This study aimed to find out the correlation between spawning numbers of black tiger shrimp and quality of their postlarvae. The study was conducted with pond reared and wild caught shrimp broodstocks of 190?210 g each. The broodstocks were reared individually in 200-L tank with recirculating water. After eye stalk ablation, shrimp spawned several times, and their larvae were reared for evaluation of quality. The results of study showed that growth of larvae and postlarvae reduced through diffent spawning numbers. The first three times of spawning after eye stalk ablation, broodstocks produced good larvae which had best growth. Those spawned after molting produced larvae with poorest growth. Larvae and postlarvae from different spawning of wild-caught shrimps performed better growth of body length than those of the pond-reared broodstocks. The survival rates of PL15, for both wild caught and farmed broodstocks were high through different spawning numbers after eye stalk ablation. Survival rate of PL15 from wild caught broodstocks were higher than those of the pond-reared ones though was not significantly different (p>0.05). The quality of PL15 of both wild caught and pond-reared broodstocks in the first three times of spawning after eye stalk ablation were highest, and it reduced from the forth spawning, especially spawnings after molting.

The study was performed on two different materials: in vitro seedlings and in vivo sections of shoots with sprouting axillary buds. The purpose was to study on the interfering of concentration of colchicine and immersed time in these materials to get tetraploid cells. The results of colchicine application in vitro seedlings concluded that 3cm was the minimum length of in vitro seedlings to be applied colchicine, and the 100% mortality was all concentrations of colchicines at 24 hours. The highest survival rate of seedlings was on two treatments of 0.05% colchicine and 0.1% colchicine for 3 hours. In colchicines application in vivo sections of shoots with sprouting axillary buds, the results indicated that highest survival rate of scions after colchicine treatment or after grafting 20 days were on two treatments of 0.1% colchicine, 24 hours and 0.2% colchicine, 48 hours. Lastly, the lethal dose for 100% of sections was at colchicine concentration of 0.2% for 72 hours.

This study was carried out in potassium (K) deficiency risk areas in intensive triple rice soils to determine (i) different K fractions in soil, (ii) response of rice to K fertilizer and indegious soil K supply. Soil K fractions were analyzed on 10 sites in Cai Lay - Tien Giang and 10 sites in Cao Lanh - Dong Thap. Response of rice to K fertilizer and capacity of K supplying of soil were determined from K omission plot with K fertilizer application but optimum levels of Nitrogen (N) and Phosphorous (P) fertilizers were applied. The results showed that exchangeable K (0.63 - 2.71 mmol/kg) and nonexchangeable K (1.60 - 5.94 mmol/kg) was evaluated at low to medium-low ranking, but total K content was ranged at rich level. These results meant that although K potential in soil is high, available and slowly available K in soil is low; therefore it may result in K deficiency in rice. The result of response of rice to K fertilizer study showed that there was a significant yield increase in K fertilizer treatment compared to no K fertilizer treatment; however indegious K supply from soil was about the same in both with and without K fertilizer treatmenst. Because available K in soils was at low level, it is recommended that K fertilizer should be applied to maintain high yield and high soil   K supply.

Alpha-cypermethrin is one of active ingredients which was formed in many different trade names of pesticides permitted for use in Vietnam. It is also one of the pesticides commonly used in rice cultivation in the Mekong River Delta. Effects of alpha-cypermethrin on enzyme cholinesterase and growth fingerling climbing perch (Anabas testudineus) was carried out in laboratory. The results showed that alpha-cypermethrin was highly toxic to perch, with a 96h-LC50 of 10.49μg/L. After 36 hours explored to alpha-cypermethrin concentrations (0.105, 1.049 and 2.623g/L), ChE was inhibited 5.3%; 36.1%; 39.8% of control, respectively. ChE recovered quickly when water was changed. Alpha-cypermethrin did not cause significantly reduction of specific growth rate, non-significantly increase feed conversion ratio. This study indicated that using alpha-cypermethrin for rice as indicated dose is likely to cause direct mortality for the perch. Monitoring fate of alpha-cypermethrin on soil and water in rice-field after spraying and effects of this insecticide on Anabas testudineus is highly recommended.

