Biological performance of Crassostrea gigas stocks produced at different hatcheries and cultivated under same environmental conditions

Production protocols as well as the origin of broodstock in hatcheries are the important factors determining the attributes of Crassostrea gigas oyster spat. Spat from diverse hatcheries may have different attributes for commercial activities. We described the biological performance (growth and condition index – CI) of spat stocks produced at different hatcheries (H1, H2, H3 and H4), and simultaneously cultivated in La Cruz lagoon (Mexico). Analysis of pathogens and genetic variability was performed for each stock. Temperature, salinity, chlorophyll a and seston were measured during samplings. Stocks showed similar growth patterns but each one showed a distinctive curve. Temperature was the governing factor on growth but its effect was variable depending on the stock and whether the temperature increases, stays high or decreases. Availability of food was high producing elevated CI. No presence of pathogens was detected and it was not possible to obtain amplicons of the mitochondrial regions. Despite differences in performance among stocks, all of them showed higher values (growth rates, CI, survival) than the standards reported for the Gulf of California. These findings are useful for the production and cultivation of C. gigas, but more studies are needed to understand the influence of hatchery protocols on spat quality.     

Nitrogen Fertilizers and NH3 Volatilization: Effect of Temperature and Soil Moisture

ABSTRACT

The volatilization of ammonia is the main reaction that decreases the efficiency of nitrogen fertilization and in order to reduce losses. new technologies such as addition of N-n-butyltriamide thiophosphate (NBPT) to the conventional urea granule (UNBPT) or the covering with polymer and sulfur (UPS) have been developed with the aim to optimize nitrogen fertilization. This work aimed to evaluate the volatilization of ammonia (NH₃) in conventional urea (CU) and fertilizers with associated technology under: (a) three temperature conditions (b) and three soil moisture management. The fertilizer CU presented the highest losses by volatilization of 25.93 mg dm^?3 while fertilizers with associated technology registered 23.93 mg dm^?3 and 8.26 mg dm^?3 for UNBPT and UPS. respectively. The highest volatilization of NH₃ was registered at 45°C for all fertilizers. Fertilizers with associated technology extended the N-release time. delaying the volatilization peak up to the 6^th day or even promoted the gradual release of fertilizer in the soil. such as UPS. The UNBPT showed the lowest volatilization values in the 1^st water application. while the CU had lower volatilization values at 25°C (14.48 mg dm^?3 NH₃) and 35°C (16.99 mg dm^?3 NH₃) when the matric potential was increased from ?100 to ?50 kPa in the 1^st application of water. The UPS did not differ from the volatilization values for the three times of water application.     

Economic liberalization and external shocks. The hypothesis of convergence revisited for the Mexican states, 1994–2015

We study the convergence hypothesis for Mexican states during the period 1994–2015 considering the impact not only of NAFTA but also of other external shocks, such as China’s entry into the World Trade Organization (WTO) in 2001 and the global financial crisis of 2008. Using econometric panel data models with no fixed effects to avoid small sample bias, the main results indicate: (a) presence of absolute divergence, consistent with a sigma process divergence, particularly in the period after the outbreak of the global crisis of 2008; and (b) a process of weakening conditional convergence across the sub‐periods analyzed.     

Post-emergence application of herbicides and growth regulators on soybean growth and agronomic performance

Journal of Crop Science and Biotechnology - Plant lodging is among the factors that limit the productive potential of the soybean crop. Growth regulators or even herbicides may be used in pre- and...     

Haemorrhagic septicaemia in the hybrid surubim (Pseudoplatystoma corruscans×Pseudoplatystoma fasciatum) caused by Aeromonas hydrophila

Intensive culture of the hybrid surubim (Pseudoplatystoma corruscans × Pseudoplatystoma fasciatum) in Brazil is responsible for the occurrence of diseases and consequent economic losses. However, the causative agents are not well known. The objective of this study was to isolate and to characterize the pathogenic agent responsible for mortalities in cultured surubim and to demonstrate its virulence. Ten fish from a fish farm located in the Mato Grosso do Sul State (Brazil) were collected and 14 haemolytic bacteria characterized as Aeromonas hydrophila were isolated from the kidneys (eight) and brain (six). As an experimental challenge, fish weighing 98.1±23.6 g were injected with 1 mL of saline solution and 2 × 10², 2 × 10⁴, 2 × 10⁶ and 2 × 10⁸ CFU A. hydrophila mL^?1. Fish infected with 2 × 10⁸ CFU showed increased external and internal symptoms and mortality of 50±12.5% after 96 h. Increased A. hydrophila concentration was responsible for a decrease in haematocrit percentage and erythrocyte number, lymphocytes and eosinophils, as well as an increase in monocytes, neutrophils, serum agglutination titre and serum antimicrobial activity. It was concluded that A. hydrophila was responsible for characteristic symptoms of bacterial haemorrhagic septicaemia as well as important haematological and immunological alterations, which led to surubim mortality.     

