Vol. 14 No. 8 (2016)

The experiment studied the effect of the expanded clay cultures and slow released fertilizers on growth, development and fresh leaf biomass of Mentha arvensisL. The experiment consisted of two factors: the main factor is 4 expanded clay cultures: G1, G2, G3, G4; Sub-factor is 3 slow released fertilizers: P1, P2, P3. The 12 experimental treatments were arranged in randomized complete block (RCB) and repeated 3 times in the net house of the Faculty of Agronomy, VNUA, in Winter 2014 and Spring 2015. The studied results show that the expanded clay cultures made in Vietnam have porous properties, capacity to store water and nutrients helping plants grow and development better and therefore higher yields compared to the plants grown on the Chinese cultures. The expanded clay culture G1 and slow released fertilizer P1 (NPK ratio is 20:20:15) is the most appropriate substrate for Mentha arvensisL. to grow. Winter crop is suitable for mint basil plant growth, development and obtained higher yields (1.2 to 1.6 times) than spring season.

The objective of the present work was to determine the effect of salicylic acid (SA, 0,25mM and 0.50mM) on growth of cucumber under drought stress imposed by PEG - 6000. Drought markedly reduced growth and development of seedlings, but exogenously applied SA significantly increased plant growth both in drought and non - drought conditions. The increased growth was found for plant height,leaf number, leaf areaandleaf area index, shoot and root dry matter, and chlorophyll aandchlorophyll b content in drought stress applied with 0.25mM SA and 0,50mM SA+ PEG in comparison with those in drought conditions without SA application. In addition, exogenous application of SA lowered the increase inproline contentandMDA, butthe negative effect of drought on H2O2content and Fv/Fm index was notsignificantly ameliorated. Applicaion of0.5 mM SA showed a better effect than 0.25 mM SA.

Five genes Rpp1, Rpp2, Rpp3, Rpp4 & Rpp5 conferringresistancetoPhakopsora pachyrhiziSydow in soybean were identtified. Resistance evaluation of the soybean linescarryingresistant genes shows that genes Rpp2and Rpp4are highlyresistanttosoybean rust in Vietnam while Rpp5ishigh resistanttothe isolatesof rustpathogencollected from Southvietnam. The selection of molecular markers linkedto the above-mentionedresistance genes based on the analysisofcrossing populationsbetween resistant and susceptible cultivars shows that the markers Satt620, Satt288 and Sat_275 are closely linkedto Rpp2, Rpp4and Rpp5with the genetic distance of3.33cM, 2.50cM and4.16cM,respectively. Thesemarkers may beused to identify and select resistancegenes ingermplasm andresistant individuals in segregating populations.

The field experiments were laid out in a randomized complete block design (RCBD) with three replications in 2014 and 2015 summer- autumn cropping season in Yen Thanh and Quy Hop district of Nghe An province to assess the growth and grain yield of fivenewextremely early maturing rice lines (D1, D2, D3, D4,andD5) with twocheck varieties,Khang Dan 18 (KD18)andVat tu- NA2 (NA2). The results showed that the growth duration of therice lines ranged from 88to96 days,shorter than that of the check varieties. Dry matter accumulation rate oftherice lines before heading stage wassignificantly higher than that of the check varietieswhilepest and disease infestationof thelines was lowerat all growth stages.Grain yield accumulation (kg/ha/day) oftherice lines (except D3) wascomparable to orhigher than that of the check varieties. Grain yield oftherice lines was similar to or significantly higher than the check varieties, withD5 showing highest yield in both growing seasons. Amylose content of the rice lines wasbelow 23%, much lower than that of KD18 (above 28%). Cooking quality ofD5 was higher than that of KD18 but similar toNA2.

The phosphorus fertilizer use efficiency in acid sulphate soils usually islow because Fe2+and Al3+ions fix phosphate ions under low pH conditions. The objective of this study was to evaluate the influence of phosphorus fertilizer blended with DCAP on growth and yield of sweet potato, cassavaand yam cultivated in acid sulphate soils in Long My- Hau Giang. The on-farm research was conducted in three farmer’s fields. The treatments included (i) nophosphorus application; (ii) 30 kg P2O5ha-1; (iii)DCAP (2‰) combined with30 kg P2O5ha-1; (iv) 60 kg P2O5ha-1; (v)andDCAP (2‰) combined with60 kg P2O5ha-1. Results showed that application of phosphorus blended with DCAP at 30 kg P2O5ha-1increasedthe diameter, number of tubers and yield on sweet potato and cassava, which were comparable with theapplication of 60 kg P2O5ha-1. Thus, this practiceseemed to be effective inreducing phosphorus fertilizerapplication. However, phosphate fertilizer blended with DCAPdid not increase yam yield.It is needed to further testthe efficiency of phosphate fertilizer blended with DCAP on sweet potatoandcassava cultivated onlarger area in acid sulfate soils in the Mekong Delta.