The objective of this study is to assess and predict groundwater resources in Tra Vinh province using MODFLOW software. Firstly, the groundwater resources system in the study area is devided into 7 layers. Input data included recharge, evaporation and exploitation data ; boundary conditions (rivers) and observation well distribution. The model was calibrated for the time of 720 days (24-time steps). The results show that groundwater resources for exploitation in Pleistocen aquifer is about 9,974 m3/day. This information is very useful for suitable groundwater exploitation in the study area. The prediction results reveal that the water level and drawdown are -9.5m and 3.9m, respectively. This result provides useful information for better understandings of the dynamics of groundwater resources in the aquifers which can be used as a base for establishing the groundwater observation network in the future.

This study was conducted to aim at reducing post-harvest decay, controling the development of many physiological disorders and extending the shelf-life of Duong mandarin. This experiment include 7 treatments (control, dipping with 4, 6, 8% CaCl2 solutionand 4,6,8% Ca(NO3)2 solution), random complete design. Fruits were stored in  the laboratory of Plant Science, Agriculture and Applied Biology department, Can Tho University. Results recorded as follows: dipping fruits with 8% CaCl2 solution effects delayed ripening process, without affecting the quality (TSS, pH, ascorbic acid), extend skin colour of fruit the longer blue, reduced fruit weight loss, limiting diseases and prolonged their storage life up 20 days in laboratory conditions (30-32 0C, 68 - 70% RH).

The objective of this study was to determine the effect of alternate wetting and drying (AWD) compared to continous flooding (CF) irrigation on nitrogen mineralization and potential nitrification (nitrate and nitrite) from paddy soil. The research has been conducted under two water management regimes in alluvial rice soil in Cuu Long Rice Research Institute during dry season 2010. Rate of NH4+-N has been determined by 15N  technique. Contents of soil NH4+-N and NO3- + NOư2--N increased by applying alternate wetting and drying (AWD) and the rate of NO3- + NOư2--N mineralized reached highest at 65 days after sowing (DAS), while NO3--N in continuously flooded (CF) soil almost disappeared at 15 DAS. Implementation of AWD irrigation may considered as one of important factors accelerated N mineralization in Mekong delta rice soils.

Aquatic plants are the subject of many researches with different goals such as environmental indicators, environmental changes, pollution treatments, and nutrient uptake. In order to contribute to applied research on bioindicators in water management the study "The distribution of aquatic plants in the organic polluted canals in Can Tho City in rainy season" was carried out. Three canals were selected in this study, including Kenh Lo 91, Cai Son ?Hang Bang and Kenh Hem 51. The results revealed that in all canals surveyed, chemical oxygen demand concentration ranged from 32.07 mgl-1to 138.47 mgl-1, total nitrogen constituted between 3.89 mgl-1 and 33.79 mgl-1, and total phosphorus ranged from 2.86 mgl-1 to 11.14 mgl-1. This study mainly observed on aquatic macrophyte and common twenty species were found under14 families of plants. Particularly, nine species occured in all three canals. Five dominant aquatic plants were determined Eichhornia crassipes, Hymenachne acutigluma, Brachiaria mutica, Colocasia esculenta L. and Ipomoea aquatica with important index 75%, 55%, 48%, 46% and 34% respectively.

