Better management practices and their outcomes in shrimp farming: evidence from small-scale shrimp farmers in Southern Vietnam

Despite the growth of aquaculture exports from developing countries to developed countries in recent years, a high percentage of these products are rejected at developed countries’ ports because of non-compliance with international standards. This paper presents a case study of the shrimp aquaculture sector in Vietnam to examine the factors behind the persistence of such port rejections. In particular, we focus on why the so-called better management practices (BMPs) are not appropriately adopted by many farmers and examine whether the number and types of information sources matter in farmers’ decisions on BMP adoption and whether BMP adoption actually leads to better performances. On the basis of our estimation using primary data collected in Southern Vietnam, we find that information sources and training experiences indeed matter in the adoption of a higher number of BMPs and that BMP adoption indeed reduces the possibility of disease outbreaks. These results prove the effectiveness of BMPs and suggest the importance of disseminating knowledge regarding them to farmers through experts.     

Effects of soil type and water saturation on growth,nutrient and mineral content of the perennial forage shrub S<Emphasis Type="Italic">esbania sesban</Emphasis>

Sesbania sesban (L.) Merr is a perennial N₂-fixing tree with high potential for use in agricultural production systems as a green manure and livestock forage. We studied the interactive effects of soil type and water level on the growth, biomass allocation, nutrient and mineral content of S. sesban. Four-week old seedlings of S. sesban were grown for 49 days (n = 5) in a factorial mesocosm set-up with six soil types (sediment, sand, alluvial, acid-sulfate, saline and clay) and three water levels (drained, water-saturated and flooded). The soils tested represent the predominant alluvial soil types of the Mekong delta, Vietnam. Sesbania sesban grew well with relative growth rates (RGR) around 0.08 g g^?1 d^?1 in all studied soil types, except the saline soil where plants died. In the low-pH (3.9) acid sulfate soil, that constitute more than 40 % of the Mekong delta, the RGR of the plants was slightly lower (0.07 g g^?1 d^?1), foliar concentration of calcium was 3–6 times lower, and concentrations of iron and sodium up to five times higher, than in other soils. The nutrient and mineral contents of the plant tissues differed between the soils and were also affected by the flooding levels. Foliar concentrations of nitrogen (50–74 mg N g^?1 dry mass) and phosphorus (5–9 mg P g^?1 dry mass) were, however, generally high and only slightly affected by water level. The results show that S. sesban can grow well and with high growth rates on most wet soils in the Mekong delta, except saline soils where the high salt content prevents establishment and growth. The nutrient and mineral contents of the plants, and hence the nutritional value of the plants as e.g. fodder or compost crops, is high. However, soil type and water level interactively affect growth and tissue composition. Hence, optimal growth conditions for S. sesban differ in the different regions of the Mekong delta.     

Genetic diversity in two threatened species in Vietnam: <Emphasis Type="Italic">Taxus chinensis</Emphasis> and <Emphasis Type="Italic">Taxus wallichiana</Emphasis>

Taxus chinensis and T. wallichiana in have been threatened in their distribution areas in recent decades because of their over-exploitation and reduction and destruction of native habitats. Determining the genetic diversity in populations of the two species will provide guidelines for their protection and preservation. Two hundred and fifteen trees from six populations of T. chinensis and 150 sampled trees of T. wallichiana were sampled. Six microsatellite primer pairs selected from 16 primer pairs were used to investigate genetic variation at the population and species levels. Five yielded polymorphic alleles, and among the 13 putative alleles amplified, 11 were polymorphic (accounting for 76.33 %).Shannon’s information index (I) and percentage of polymorphic bands (PPB) (I = 0.202 and PPB = 67.22 % for T. chinensis; I = 0.217 and PPB = 65.03 % for T. wallichiana). Both species had low levels of genetic diversity (mean H _o = 0.107, H _e = 0.121 for T. chinensis; H _o = 0.095, H _e = 0.109 for T. wallichiana). Genetic differentiation among populations was higher (F _ST = 0.189) for T. chinensis and lower (0.156) for T. wallichiana, indicating limited gene flow (Nm) among populations for T. chinensis (0.68) and T. wallichiana (0.65). Variation among individuals of T. chinensis was 63.59 and 73.12 % for T. wallichiana. Thus, the threatened status of the two conifers is related to a lack of genetic diversity. All populations are isolated in small forest remnants. An ex situ conservation site should be established with a new population for these species that comprises all the genetic groups for the best chance to improve their fitness under environmental stresses.     

