Vol. 20 No. 7 (2022)

This study aimed to develop and select elite anthocyanin-rich fruit corn lines for hybrid fruit corn breeding which can eat fresh without processing. Two strategies were applied viz, (i) backcross between purple waxy corn and white sweet corn, and (ii) mass selection from F2population crossed between purple waxy corn and yellow sweet corn based on morphological markers such as dark purple color and shrunken kernels. Two superior lines viz, UV10 from the first strategy and TD05 from the second strategy were selected. These lines had thin pericarp (35.2µm in UV10 line and 31.4µm in TD05), high sweetness with Brix of 17.4% in UV10 and 22.5% in TD05, and high anthocyanin content (139.9 mg/100g in UV10, and 136.9 mg/100g in TD05).Anthocyanin-rich fruit corn hybrids could be generated from a cross between purple sweet corn inbred lines and white sweet corn or with yellow sweet corn lines. Purple color in seed coat is a dominant trait and inherited to the F1generation. The marketable yield and quality of the purple sweet corn hybrids were comparable to yellow sweet corn SW1011 and predominated to purple waxy corn Fancy111, indicating the commercial potential.

The objective of study was to determine nitrogen fixing endophytic bacteriafrom Polyscias fruticosa(L.) Harms. Thirteen leaves and 11 root samples Ming aralia collected in Tri Ton district, An Giang province were used for isolating nitrogen fixing endophytic bacteria on NFB medium with free nitrogen. Results showed that the 51 isolates were isolated from leaf and root Ming aralia, in which 41 strains possessed the acidic resistance at pH 5.0. Strain LP5-L1showed highest nitrogen fixing activity, with the ammonium content of 35.3 ± 5.24 mg/l. However, strain LP1-R4 was selected for their functions to produce N, P and IAA with 31.6 ± 0.39, 18.8 ± 0.78, and 6.65 ± 0.26 mg/l, respectively. The selected strain was identified as Bacillus circulans LP1-R4 based on 16S rDNA nucleotide sequences. The efficacy of a selected strain should be evaluated for replacing N for Ming aralia in pot and field conditions.

A Randomized Complete Block Design (RCBD) study was performed for characterized on morphology and anatomy of 5 assessions of G. oppositifolius(RĐ1-RĐ5) collected in 5 provinces in Vietnam. The results showed that all assessions have similar morphological structures (roots, stems, leaves, flowers, fruits, seeds), and anatomical structures (roots, stems, leaves). But there hadsome different characteristics in adult stem color (RĐ1, RĐ2, RĐ4, RĐ5 are reddish-brown, RĐ3 is yellow-green); leaf color (RĐ3 was light green, RĐ5 was dark green, RĐ1, RĐ2, RĐ4 were green); RĐ3 assession hadthe highest values of root and leaf size (the root number was 14.60 roots/plant; the leaf length and leaf width were2.33 ± 0.02cm and 1.00 ± 0.06cm, respectively), RĐ5 assession hadthe smallest values of leaf size (the leaf length and leaf width were 1.80 ± 0.01cm and 0.51 ± 0.05cm, respectively). Anatomically, the size of the parenchyma in the stem, the libe bundle in the roots, the stem, and the main leaf veins of the RĐ3 assession hadthe largest sizes. Whereas, the RĐ5 hadthe highest value of leaf thickness (palisade mesophyll thickness was 277.8 ± 6.8µm and spongy mesophyll thickness was 198.9 ± 10.3µm).

Bovine Rotavirusis considered a major cause of diarrhea in cattle, especially in calves.This study was carried out to find the prevalence of Bovine Rotaviruscausing diarrhea in calves in Nghe An and surrounding provinces. The detection of the virus using the RT-PCR method showed that 29/142 (20.42%) stool samples of diarrhea calves were positive for Bovine Rotavirus. The positive rate of Bovine Rotaviruswas the highest in the group of calves under 1-month-old (24.75%), followed by the calf group from 2to 3 months old (10.34%). The rate ofRotavirusinfection in calves over 3 months old was rather low,only 0.08%. The VP1 gene sequencing and analysis revealed that the BRV strains isolated in the present study belonged to the R2 group, the same as the US vaccine strain MVS-BRV1 isolated in the US in 1998.

African swine fever (ASF) is a highly contagious disease with a mortality of up to 100%, resulting in high economic losses. In Vietnam, ASF was first reported in February 2019 and quickly spread to all provinces. This study aimed to estimate the basic reproduction number (R0) and developed a dynamic model to explain how ASF spreads in the pig herd during the first epidemic year to suggest vaccine coverage level required to prevent future outbreaks. The outbreak data were collected from 6 large-scale fattening farms within the first wave of ASF outbreaks. Two methods were used to estimate the R0including the Exponential Growth method (EG) and Maximum Likelihood method (ML). The average R0values were estimated at 2.97 (95%CI: 2.44-3.59) and 3.18 (95%CI: 2.52-3.96), respectively. Based on the worst-case scenario, all pigs in a herd would be infected and removed within 50 days. The vaccination rate ranges from 75-94% of pigs in each farm depending on the vaccine effectiveness.