This study was caried out to determine the optimal concentration of paclobutrazol (PBZ) and Potassium chlorate (KClO3) as foliar spraying on the flowering of fourteen-year-old mangosteen trees in Cau Ke district - Tra Vinh province, 2010/2011 season. The factorial experiment with two factors was arranged in randomized completely design, three replications, each replication had a tree. Two factors were PBZ concentrations (0; 500 and 1,000 ppm) and KClO3 concentrations (0; 1,000 and 2,000 ppm). Paclobutrazol and KClO3 were sprayed when the leaves were 2.0-month-old. The results showed that: spraying with PBZ at 1,000 ppm resulted in flowering ratio and yield/tree higher than that at 0 and 500 ppm. Spraying with KClO3 at 2,000 ppm resulted in flowering ratio and yield/tree higher than at 0 and 1.000 ppm. The results also showed interacting of PBZ and KClO3 did not effected on flowering ratio and yield/tree, combinatorial interactions of PBZ at 1,000 ppm and KClO3 1,000 or 2,000 ppm spraying had flowering ratio and yield/tree higher than those of other combinatorial interactions. However, there was not significant different between PBZ and KClO3 concentrations as well as combinatorial interaction about quality of fruit.

Three field experiments were conducted to evaluate effect of biofertilizer on yield  of vegetable (fruit-eating vegetable) such as streaked egg-plant (Solanum melongena), okras (Abelmoschus esculentus), pungent pepper (Capsicum fruitescens L.) cultivated on alluvial soil of O Mon district - Can Tho city from April to October, 2010. The result of experiment showed that using liquid biofertilizer composing of some strains Azospirillum lipoferum and Burkholderia vietnamiensis (nitrogen-fixing bacteria), Pseudomonas stutzeri (phosphate-solubilizing bacteria) and Bacillus subtilis (potassium-solubilizing bacteria) saved up from 25% chemical fertilizer for okras (30 kg N, 15 kg P2O5, 25 kg K2O/ha) and pungent pepper (50 kg N, 37.5 kg P2O5, 37.5 kg K2O/ha) to 50% chemical fertilizer for streaked egg-plant (50 kg N, 40 kg P2O5, 80 kg K2O/ha), however, yield did not differ using 100% chemical fertilizer treatment. Concurrently, quality fruit of biofertilizer treatment to via nitrate content in fruit was lower than 100% chemical fertilizer treatment.

Evaluating 34 rice varieties of Oryza sativa L., in which two standard resistant varieties (PTB33 and OM4495) and one infected variety (TN1), obtained from Biotechnology Research and Development Institute, University of Can Tho and Mekong Delta Rice Institute resistance to brown planthopper (Nilaparvata lugens Stal) using molecular marker RG457, RM190 and standard seedling box test method of IRRI (1996). By using molecular marker RM190, there were 25 resistant varieties and nine infected varieties to brown planthopper with the band size of about 130bp and 120 bp, respectively. By using RG457 marker, there were five varieties showing resistant heterozygous genotype with the band size of about 200, 250, 350 and 600 bp, nine varieties carrying homozygous resistance with band size of about 200, 250 and 350 bp and 20 varieties carrying infected homozygous genotype with the band size of about 200 and 600 bp. In the 34 rice varieties, 13 varieties including OM4495 carrying two planthopper resistance genes of bph4 (Bph3) and Bph10 linked with two molecular markers RG457 and RM190, two varieties PTB33 and OM2395 carried only Bph10 resistance gene linked with RG457, 12 varieties carried bph4 (Bph3) gene linked with molecular marker RM190 and seven varieties including standard planthopper infected variety TN1 without carrying planthopper resistance gene above. Testing planthopper resistance of 34 rice varieties by standard seedling box test method of IRRI (1996), most of rice varieties carry planthopper resistant genes tested with two molecular marker RG457 and RM190 were serious planthopper infections of scale 7 to 9. Rice varieties OM6377, OM4103 and AS996 carrying resistance genes bph4 (Bph3) and Bph10 were slightly infected and resistant with brown planthopper from levels 3 - 5. 