Salmonella is one of the most common bacteria causing foodborne diseases in human. The objective of this study was to determine the prevalence of Salmonella in pork sold atretail markets in Gia Lam district of Ha Noi andto identify some potential risk factors of Salmonella contamination in pork. The resultsshowed that the prevalence of Salmonella was 34.4%. Wooden table, lack ofmeat inspection, and poor knowledge of sellers about food safety were identified as potential risk factors of Salmonellacontamination in pork. These results could be used as a reference for future interventions to improve the conditions of food hygiene and safetyat the retail markets in Hanoi city.

A study was performed to evaluate the effect of different bottom substrates on survival rate and growth of juvenile sea cucumber (Holothuria scabra) cultured in tanks. Experiment consisted of 4 treatments namely sandy substrate, muddy substrate, sand+mud sustrate mix with 1:1ratio,and brick substrate. Each treatment was repeated three times.Juvenile sea cucumberswithmean initial weight and length of 3.51± 0.14 g and 4.35± 0.51 cm, respectively,were kept in the 250- L tank and provided with slightly continuous aeration at salinity of 30 ppt, and stocking density of30 individuals/m2. After 75 days of culture, survival rate of sea cucumber in sandy, muddy and sand+mud substrates was in the range of 94.4- 100%, and not significantlydifferent(p> 0.05). Particularly, the sea cucumber in the brick treatment experiencedgradual mortalitywith time and complete death at day 62 of culture. The highest specific growth rate and daily growth rate in termsof length and weight of H. scabrain the sandy treatment was observed, and significantly different (p< 0.05) from other substrates. The results suggest that sandy substrate was most suitable while the brick wasnot appropriate for juvenile of sea cucumber H. scabra. Moreover, H. scabracould live and develop on the sand+mud and muddy substrates in tank conditions.

The study was carried out from March to June 2015 at National Broodstock Center for Mariculture Species in Northern Vietnam (Center), Cat Ba, Hai Phong province, to evaluate digestibility of protein (ADP), lipid (ADL) and gross energy (ADE) of some available commercial feeds for pompano,Trachinotus ovatus, using indirect method with chromic oxidize (Cr2O3) 1% as inert marker. Pompano of 400g/fish were held in marine cage- culture system (3 x 3 x 3 m, six of each cage) at density of 10fish/m³. Three commercial aquafeed brands with different protein content,46, 50 and 51% were determined for their digestibility inpompano (abbreviated as D46, D50 and D51) with three replicates. The feaces were collected each day by stripping method before feeding the fish. Fish were fed by hand to apparent satiety, once daily at 9h. Feaces werethen pooled in sealed bottles and stored at- 200C until use. The results showed that ADP of D50 (71.34%) was lowest among experimental diets (P< 0.05), while that of D46 (76.42%) and D51 (77.52%) did not significantly differ (P> 0.05). ADL value of D51 was lower than that of D46 and D50 (P< 0.05). Result of ADE indicated that ability of pompano to digest energy from three commercial diets was similar (P> 0.05). The digestibility of protein and energy of three pellet feedsusedto test in pompano culture wasnot so highandthe quality of these feedsshould be further improved.

The experiment was carried out to evaluate the apparent nutrient digestibility of Guinea fowls at 8 and 10 weeks of age fed diets containing twodifferent protein feed sources and fourcrude protein (CP) levels. The trial used a completely randomized design with two factors and 3 replications. The first factor was two protein feed sources including fish meal and catfish by- product meal and the second factorcomposed offour dietary crude protein (CP) levels of 16, 18, 20 and 22%. The results showed that the apparent EE, NDF and ADF digestibilities of the diet with fish meal were higher than those of catfish by- product meal diet (P< 0.05). The diets contained 20% CP and 18% CP fed Guinea fowls at 8 and 10 weeks of age had the higher DM, OM, EE, CF, NDF, ADF digestibility coefficients and better N retention (P< 0,05).

Rhizobium and Arbuscular mycorrhizal (AM) fungi are capable of symbiosis with plant roots. Theybring many benefits to plant hosts as to stimulatethe growth and development of plants, increase drought tolerance and reduce disease incidence. Thisstudy was executed with the aimto isolate and select Arbuscular mycorrhizae and Rhizobiumstrainswitha high symbiosis for biological material production to revegetationofthe campusscence. Twostrains of Arbuscular mycorrhizal fungi and threeRhizobium strainswere selected thatexhibit fastgrowth, high vitalityand symbiosiswithplantsandcouldbe used for biological material production. The inoculation experiment withbiological materials to therevegetation ofgrass proved the establishment ofthesymbiosisof Rhizobium and Arbuscular mycorrhizal fungi withhost plants thatpromotedthe plant growth and developmentandimproved soil fertility. The vegetation coveringrate using biomaterial treatment wasvery high (95.63%), 1.75 times higher than thecontrol (54.6%) after 5 weeksof application.