Biopore history determines the microbial community composition in subsoil hotspots

Biopores are hotspots of nutrient mobilisation and shortcuts for carbon (C) into subsoils. C processing relies on microbial community composition, which remains unexplored in subsoil biopores. Phospholipid fatty acids (PLFAs; markers for living microbial groups) and amino sugars (microbial necromass markers) were extracted from two subsoil depths (45–75 cm ; 75–105 cm) and three biopore types: (I) drilosphere of Lumbricus terrestris L., (II) 2-year-old root biopores and (III) 1.5-year-old root biopores plus six 6 months of L. terrestris activities. Biopore C contents were at least 2.5 times higher than in bulk soil, causing 26–35 times higher Σ PLFAs g^-1 soil. The highest Σ PLFAs were found in both earthworm biopore types; thus, the highest soil organic matter and nutrient turnover were assumed. Σ PLFAs was 33% lower in root pores than in earthworm pores. The treatment affected the microbial community composition more strongly than soil depth, hinting to similar C quality in biopores: Gram-positives including actinobacteria were more abundant in root pores than in earthworm pores, probably due to lower C bioavailability in the former. Both earthworm pore types featured fresh litter input, promoting growth of Gram-negatives and fungi. Earthworms in root pores shifted the composition of the microbial community heavily and turned root pores into earthworm pores within 6 months. Only recent communities were affected and they reflect a strong heterogeneity of microbial activity and functions in subsoil hotspots, whereas biopore-specific necromass accumulation from different microbial groups was absent.     

Downregulation of Kinesin Spindle Protein Inhibits Proliferation,Induces Apoptosis and Increases Chemosensitivity in Hepatocellular Carcinoma Cells

Background: Kinesin spindle protein (KSP) plays a critical role in mitosis. Inhibition of KSP function leads to cell cycle arrest at mitosis and ultimately to cell death. The aim of this study was to suppress KSP expression by specific small-interfering RNA (siRNA) in Hep3B cells and evaluate its anti-tumor activity. Methods: Three siRNA targeting KSP (KSP-siRNA #1-3) and one mismatched-siRNA (Cont-siRNA) were transfected into cells. Subsequently, KSP mRNA and protein levels, cell proliferation, and apoptosis were examined in both Hep3B cells and THLE-3 cells. In addition, the chemosensitivity of KSP-siRNA-treated Hep3B cells with doxorubicin was also investigated using cell proliferation and clonogenic survival assays. Results: The expression of endogenous KSP at both mRNA and protein levels in Hep3B cells was higher than in THLE-3 cells. In Hep3B cells, KSP-siRNA #2 showed a further downregulation of KSP as compared to KSP-siRNA #1 or KSP-siRNA #3. It also exhibited greater suppression of cell proliferation and induction of apoptosis than KSP-siRNA #1 or KSP-siRNA #3; this could be explained by the significant downregulation of cyclin D1, Bcl-2, and survivin. In contrast, KSP-siRNAs had no or lower effects on KSP expression, cell proliferation and apoptosis in THLE-3 cells. We also noticed that KSP-siRNA transfection could increase chemosensitivity to doxorubicin in Hep3B cells, even at low doses compared to control. Conclusion: Reducing the expression level of KSP, combined with drug treatment, yields promising results for eradicating hepatocellular carcinoma (HCC) cells in vitro. This study opens a new direction for liver cancer treatment. Key Words: Apoptosis, Chemosensitivity, Doxorubicin, Hepatocellular carcinoma (HCC) cells, Kinesin spindle protein (KSP)     

Soil physicochemical properties in a high-quality tea production area of Thai Nguyen province in northern region,Vietnam