Soil morphology and soil structure play very important roles to soil fertility. The research was conducted to determine the soil morphological characteristics, the structural development and to identify the factors which are affecting to the formation and development of soil structure on major alluvial soil group in the Mekong Delta, Vietnam. Two master soil horizons (A and B horizon) of five typical soil types of major alluvial soil group were selected for study. With 100 soil samples, 50 households were collected and interviewed. Soil pits were dug for detailed morphological description based on the guidelines of FAO, 2006. The results showed that soil profile is usually differentiated into 04 master soil horizons, by the order of ApBg1Bg2Cg(Cr) within 200 cm soil depth. Surface soil horizons of fluvial soils deposited with fluvial materials and varied in the thickness of 20-25cm, coloured by fresh brown or reddish brown; soil structural development essentially occurs in A and B soil horizon, moderately developed at the upper Bg horizon (15-50cm), prismatic shape compounded by angular blocky structure (50-100 mm and 10-20 mm), dominant dark brown soil mottles occuring at the depth of 15-50cm in the soil profile. Whereas, alluvial soils having a thin surface horizon (10-15cm), dark gray or brown soil matrix colour; abundant black decomposed organic matter in the soil matrix, massive or weak soil structural development in the top soil. Moderate and strong soil structural development can also be found in the B mastrer soil horizon, angular blocky structure (20-50 mm, 50-10 mm and 10-20 mm) at the depth of 10-80 cm from topsoil. Soil structures are originated by the physical soil repening process. Mono-rice cultivation, long reduction period, soil tilled under wet condition by heavy tractors those deteriorated the soil structure. So, alternative cash crop with rice cultivation, organic fertilizer and soil preparation at suitable soil moisture are the necessary activities need to be done for soil structure improvement and development in the Mekong delta.

Subject to survey the prevalence of Salmonella on waterfowl (ducks, Muscovy, goose) in Hau Giang province and determine the presence of two strains of Salmonella enteritidis and Salmonella typhimurium (linked to food poisoning in humans) in waterfowl products (meat, eggs) carried out from March to November 2011. Results by 298 samples (58 samples of meat, 102 egg samples, 138 samples) have determined the prevalence of Salmonella spp. on waterfowl is 19.13%; In particular, the prevalence of duck is 17.43; Muscovy and goose is 25 and 23.44%. Prevalence by type of sample (carcass, feces, egg shells, yolk) respectively 32.76%, 21.01%, 13.73%, 0.13. Just found salmonella enteritidis in meat samples (3.45%) and fecal samples (0.72%), found no presence of Salmonella typhimurium in this study.

Water pollution caused by waste water from fish processing factories is a current concern of public community. The presence of phosphorous in treated water is considered as one of the main causes of nutrient accumulation process leading to eutrophication in surrounding river systems. In order to find solutions for removing phosphorous from waste water, phosphorous removal capacity of a material from natural basalt was evaluated. In fact, 1g basalt soil adsorbed 1.51 mg PO43-. The results indicated that basalt soil was potentially effective in treating wastewater from fish processing factories with 99.7 % of phosphate was removed and the remaining concentration of total phosphorus in the effluent water was about 0.31 mg/L

This study aims to assess impacts of different meteo-hydrological factors (including: Temperature, sunshine, rainfall, and water level) on rice yield in the An Giang province by analyzing the trends and correlations between the measured factors and actual rice yield. Apart from such the meteo-hydrological factors, the impacts of different agricultural practices factors (including: Seed, fertilizer, and insect) on the rice yield are also analyzed. The results showed that there is a trend of increase in low-temperature and rainfall, and another trend of decline in high-temperature and sunshine. In addition, there is a low correlation between temperature, sunshine and minimum water level with rice yield (the lowest value of correlation in Dong-Xuan season is 0.03% and in He-Thu season is 3.2%). However, the correlations between rice yield and insect and rainfall are relatively high (the greatest values are 44.6 and 79.2%, respectively). Therefore, the attention to the variations of rainfall (especially in the context of future climate change) should be taken into account for further research as such the variations give great impacts on rice yield, and thus livelihood of local residents of the Vietnamese Mekong Delta.