Effect of probiotic (Bacillus spp.) addition during larvae and postlarvae culture of the white shrimp Litopenaeus vannamei

The effect of the addition of Bacillus probiotic during larvae and postlarvae culture of the white shrimp Litopenaeus vannamei was examined in three separate experiments: (I) Nauplius_4‐5 to Zoea₃, which were exposed to probiotic in the water (P_w), only in the microalgae (P_m), in the water and microalgae (P_wm) and a control with no probiotic (C); (II) Mysis₁ to Mysis₃, which were exposed to probiotic in the water (P_w), only in Artemia (P_a), in the water and Artemia (P_wa) and a control (C); (III) PL₁ to PL₁₀, which were exposed to similar treatments for mysis experiment. The use of probiotic Bacillus spp. resulted in an increase in the survival and growth of zoea and mysis phases, especially when the probiotic was added only in the water. For postlarvae, the use of the probiotic had no influence on the zootechnical parameters, however, there was a reduction in the count of presumptive Vibrio both for water and shrimp.     

Design and validation of a wireless sensor network architecture for precision horticulture applications

This paper proposes a general wireless sensor network architecture for monitoring horticultural crops that are distributed among small plots scattered at distances of up to 10 km from one another. The technology used for the real implementation of the architecture is based on the B-MAC (Berkeley Medium Access Control) medium access protocol to assure a high degree of sensor node power autonomy. To resolve this issue, a series of specialized sensor nodes (Soil-Mote, Environmental-Mote and Water-Mote) have been developed along with a gateway to interconnect them with the farm central offices. Before starting device development, simulations were conducted to ensure that acceptable performance would be achieved with the selected technology in terms of node autonomy, achieved throughput and delays. To that end, it was necessary to implement the selected B-MAC protocol in the ns-2 (Network Simulator-2) simulation framework. The final system was deployed on a real crop to check and validate the simulation results against experimental results.     

Selection of snap bean recombined inbred lines by using EGT and SSD

With the objective of selecting superior recombinant lines of snap bean, four segregating F₂ populations were selected by early generation testing and advanced by single seed descent. In a randomized complete block design with two replications within sets 120 F_6:7 lines were obtained and evaluated for seven traits of agronomic interest. The mean pod yield of the F_6:7 generation was 72% higher than in generation F₂, confirming the efficiency of early selection. There was genetic variability in the F_6:7 lines within the sets. The selection of superior genotypes was possible by the high estimates of narrow-sense heritability. Highest gains in simultaneous selection of traits were expressed by the indices proposed by Mulamba & Mock for the genetic standard deviation and by Williams, based on tentatively attributed arbitrary weights. Line 3 of the F_6:7 generation, with a yield of 8,050.0000 kg ha⁻¹ and pod fiber content of 0.3650% is highly promising to be release as new cultivar.     

Impacts of thinning on structure,growth and risk of crown fire in a Pinus sylvestris L. plantation in northern Spain

We studied the combined effects of thinning on stand structure, growth, and fire risk for a Scots pine thinning trial in northern Spain 4 years following treatment. The thinning treatments were: no thinning, heavy thinning (32–46% of basal area removed) and very heavy thinning (51–57% of basal area removed). Thinning was achieved via a combination of systematic and selective methods by removing every seventh row of trees and then by cutting suppressed and subdominant trees in the remaining rows (i.e., thinning from below). Four years after thinning, mean values and probability density distributions of stand structural indices showed that the heavier the thinning, the stronger the tendency towards random tree spatial positions. Height and diameter differentiation were initially low for these plantations and decreased after the 4-year period in both control and thinned plots. Mark variograms indicated low spatial autocorrelation in tree diameters at short distances. Diameter increment was significantly correlated with the inter-tree competition indices, and also with the mean directional stand structural index. Two mixed models were proposed for estimating diameter increment using a spatial index based on basal area of larger trees (BALMOD) in one model versus spatial competition index by Bella in the other model. As well, a model to estimate canopy bulk density (CBD) was developed, as this variable is important for fire risk assessment. Both heavy and very heavy thinning resulted in a decrease of crown fire risk over no thinning, because of the reduction in CBD. However, thinning had no effect on the height to crown base and thus on the flame length for torching. Overall, although thinning did not increase size differentiation between trees in the short term, the increase in diameter increment following thinning and the reduction of crown fire risks support the use of thinning. Also, thinning is a necessary first step towards converting Scots pine plantations to more natural mixed broadleaved woodlands. In particular, the very heavy thinning treatment could be considered a first step towards conversion of overstocked stands.