Vol. 16 No. 3 (2018)

Backcrossbreedingwas used with the aim to improve the sweetness of purpleand white waxy corn materials at VietnamNational University of Agriculture. The F1 ofspring between waxy corn with sweet corn was backcrossed with waxy corn for two generations (BC2F1). The backcrossing progeny underwent 3 generations of selfing to BC2F4 to recover the waxy corn genetic background. Evaluation and selection of BC2F4 waxy-sweet corn were done in 2017 spring season in Gia Lam, Hanoi. Phenotypic data were measured for growth and developmental characteristics, yield and yield components, total anthocyanin content, pericarp thickness, sugar content and eating quality. Elite corn lines were selected based on selection index computed from ideotype plant analysis involving 10 studied traits. Twenty best performing elite lines were identified for use in inbred line development program. Backcrossing method has remarkably improved the sweetness of waxy corn by 0.3 to 4.0 percent. Backcrossing method, therefore, can be used to enhance the sweetness of waxy corn in Vietnam.

The aim of study was to improve the nutritional quality of cassava residues by means of simultaneous saccharification and fermentation. Cassava residues were mixed with water at the rate of 30% and saccharification was carried out with crude enzymes (α-amylase, glucoamylase, cellulase) at different concentrations (0, 2, 4, 6, 8, 10%). After 24 hours, at 8 and 10% crude enzymes, the reducing sugar was highest while the starch and crude fiber content were lowest. Simultaneous saccharification and liquid fermentationof cassava residues were conducted in 3L fermenters supplemented with 8% enzyme, 1% (NH4)2SO4and S. cerevisiae, Lactobacillus sp., and Bacillus sp. (107cfu/ml of each) at room temperature. After 48 hours fermentation the crude protein increased by 7.3 times and real protein increased by 5.5 times compared with unfermented cassava residues, while HCN decreased to 20.54 mg/kg, organic acid increased by 5.9 times, pH value was 3.7. The fermented product had good flavor, slight acidity and no aflatoxin.

This study aimed to investigate the proteolytic enzyme activity of mud crab (Scylla paramamosain) larvae and crablets. Samples of crab larvae fed live feed (artemia) were collected at various stages from Zoae-1 to Crab 1. Protease, trypsin, chymotrypsin and pepsin activity were analysed during larval development stages. The results showed that protease and pepsin activity increased regularly (at 3,85 - 19,1 U/mg protein and 1,69 - 8,32 U/mg protein, respectively) during lavral stage while trypsin and chymotrypsin activity were low from Zoae-1 to Zoae-5, particularly strongly fluctuated at Zoae-5, Megalope, and Crab stage. The protein hydrolyzed enzymes (protease, trypsin, chymotrypsin and pepsin) started with very low activities at the early stages (Zoae-1 to Zoae-3) and increased significantly from Zoae-5 to crablet stage when the digestive system of mud crab completely developed. The findings indicated that the proteolytic enzyme activities of mud crab varied during the stages of larval development.

Thirty-five piglets aged from 1 to 4 weeks were collected from wild pigfarms in Ha Giang province. The RT-PCR was used to confirm porcine epidemic diarrhea (PED) virus. The results showedthat the proportion of positive samples was74.3% and 54.3% for small intestine and mesenteric lymph node andfor fecal samples, respectively. The main clinical signs of PED included weakness, depression, and diarrhea with loose, fishy, and yellow stools (100%)andweight loss (80.8%). Suckling pigs showed anorexia, huddling together, laying on the sow (76.9%), dehydration (69.2%), loss of appetite (57.7%), hypothermia and heaving (53.8%).The autopsies showed distended stomach containing curd and undigested food (100%),thinness of the wall of small intestine and watery yellow translucent content in small intestine (100.0%),hyperemia and hemorrhage of mesenteric lymph nodes (80.8%),enlargement of lymph nodes in other organs (69.2%); pale liver (69.2%),pneumonia (61.5%),splenic congestion, and gallbladder enlargement (57.7%). Microscopic lesions included small intestinal congestion, hemorrhage, severe villous atrophy, scraped mucosa, lymphoid follicles hyperplasia, inflammatory cell infiltration, degeneration, and necrosis. Congestion and inflammatory cells infiltration were observed in liver, spleen, and lung. In addition, hepatocellular degeneration and lipid deposition were observed in the liver.

In this study, fifteen microsatellite markers were used to optimize a protocol for analyzing genetic diversityof pompano (Trachinotusspp.). Seven single markers were successfully optimized for short fin Pompano and four markers were optimized for long fin pompano. Three multiplex PCR reactionsincludingtwo multiplex pools for short fin Pompano and one pool for long fin pompano were developed which composed of nine fluorescent-labeled markers. Fragment analysis process was successfully established with three pools of microsatellite markerscorresponding to nine loci. Genotyping results revealedpolymorphism in eight loci (EC-7; EC-9; EC-10; EC-17; EC-20; EC-28; TB018; TBG030) with the number of alleles rangingfrom 3 to 6, whereas locus TO67 showed monomorphisms. Thesefindingsimportantlycontributeto the understanding of genetic diversity in pompano.