Effects of different salinities from 5-30? on the growth and survival rate of oyster Crassostrea sp were investigated. Oysters were collected from mangrove forest, Ngoc Hien district, Ca Mau province with shell length varied from 55 to 60mm and shell weight from18 to 20g. Oysters were fed with diet consisting of Chaetoceros algae, dried algae and yeast. After 120 days of cultured period, shell length growth rate of oysters were not significantly different among treatments (p>0.05). However, weight gain of oyster in 5? treatment were lower than other treatments (p

Genetic diversity of 32 mangosteen accessions (Garcinia mangostana L.) collected from Binh Dương was examined using Inter Simple Sequence Repeat (ISSR) marker with 11 primers. The results showed 87 PCR amplified DNA products, including 40 polymorphic (45.98%) and 47 monomorphic products (54.02%). Among 11 primers tested, 10 ones gave polymorphic results in which ISSRED-14 primer showed high polymorphism results; this could be useful for genetic diversity study of mangosteen in the same geographic region. Analyzing by NTSYSpc 2.11a software with UPGMA method showed homology in these mangosteen accessions based ISSR marker varied from 0,75-1,00. Based on cluster analysis, these mangosteen samples could be divided into two large groups. The first group was genetic similarity about 75-89%. The second group with similar levels from 90,3 to 100% could be divided into four sub-clusters. The results suggested that the genetic diversity of 32 mangosteen accessions from Binh Duong was high although mangosteen belongs to opomictic plant. The genetic variation may be due to the accumulation of natural mutations to adapt to living environments.

Reducing greenhouse gas emission has been the trend of many counties and strategy of Ministry of Agriculture and Rural Development (MARD) of Viet Nam, therefore, the Vietnam Low Carbon Rice Project (VLCRP) has implemented in An Giang province aiming to reach triple win: more food, higher income and reducing environmental impacts. Four experimental models of 100ha were conducted in designing randomly with three replications; collecting data on growth of rice plant and sampling gas on the field were done weekly. Results from data analysis showed that the model of alternative wetting and drying irrigation and use of leaf color chart for applying nitrogen fertilizer reached higher yield (0.6-0.9 t/ha), higher in come (8-13 mil. VND/ha) and reduced CH4 emission (19-31%) comparing to the control model. The above mentioned initiative results can recognize that the VLCRP has been a new model with large experimented scope and pioneering project for adaptation and reduction to climate change, this model should be supported by the MARD and locals to expand in rice regions of Viet Nam.

Sixteen nitrogen fixing bacterial strains were isolated from paddy rhizosphere of four regions including Lai Vung, Thanh Binh, Tam Nong and Thap Muoi of Dong Thap province (each districts isolated four bacterial strains). These materials were used to extract DNA and then amplify 16S rDNA region by the primer pair of 27F and 1495R. The PCR products were then digested by four restriction enzymes consisting of MspI, SmaI, EcoRI and HinfI. The restriction enzyme which produced the highest polymorphism was MspI with PIC index of 0.9238, and the lowest polymorphism was EcoRI with PIC value of 0.6104. HinfI and SmaI produced 0.8298 and 0.7471 in PIC value, respectively. Clustering analysis using NTSYS PC2.0 showed that 16 bacterial strains were divided into six groups with dissimilarity of 0.65%. Bacterial strains isolated from the same districts also performed different pattern of DNA bands, and separated into distinct groups in the pedigree diagram. Four bacterial strains isolated from Lai Vung district provided dissimilarity of 1.87%, while the other four strains of Thanh Binh district gave 0.38% in dissimilarity percent. The dissimilarity of bacterial strains within groups of Tam Nong and Thap Muoi district were 1.70% and 1.21%, respectively. Eight bacterial strains isolated from aluminum soil of Tam Nong and Thap Muoi districts were separated into four groups, while the eight other bacterial strains from alluvial soil (Thanh Binh and Lai Vung districts) divided into three distinct groups.

