respond to the high demand for G. rufa and, simultaneously, for its preservation in the wild.     

Effect of environmental factors on the fatty acid profiles and physicochemical composition of oysters (Crassostrea gasar) in Amazon estuarine farming

The objective of this study was to evaluate the effect of environmental factors on the fatty acid profiles and physicochemical composition of Crassostrea gasar cultured in two locations with differences in salinity and precipitation gradients. The study period was divided into four seasonal divisions—the rainy–dry transition period, the dry season, dry–rainy transition and the rainy season. The salinity, pH and temperature were measured at each site during specimen collection. A total of 712 oyster samples were used for fatty acid profiling and physicochemical analysis. Salinity and precipitation were the environmental parameters that influenced the fatty acid profile and physicochemical characteristics of oysters. C. gasar exhibited excellent values of n3 polyunsaturated fatty acids (DHA, EPA and eicosatrienoic), with a predominance of these acids during periods of higher precipitation. Variations in precipitation and salinity resulted in significant differences in oyster nutritional characteristics. Oysters grown in Amazonian estuaries can be considered nutritious throughout the year, with better conditions during the rainy season.     

The use of diatom Skeletonema costatum on aquaculture‐produced purple sea urchin (Paracentrotus lividus) larvae and post‐larvae diet

The quality of the microalgae provided on Paracentrotus lividus larvae rearing is a primordial factor having a direct (nutritional properties) and indirect (water quality) impact on growth, competence and survival. Skeletonema costatum is a diatom commonly used in the bivalve cultivation. However, the use of this diatom in P. lividus larval cultivations is poorly known. The Rhodomonas spp. is a microalgae commonly used in sea urchin larvae culture. Three different diets were tested on P. lividus larvae and post‐larvae cultivation (D1—Rhodomonas marina, D2—S. costatum, D3—mixture of both algae). Larvae fed with the D2 diet (55.8%) and D3 (39.9%) had a survival at 15 DAH higher than D1 (5.5%). The low survival in D1 could be due to the higher microbiological load on microalgae (Vibrio alginolyticus and V. pectenicide). Larvae fed with S. costatum (D2) showed a lower development than other diets. The competency index was lower for larvae fed with the D2. These results show that microalgae diversified diets contribute to a better development of P. lividus larvae. During the settlement and post‐settlement phase, there was also a lower growth of the sea urchin fed with the D2 and a higher survival for D3.     

Quantification of the invasiveness risk of non-native macroalgae in the Azores to support conservation measures

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Regional and sectorial impacts of the COVID-19 pandemic in Sergipe,Brazil

This paper aims at estimating the regional and sectoral impacts of the Covid-19 pandemic in the state of Sergipe, Brazil in 2020. We use an input-output model with partial hypothetical extraction. The main results suggest a significant reduction in economic activity in the state, particularly in the Transport and Industry sectors. On the other hand, the Real estate and Food and Accommodation sectors have a greater capacity for recovery with the introduction of an emergency aid program. The municipalities with the largest absolute impact on gross domestic product are Aracaju, Canindé de São Francisco and Nossa Senhora do Socorro, two of them located in the metropolitan area of Aracaju.     

Control of equine piroplasmosis in Brazil.

The importance of equine piroplasmosis control in endemic countries has increased in recent years and plays an important role to maintain the international market open to the horse industry. The purpose of this study was to demonstrate the occurrence of equine piroplasmosis (Babesia equi or Theileria equi and Babesia caballi) in Brazil--a country where the disease occurs endemically--in different climatic conditions, and to evaluate the results of a strategy for tick control in order to decrease infection rates. Blood samples were taken from 720 horses on 28 farms from different regions and subjected for complement fixation testing. The strategy was based on the control of the tick population by spraying the horses with acaricides, treating positive horses and preventing cattle and horses from grazing together. A significant association was found in the prevalence of antibody titres in tropical and subtropical areas. A significantly lower prevalence rate occurred on those farms where measures to control tick population were established. Farms in endemic countries may significantly reduce the prevalence of equine piroplasmosis by establishing measures to control the tick population and treating chronic carrier horses. Additional measures for controlling ticks in tropical areas are also discussed.     

Variance components and breeding values for growth traits from different statistical models.

Estimates of genetic parameters resulting from various analytical models for birth weight (BWT, n = 4,155), 205-d weight (WWT, n = 3,884), and 365-d weight (YWT, n = 3,476) were compared. Data consisted of records for Line 1 Hereford cattle selected for postweaning growth from 1934 to 1989 at ARS-USDA, Miles City, MT. Twelve models were compared. Model 1 included fixed effects of year, sex, age of dam; covariates for birth day and inbreeding coefficients of animal and of dam; and random animal genetic and residual effects. Model 2 was the same as Model 1 but ignored inbreeding coefficients. Model 3 was the same as Model 1 and included random maternal genetic effects with covariance between direct and maternal genetic effects, and maternal permanent environmental effects. Model 4 was the same as Model 3 but ignored inbreeding. Model 5 was the same as Model 1 but with a random sire effect instead of animal genetic effect. Model 6 was the same as Model 5 but ignored inbreeding. Model 7 was a sire model that considered relationships among males. Model 8 was a sire model, assuming sires to be unrelated, but with dam effects as uncorrelated random effects to account for maternal effects. Model 9 was a sire and dam model but with relationships to account for direct and maternal genetic effects; dams also were included as uncorrelated random effects to account for maternal permanent environmental effects. Model 10 was a sire model with maternal grandsire and dam effects all as uncorrelated random effects. Model 11 was a sire and maternal grandsire model, with dams as uncorrelated random effects but with sires and maternal grandsires assumed to be related using male relationships. Model 12 was the same as Model 11 but with all pedigree relationships from the full animal model for sires and maternal grandsires. Rankings on predictions of breeding values were the same regardless of whether inbreeding coefficients for animal and dam were included in the models. Heritability estimates were similar regardless of whether inbreeding effects were in the model. Models 3 and 9 best fit the data for estimation of variances and covariances for direct, maternal genetic, and permanent environmental effects. Other models resulted in changes in ranking for predicted breeding values and for estimates of direct and maternal heritability. Heritability estimates of direct effects were smallest with sire and sire-maternal grandsire models.     

Response to long‐term selection for egg production in laying hens

1. A White Leghorn line was selected for part‐record hen‐housed number of eggs from 1962 to 1990. Genetic changes were estimated as deviations from its unselected control line.

2. Over the first 10 generations with selection almost exclusively for number of eggs to the age of 273 d, all traits, except rate of mortality, showed significant changes. Regressions per year were: 273 d production, 3.07 eggs; 497 d production, 5.18 eggs; production from 274 to 497 d, 2.43 eggs; age at first egg, ‐2.33 d; mean weight of first 10 eggs, ‐0.82 g; body weight at 497 d, ‐19.02 g and rate of mortality, 0.19%.

3. Over the rest of the period increasing selection pressure for egg weight has been applied. This resulted in positive changes for this trait and no or small negative changes in egg number.

4. In general, heritabilities and genetic correlations did not change over the period of selection. The heritability of the main trait of selection, production to 273 d was 0.19 ± 0.04 and heritabilities of egg size traits about 0.50.

5. The genetic correlation between egg production to 273 d and mean weight of first 10 eggs was estimated as ‐0.37 ± 0.06 but from the observed response a realised genetic correlation of ‐0.97 was calculated.