The objective of the present study was to determine the effects of different protein contents in feedon the maturationand reproductive efficiency of black apple snail (Pila polita). Snail broodstocks were fed with 5 protein levels with triplicates for each as follow:15% (P15); 20% (P20); 25% (P25); 30% (P30) and 35% (P35). The broodstockswith shell height of 36.2 - 44.8 mm were reared in the tarpaulin tanks (1 × 1 × 1 m) atthe density of 60 individuals/tank and male: female ratio was 1: 1. After 90 days of culture, mean GSI of snails in P25 (13.90% in female; 5.10% in male) was higher than that of P20 (12.66%; 4.14%) and significantlydifferent(P < 0.05) with P15 (8.27%; 3.59%). Spawning frequency of broodstocks in P25 (1.06 clutch/week/m2), P20 (0.78 clutch/week/m2) wassignificantlydifferent(P < 0.05) compared to those in P15 (0.44 clutch/week/m2), P30 (0.61 clutch/week/m2) or P35 (0.47 clutch/week/m2). Snails in P25 also had the highest reproduction efficiency (206 eggs/clutch), P30 (189 eggs/clutch) and significantlydifferent(P < 0.05) from P15 (124 eggs/clutch), P20 (175 eggs/clutch) and P35 (154 eggs/clutch). The results showedthat processed foods with a protein content of 25% yieldedhigher maturity rate and reproductionefficiencyof black apple snail compared to other protein contentsin feed.

Clam broodstocksGeloinasp were collected at U Minh Thuong areas, Kien Giang province to investigatethe effects of different spawning methods on efficiencyin the hatchery. The study consisted of3 experiments: 1) Using chemicals, 2) Changing temperature and 3) combining chemicals and temperature changes. Several indicators such as number of reproductive individuals, reproductive rate, survival, effective time and the numbers of eggs were significantly differentamong treatments (P < 0.05). Results showed that lowering temperature combined withflow through water system was most suitable for clam spawning withr 50%efficiency, high eggs/individual (1.203.000 ± 199.983)andshorter spawning time..

Porcine Epidemic Diarrhea Virus(PEDV) causesacute diarrhea in pigs and this is especially dangerous for piglets. Isolation of PEDV is a pre-requisite for research on production of vaccinesor bioformulationsin the prevention and treatment of the disease.Small intestinesof pigs diagnosed positively with PEDV based on RT-PCR method and vero cell lines were used for this study. PEDV isolationswere determined for the viral titre and the growth curve. A total of 13 PEDV strains were successfully isolated from83diseasesamples. The medium containing 10µg/ml trypsinwas suitable for viral isolation. PEDV was permissive for replication and caused disease at the beginning ofthe second culture passage. Infected vero cell cultures exhibited characteristics CPE by cell-fusion and syncytial formation. CPE occured at 12 hours post infection and the cellswerecompletely destroyed after 36 to 48 hours of infection. In thefirst passage,CPE viral titre ranged from 103,4to 105,7TCID50/mlbut after4 culture passages,theviral titre increasedfrom 105,3 to 107,3TCID50/ml.

The effect of slow-release fertilizers(SRF) on growth, development and yield of NK66 hybrid maize was studied in 2013 and 2014springcropping seasons, in Bat Xat district, Lao Cai province. The effect of different types of SRFproduced by using organic polimer and nitrogen release inhibitorwere comparedwith common chemical fertilizer (nitrogen, phosphorous and potassium). All treatments were applied with 110N + 60P2O5 + 57K2O per hectare. The experiment was arranged in a randomized complete block design (RCBD) with three replicationsanf the corn variety was NK66 planted at density of 57,000/ha. The study results showed that the SRF application has positive effect on growthanddevelopment of corn. Grain yield varried from 6,803 ton/ha to 7,975 ton/haand SRF with coating polymer and plant extract had the highest yield.

Perilla leaves and the essential oil have been used in food and traditional medicine for a long time. The essential oil from perilla leaves was proven to be the most active components attributable to the health benefits. This study aimed to determine the most suitable condition for the extractionof essential oil from perilla leaves (0.76 % essential oil) by using steam distillation technology. The perilla leaves were distillated within 48 h after harvest with leaf cut pieces of of 2.0 < d 4.0 mm in size. The optimum distillation conditions were determined as follows: vapor pressure 2 atm, sample to distillation chamber volume ratio 0.4 kg/l, distillation rate 30%, condensation temperature 40 0C, and distillation time 180 minutes. Under these conditions, the distillation yield was 95.35%. The obtained essential oil had typical flavor of perilla with 38.99% perilla aldehyde, 23.71% perilla alcohol, 6.22% -zingiberene and 5.63% β-caryophylene, which can be used as fragrances in food and pharmaceutical products.