The study was performed on surveys of fruit quality changes at different harvesting stages (90-95, 95-100, 100-105 and 105-110 days after flowering) and stored at 30°C. The results showed that there was different in physical, chemical and sensory characteristics of harvested rambutan at different maturities. Harvested rambutan at 105ữ110 days (after flowering) having a low respiratory rate, high quality, sensory organoleptic and high acceptability of consumers compared to other harvesting stages. Colour chart of rambutan at different harvesting stages was established with the quality criteria. The change of physical and chemical characteristics and commercial value of fruit during storage were also analyzed. According to different harvesting stages, fruit at 105-100 days (after flowering) also showed better attributes associated with eating quality than the others after 4 days of storage. Changes in fruit quality was not reflected during storage.

The study was conducted to determine paclobutrazol (PBZ) dose and the most appropriate period for thiourea spray to induce off-season flowering on ?An Phuoc? wax apple (Syzygium samarangense (Blume) Merr. and Perry). Experiments were carried out at a four years old orchard of ?An Phuoc? wax apple locating in Binh Minh district, Vinh Long province from July 2010 to February 2011. A factorial experiment was arranged in randomized complete block design, with four replications, each of which is equal to one tree. The first factor was PBZ dose (0, 0.75; 1.00; 1.25 g a.i./m canopy diameter), and the second one was 0.5% thiourea spray period (20, 30, and 40 days) after PBZ application (APA) to induce flowering. Results reflected that the treatment of PBZ collar drenching at 0.75 g a.i./m canopy diameter and inducing flowering after wards by thiourea at 40 days APA brought about sooner flowering. The treatment also broght about the highest ratio of  flowering branch/tree (79.17%), higher number of flower bunch (19 bunches/branch). As a result, yield was increased (127 kg/tree), but fruit quality was not negatively influenced.

The objective of the present study was to select sugarcane salt tolerant lines through in vitro mutagenesis. Callus formation was attained from young leaf segments cultured in MS medium supplemented with 3 mg per litre of 2,4-dichloro phenoxyacetic acid (2,4-D) and 0,5 mg per litre of kinetin. Irradiated and non-irradiated calli were screened in vitro through shoot regeneration at 10.0 and 15? of NaCl. Regeneration capacity of irradiated  calluses decreased at 20 to 40 of gamma rays of 60Co and  at 10.0 and 15? of NaCl. The regeneration frequency in irradiated calli was 1.0% to15% as compared to 58,3% in control calli.

In Viet Nam, plants of Nymphaeaceae are mainly wild type which can be used as vegetable. Some plants of Nymphaeaceae were collected and imported to use as the ornamental plants besides wild type. To preserve and use efficiently of plants of Nymphaeaceae, it is necessary to describe and classify them. For these purposes, the study on ?Collection and classification about plants of nymphaeaceae in the Mekong Delta? was carried out to classify collected plants of Nymphaeaceae which were collected in different ecological areas. Their basic and special characteristics are helpful to recognize them. They can be classified into 10 species and 6 unknown species. Basing on the morphologic characteristics and other analyses, there are 29 water lily varieties were classified. Among them, there are 6 deep pink flower water lily varieties, 11 white flower water lily varieties, 2 yellow flower water lily varieties, 3 pink flower water lily varieties, 6 violet flower water lily varieties and one salmon flower water lily variety. The results also showed that 18 water lily varieties with their flowers are very beautiful so they can be used as the ornamental plants. The remain water lily varieties can be used as vegetable or other purposes.

Chalkiness rice is one of the basic standard for rice breeders. It is effected not only in rice quality but also in customers. However, nowadays, nobody published about the genetic characteristic of chalkiness rice. Therefore, this study was carried out to determine where chalkiness rice appear in the panicles, how about the different among panicles per hill, and among hills. This experiment was carried out with randomized design in transplanting a plant per hill in MTL250 rice varieties, and used the same farming technique in West Season 2010. The results showed that there was different about the proportion of chalkiness among three grain places in each panicle, or among panicles per hill, or rice hills. The proportion of chalkiness was highest in the part of panicle base, following in the part of panicle medium, and the lowest was the part of panicle top. The chalkiness was not effected in gelatinization temperature, and not significant influence in amylose content. Amylose content was highest in the part of panicle top and decreased into the part of panicle base.