A study of Cadmium (Cd) absorption by Solanum nigrumL.(S. nigrum) was conducted through using outdoor pot- culture experiments from March to June 2015. Results showed that S. nigrumbiomass compared with the controlwas not significantlydifferent(P<0.05) under the concentration of 10- 25mg/kg of Cd in soil. The ability to accumulate Cd in the above-ground parts was greater than 100mg/kg dry biomass; TF and BF coefficient was greater than 1. The results of this study demonstrated that S. nigrumis a Cd-hyperaccumulator. This is an important finding that may contribute to solve heavy metal pollution problems as well as to apply phytoremediation in specific situations.

Hanoi city has 30 administrative unitswith area of 3.344,7 km2. High population densityleads to fast development ofinfrastructure and residences,therefore, causing urban “heat island”phenomenonthat dramaticallyaffectsclimate change in Vietnam. Thus, authors usedcharacterized information of bands of satellite image data of Landsat involving 12 urban districts of Hanoi during3 periods,2005,2010,and 2015. With infrared bands, after pixel values wereconverted from digital number (DN) into energy of Atmosphere spectral radiance,the light surface temperaturewas determined. However, the real temperaturewas then determined byadjusting theemissivitty of top cover layer via Normalized Difference Vegetation Index and energy of radiance to top of atmosphere reflectance basedon red and near- infrared bands. Combined with urban land situation estimated from image satellite analysis via accreditation classifyingmethod,the correlation regression equation between surface temperature and urbanization speed was proposed.

Nutrient supply to plants grown on substrate is necessary to obtain high product quality and yield. The objective of the present study was to determine the suitable amount of N, P, K fertilizers for tomato grown on organic substrate. The experiment consisted of 28 pots that were applied with different fertilizer levels. Study results show that pHKCl of organic substrate was neutral (7.28), total nitrogen, phosphorus and potassium were high and equivalent to some popular organic substrates. Different levels of phosphate, potassium fertilizer application (with the same level of nitrogen fertilizer) did not affect tomato yield. Combination of 6.0 g N, 4.5 g P2O5 and 6.0 g K2O per pot improved average fruit weight (78.32 g/fruit) and actual fruit yield (2.38 kg fruit/pot). Potassium fertilizer application significantly affected sugar content of tomatoes (> 5.0%) in pots applied with 4.0 - 6.0 g K2O. After 15 days of fertilization, NO3- content of the tomatoes fluctuated between from 29.7 to 110.3 mg/kg fruit which was lower than VietGap standard.

The objective of the present study was to evaluatethe effectof inoculation of three endophytic bacterial strains on cassavagrowth and yield cultivated on acid sulphate soil in Hau Giang. The endophytic bacterial strains, Burkholderiaacidipaludis, Burkholderia cenocepaciaandBurkholderia pyrrocinia,were isolated from roots and stems of cassava plantscultivated in acid sulphate soilsin theMekong delta. The greenhouse experiment wasconducted at Can Tho University during wet season2014- 2015 and on farmer’sfield in HauGiang in the dry season 2015. The results showed that all threestrains Burkholderia pyrrociniaincreased number of tuber roots, diameter and cassava yield.The combination of 60 kg N ha-1and Burkholderia pyrrociniagave the highest rootyield comparable to90 kg N ha-1ofchemical fertilizer application. The inoculation with endophytic bacteriasave 30 kg N ha-1applied to the cassava.

The shaft of stone sawing machine in working process often occurs faulty. Common form of fault is the wornnessover limited dimension at the center shaft. One of the methods that brings high efficiency andmeeting in time for manufacturing might berestoration of theshaft using build- up welding methodtoachieve the desired dimension. Based on theoreticalresearch onwelding technology, shielded metal arc welding for building- up weldwas selected. This is one of the methods that can be easily usedwith availableequipments. Equipmentselection, welding condition, manufacturing process, manufacturingcondition, andqualityevaluation were done to ensuregood operation after machine assemblage. Different equipmentswere used to test the shaft forroughnessandhardnessand the shaft quality was checked by operation trials. Fivesamples wereselected forrestoration and quality evaluation. Relying on all evaluating methods, all shafts have good quality.