This study investigated general physicochemical properties of tea garden soils at the alluvial plain of Cong River in Tan Cuong commune, Vietnam. Four gardens were selected as study sites on three transect lines established perpendicularly to the river. Soil samples were collected from the surface (0–10 cm) and subsurface (20–30 cm). Soil texture classes varied from sandy loam to light clay, which was affected by different terrains along the transect lines as well as severe disturbance such as terracing and earth excavation. The levels of total C and total N were correlated with increasing garden age, suggesting the replenishment of soil organic matter pool by the addition of plant residue and manure. Meanwhile, the soils showed strongly acidic nature with the average pH(H₂O) of 3.7 at the surface and 3.9 at the subsurface. The effective cation exchange capacity (ECEC) was low at 4.7 and 4.9 cmol_c kg^?1, respectively, and dominated by exchangeable Al³⁺. Soil acidification was exacerbated with increasing garden age. However, a relatively large saturation of exchangeable calcium (Ca²⁺), potassium (K⁺), and magnesium (Mg²⁺) on the ECEC was found in the surface soils. The levels of available P were high, occasionally exceeding 1000 and 500 mg kg^?1 at the surface and subsurface, respectively. In spite of strongly acidic condition, ammonium (NH₄-N) applied as fertilizer was converted to nitrate (NO₃-N) to move down to deeper layers. The levels of the bases, P, and mineral N seem to be principally determined by management practices. Significant portion of these nutrients was likely to exist in water soluble forms without adsorption onto soils. It should be required to develop proper schemes and to educate the owners for adequate fertilizer managements.     

Contribution of Fish Production to Farmers’ Subjective Well‐being in Vietnam – A Logistic Model

There is a growing awareness of the importance of food fish production on human nutrition, employment, poverty, and recreation. However, the role of aquaculture in livelihoods of fish farmers has not been considered rigorously. With 120 farmers interviewed in a field survey and a cumulative logistic model, this study identifies some determinants of subjective well‐being of small‐scale fish farmers in Vietnam and examines the role of earnings from fish production in generating their happiness. The results confirm that the farmers receive satisfaction from their farm working. Subjective well‐being of the farmers increases with their job satisfaction and cash earnings from fish farming. A doubling in cash returns from fish culture relative to household income raises a farmer’s happiness probability by an estimated 10.6%. Education also affects farmers’ life satisfaction. For better educated farmers, when their satisfaction from fish culture increases by one level, happiness probability is estimated to increase by 0.23%. Wild fish plays an important role in Vietnamese farmers as a doubling in relative income from wild fish captures raises their estimated probability of happiness by 139%.     

Tropical spiny lobster (Panulirus ornatus) farming in Vietnam – bioeconomics and perceived constraints to development

This paper presents bioeconomic data on lobster farming in Vietnam, and perceived constraints to the development of the industry. The farms were found to be profitable, with an average benefit cost ratio of 1.44 and an average net revenue of 262 million VND year^?1 (or just under US$15 000 year^?1). Investment in the enterprise is high compared with other enterprises in the region. However, disease has the potential to devastate lobster crops and there is little information available to lobster farmers about disease prevention and management. Hence, the lobster enterprise is a high‐risk high‐return industry. The predominant perceived constraints to the development of lobster operations include water quality and temperature issues, insufficient access to credit, good‐quality affordable feed and accurate information about technology improvements in lobster farming. It seems that improving the livelihood of lobster farmers in Vietnam is dependent on reducing their dependence on wild stocks for seed and feed, improving access to credit and improving technical and market information flows. Such improvements are likely to lead to higher profitability, given high export demand and hence sustained high prices for their lobster product.     

Photosynthetic response and nitrogen use efficiency of sugarcane under drought stress conditions with different nitrogen application levels

Drought stress which often occurs during early growth stage is one constraint in sugarcane production. In this study, the response of sugarcane to drought and nitrogen application for physiological and agronomical characteristics was investigated. Two water regimes (well-watered and drought stress from 60 to 120 day after transplanting) and four nitrogen levels (0, 4.4, 8.8 and 13.2 g pot^?1 equivalent to 0, 90, 180 and 270 kg ha^?1, respectively) were assigned in a Split-plot design with three replications. The results showed that photosynthetic responses to light intensity and intercellular CO₂ concentrations of sugarcane were different between fertilized and non-fertilized treatments. Photosynthetic rates of 180 and 270 N treatments, normally, were significantly higher than that of 90 N, but not significant at drought conditions. Photosynthetic rates of 0 N treatment were the lowest under both conditions. Higher nitrogen application supported higher photosynthetic rate, stomatal conductance, and chlorophyll content because of higher nitrogen concentration accumulated into the leaf. Drought significantly reduced the potential photosynthetic rate, stomatal conductance, SPAD, leaf area, and biomass production. Higher nitrogen applications with larger root system could support higher photosynthetic activities to accumulate more dry mass. Strong positive coefficient between photosynthetic and biomass nitrogen use efficiency and drought tolerance index may suggest that higher nitrogen use efficiency could help plants have higher ability to tolerate drought stress.