n order to conserve biodiversity and sustainable development, the research about environmental characteristics of Nelumbo nucifera, Nymphaea pubescens and Nymphoides indica was carried out in Tram Chim. The experiment was carried out from 5/2010 to 8/2010 in the different areas of Tram Chim where 3 main aquactic plants distributed. The Nelumbo nucifera lived in the environment with the soil pH ranged 3,65, soil EC was 3,23 mS/cm, the organic matter11,07%, total N 0,63 %, total P 0,13%, exchanged K 0,15 cmol/kg, free iron 0,75%, aluminium 15,54 cmol/kg. Nymphaea pubescens distributed in the soil pH 2,92, EC 3,69 mS/cm, soil organic matter 3,16%, soil total N 0,11%, total P 0,03%, exchanged K 0,05 cmol/kg, free iron 0,96%, exchanged aluminium 10,8 cmol/kg. Nymphoides indica growed in the case with soil pH ranged 3,65, EC 1,98 mS/cm, organic matter 3,99%, total N 0,17%, total P 0,05%, exchanged K 0,19 cmol/kg, free iron 0,77%, exchanged aluminium 6,78 cmol/kg. Nelumbo nucifera, Nymphaea pubescen, and Nymphoides indica adapt well in the environment with acidity and inondation

Agro? Ecological Zone, physical land suitability evaluation and economic land suitability evaluation are essential for determining of suitable crops for a region. The study was carried out in Hong Dan district, Bac Liêu province from September of 2010 to October of 2011. Interview method and land evaluation (FAO, 1976) with the use of information technology (ALES, PRIMER, IDRISI, MAPINFO) were used for evaluation and selection  effective farming models in the district. Research showed that three Agro- Ecological zones were identified as fresh, brackish and saline water. Physically land evaluation was performed, with nineteen land mapping units which were for physical land evaluation. The characteristics of Net Present Value (NPV) and Benefit per Cost ratio (B/C) were combined with results of physically land evaluation to division five Agro? Ecological Zone for nine Agro? Ecological Zone

The study was conducted to isolate the Lactobacillus sp. strains having good characteristics to produce probiotics and bacteriocin for using in striped catfish farming. Forty-five Lactobacillus sp. strains were isolated from gastrointestinal tract of striped catfish and tilapia (Oreochromis niloticus) which were sampled from Can Tho, Vinh Long, Ben Tre, Tra Vinh and Hau Giang provinces. All isolates inhibited Aeromonas hydrophila but there were 43 strains having antibacterial activity against Edwardsiella ictaluri by agar spot testing method. Among these strains, only strain Lb12 produced bacteriocin which inhibited growth of both E. ictaluri and A. hydrophila. Further experiments on Lb12 showed that in MRS broth (control medium) bacteriocin activity was 80AU/ml. However, in MRS broth supplemented with yeast extract at 2% and 3% (w/v) bacteriocin production was stimulated to 160AU/ml. The identification by sequencing of 16S ribosomal RNA gene revealed that, strain Lb12 has 100% identity to Lactobacillus suntoryeus LH5  (by BLASTN search on Genbank of NCBI). 

The quality water of intensive farming of tra-fish ponds is not accepted to release to the stream of water in river system. Therefore, many methods have been applied to treat the water of trafish ponds. Biological method was proved to be an effective method due to this practice containing bacterial strains which can concentrate suspended solid in water and removal nitrogen and phospho. In laboratory experiment, bio-liquid consisting of three good bio-flocculant bacterial strains [T2a, KT1 & P11] and three denitrifying and poly-P bacterial strains [N9b, 6Rc & LV1]) was used to treat sludge from trafish pond bottom. The results showed that the mixture of two strains [KT1 & P11] had high flocculant rate (132.58 g/l), TSS reduced from 359 mg/l to 13 mg/l and the COD decreased 1440 mg/l to 55 mg/l after 48 hours and Total ammonium TAN) & PO4- concentrations reduced to the level of lower 2 mg/l and 0.5 mg/l, respectively after 60 hours in the 10 liter jar of sludge. In larger scale (5,000 m2 area), application of bio-liquidto treat 200 m3 sludge, TSS reduced from 3,018 mg/l (initial) to 59 mg/l, COD decreased from 336 mg/l (initial) to 43 mg/l, low TAN concentration (