In this study, in vitromass propagationof Coelogyne mooreanaSander ex Rolfe, an endemic orchid (of Vietnam) with its beautiful large,white flowers and fragrance having horticultural potential was accomplished through protocorm formation from shoot tips and subsequent plant regeneration. In the first procedure, shoot tips from in vitrogerminated seedlings were cultured on Murashige and Skoog medium (MS) supplemented with arange of 6- benzylaminopurine (BA) in combination with naphthalene acetic acid (NAA) to determine the best medium for the protocormformation. The results showed that MS medium supplemented with 1.0 mg/l BA and 0.5 mg/l NAA was the most suitable for protocorm formation (6.62 protocorms và formation rate of 86.63%). For subculture, maximum growth of shoots (14 shoots, 2.72 cm height and 3 leaves/shoot) was obtained on MS medium supplemented with0.3 mg/l NAA and 2.0 mg/l BA. The highest frequency of rooting (100%) was observed on ½MS medium supplemented with 20 g/l sucrose, 8 g/l agar, 1 g/l activated charcoal (AC),10% coconut water (CW) and 0.5 mg/l NAA. On this medium, the seedlings reached an average length of 1.66 cm with 3.8 roots per seedling. A successful protocol for micropropagation by shoot tips will contribute to the development of a suitable management program of C. mooreanaSander ex Rolfe.

Gynura procumbens(Lour.) Merr.is a well- known traditional herb in South East Asia and it is widely used to treat inflammation, high cholesterol level, high blood pressure and diabetes. In the present study, the effects of various extractionconditionswere investigated:solvent, solvent concentration, materialto solvent ratio, extraction temperature, extraction time and extraction techniques (maceration and ultrasonic- assisted) on total phenolic content (TPC) and antioxidant activity of the extract fromleaves of Gynura procumbens(Lour) Merr. cultivated in Khánh Hoa province.Folin- Ciocalteu’s method was used for the determination of TPC, while theantioxidant activity was determined by 2,2’ - diphenyl - 1 - picrylhydrazyl (DPPH) radicalscavenging activity and reducing power assays. The best extraction conditions were as follows: 50% aqueous methanolas the extraction solvent,1: 50 materialto solvent ratio, the extraction temperature at60C and the extraction time of30 min, using ultrasonic- assisted extraction. The total phenolic content, DPPH radical scavenging activity (EC50) and reducing power (EC50) under suitable condition, were 48.49 mg GAE/g dry extract, 0.13 and 0.06 mg/ml, respectively. The present study suggested that the Gynura procumbens extract could be a promising source of natural antioxidants.

This study focusedon analyzing factors thataffect customer’s loyalty towards retail services of Hapro Mart supermarket. The study usedprimary datacollected from 197 consumers who usually buy products at Hapro Mart supermarketin Hanoi City. Cronbach’s Alpha wasapplied to test the reliability of the datawhile exploratory factor analysis (EFA) and Structural Equation Modeling (SEM) were used to construct the relationship among factors of service quality, trust, satisfaction and customers’ loyalty. The findingsindicate that service quality had a direct and positive impact on the trust and satisfaction and indirect impactoncustomers’ loyalty. However,commodity components of service qualitydidnot impact on customer’strust and satisfaction. On the other hand, consumer’s loyalty has been positively influencedby 3 factors: trust, satisfaction, and promotion programs and support services. Three solutions weresuggestedto improve customer’s trust and satisfaction and customers’ loyalty:product diversification and differentiation,professional staff training and sale promotion.

Analysing collective action in pig production of Tan Yen collective group showsthat the collective action is characterized by the following: (i) Farmers are volunteer to participate in the collective groupand(ii) Activities of the collective group include coordination in feed purchasing, breed purchasing, veterinary services, access to credit and selling of product. The members of the collective group obtain higher economic return from pig production than non- members. Furthermore, members of the collective group have a better access to market information and technical knowledge than non- members. However, collective action is still weak. Members of the collective group donotparticipate in all collective activities. In addition, the pork label of the collective group lacks standards for traceability. The group leaders are limited in management capacity. The production scale, education level and gender of household head are factors affecting the participation of farmers in the collective group. To promote collective action and to increase farmer’s income, members of the collective group should participate in all collective activities, make plans for pig production scaleamong members, apply VietGap standardsin production,and properly utilize both local cropsas feed and industrial feed. The local authority should support to strengthen thecollective action in order to reduce small scale pig production.

In Thanh Hoa province, there is only a region in Nghi Son Gulf, Tinh Gia district, where farmers have developed pisciculture Marine cage culture. The sea fish farming has increased recently but it has shownevidences ofunsustainable development. The reason could be a high fish density per cage over the efficient level. As a result, the productivity of pisciculture using cages has decreased in recent years. In addition, pisciculturists using cages have faced a number of challenges such as a lack of money capital, a long distance of baby fish, unstable fish feeds,increasedwater pollution, and unstable market. Therefore, this research applied aggregated statiscal method, comparative method and analysis to clarifythe situation and factors affecting the pisciculture using cages in the region, and to propose a set of solutions for development of sea fish farming to exploit the potentials of the region.