Bacterial leaf blight of rice, caused by Xanthomonas oryzae pv. oryzae, is a harmful disease of  rice plants that decreases the yield and the quality of rice in the planting areas. Today, there is not yet specific method to control this disease. In this study, seventy bacterial strains were isolated from samples collected in some provinces in Mekong Delta of Vietnam. Multiplex PCR technique (with two specific primer pairs) was used  to identify isolated strains (XOR-F: 5?- GCATGACGTCATCGTCCTGT-3?, XOR-R2: 5?-CTCGGAGCTATATGCCGTGC-3? and XOO290F: 5?-GCGCACCGAGTATTCCTA-3?, XOO290R: 5?-CTTCGCCGGTCCAGATGA-3?). The pair of primers XOR-F was designed to  amplify a 470bp fragment from all strains Xanthomonas oryzae pv. oryzae. The pair of primers XO290R-F was designed to amplify a 290bp fragment based on rhs  gene family of Xanthomonas oryzae pv. oryzae because these genes are structurally diverse.  Five strains were identified, they are: OM66-1, OM98, OM98-1, TL6 and AG11. Especially, one of them contains rhs gene ? a new pathogenic gene with high toxicity. When being used  for artificial infection on rice leaf, all identified strains released toxic causing disease mark with different diameters after three weeks (OM66-1: 6.78, OM98:10.33, OM98-1:4.22, TL6:6.28 và AG11:6.78(cm)).

A study on composition and population density of plankton in the coastal areas from Soc Trang to Bac Lieu province was conducted from January to December, 2008. The results showed that a total of 232 phytoplankton species belonging to 79 genera of 04 phyla was found in research areas. A number species and the percentage of Bacillariophyta, Dinophyta, Cyanobacteria and Chlorophyta was found 173 (74.57%), 54 (23.28%), 03 (1.29%) and 02 (0.86%) respectively. There were 198 species (85.34%) in the rainy season and 174 species (75%) in the dry season. A number species of Bacillariophyta was dominant in both seasons. The average concentration of chlorophyll-a was 1.67 àg/L. On the other hand, zooplankton was examined in this study, copepoda was abundant zooplankton with 105 species (42.68%), protozoa with 60 species (24.39%), Rotatoria with 31 species (12.60%), Cladocera with 24 species (9.76%) and the other with 2 to 6 species (0.81-2.44%). The average density of zooplankton was found 654 individual/m3. Density of zooplankton in the dry season was higher 2.74 time than those in the rainy season. The result indicated that copepoda was play an important role on the fluctuation a number of zooplankton in both seasons.

Intensive rice cropping with 3 crops per year may result in potassium (K) deficiency in rice if rice straw has not been incorporated or K fertilizer has not been applied. Objective of the study was to investigate soil K buffer capacity in K deficiency-risk areas in 5 samples at Cai Lay -Tien Giang and in 5 samples at Cao Lanh -Dong Thap by adding 5 levels of K to the soil samples: 0, 1,5, 3, 7,5, 15 mgK.100g-1soil. K buffer capacity was defined as the slope of Freudlich linear equation (power consant=1) between K release and K concentration in soil solution at equilibrium. Results showed that the soils had  high K supplying capacity, the amount of K supply without K addition was the same as the amount with K addition of 1,5 mgK.100g-1. K buffer capacity was high althought soils had low exchangeable K. This explained low response of rice to K fertilizer in the intensive rice cropping areas in the areas. However due to low available K in these K area, K ferilizer application should be recommended to sustain rice yield and soil K fertility.