This study was carried out to determine growth curve models for estimating live weight, weight gains and suitable slaughter age for commercial Mia chicken. A total of 300 (150 males and 150 females) birds were raised from 1 to 20 weeks of age and individual live weight data were colletced every week. Three growth functions, viz.Gompertz, Logistic, and Lopez, were used to be fitted with the growth data. The results showed that Gompertz function and Lopez function were the best models for describing the growth curves of the male and the female, respectively. The weekly gain (WGt) reached the maximum at the 10thweek and the 9thweek of age for the male and the female, respectively. The maximum of the average weekly gain (AWGt) was obtained at the 15thweek and the 14thweek of age for the male and the female, respectively.Furthermore, it was estimated that the suitable slaughter time was within 15th-16thweeks of age for the male and 14th-15thweeks for the female of Mia chicken.

The aim of this study was to determine the infection rate of Mycoplasma hyorhinisfrom suspected pigs in Khoai Chau, Van Giang, and Yen My districts of Hung Yen province.A total of 52 clinical samples of suspected pigs were used to determine the infection rate of M. hyorhinisby using the PCR method. The results showed that the infection rate of M. hyorhinisin 3 districts in Hung Yen province was relatively high at 26.92%, in which infection rate was recorded in Khoai Chau with 31.82%, Van Giang 25.00% and Yen My 21.43%. The rate of infection with M. hyorhinisin pigs at 5-10 weeks of age was the highest at 29.41% and was similar to pigs >10 weeks old 28.57%,while pigs <5 weeks oldshowed lowest infection rate 21.43%. Research also determined that the rate of co-infection of M. hyorhiniswith M. hyopneumoniaeaccounted for 28.57%, H. parasuis35.71% and S. suis21.43%. Comparison of macroscopic findings and PCR results showed that pigs infected with M. hyorhinisexhibited the main pathological feature with a severe fibrinous pericarditis.

This study was conducted with the aim of providing a farming procedure with appropriate technical criteria applicable to Hai Phong and Northern provinces. Stocking density in phase 1 was 150 juveniles/m2for the period of 50 days. Phase 2 was started with two different stocking densities: 15 prawns/m2and 20 prawns/m2, two replica for each for the same culture time of 134 days. The results show that the water quality in cultured system including water temperature, water pH, transparency, dissolved oxygen, NH3, NO2and H2S, aerobic total bacteria, Aeromonas, Pseudomonas, phytoplankton was in the acceptable limit for the growth of giant freshwater prawn. The survival rate of phases 1 reached 80% after 50 days. In phases 2 after 134 days, the survival rate and harvested size of prawns for the density of 15 and 20 prawns/m2 were 71% and 80.93 g/prawns; 68.5% and 76.96 g/prawns, respectively. Culture of all-male giant freshwater shrimp in two-phase with stocking density of 15-20 prawns/m2obtained high efficiency and could be applied to production.

This study was conducted with the aim of providing a farming procedure with appropriate technical criteria applicable to Hai Phong and Northern provinces. Stocking density in phase 1 was 150 juveniles/m2for the period of 50 days. Phase 2 was started with two different stocking densities: 15 prawns/m2and 20 prawns/m2, two replica for each for the same culture time of 134 days. The results show that the water quality in cultured system including water temperature, water pH, transparency, dissolved oxygen, NH3, NO2and H2S, aerobic total bacteria, Aeromonas, Pseudomonas, phytoplankton was in the acceptable limit for the growth of giant freshwater prawn. The survival rate of phases 1 reached 80% after 50 days. In phases 2 after 134 days, the survival rate and harvested size of prawns for the density of 15 and 20 prawns/m2 were 71% and 80.93 g/prawns; 68.5% and 76.96 g/prawns, respectively. Culture of all-male giant freshwater shrimp in two-phase with stocking density of 15-20 prawns/m2obtained high efficiency and could be applied to production.

Agaricus blazei Murill is a medicinal mushroom with potent immunomodulatory and antitumor activities. Nutrition and environmental conditions are two main factors affecting the mycelial growth of mushrooms. Therefore, the study was carried out to optimize the culture of Agaricus blazei on a pure cultural medium. The carbon sources (glucose, fructose, maltose, sucrose, and lactose), nitrogen sources (NH4Cl, NH4NO3, (NH4)2SO4, NH4HPO4, peptone, and yeast extract) with initial pH values ​​of 4, 5, 6, 7, 8, 9 and incubation temperatures of 15C, 20C, 25C, 30C, and 35C were tested for mycelial growth of Agaricus blazei mushroom strain Ab-1. The mycelial colony diameter, growth rate, and mycelial density were evaluated with P <0.05. Results indicated that glucose and yeast extracts were the most suitable carbon and nitrogen sources for the mycelial growth of strain Ab-1. pH6 and temperature of 25C were also optimal conditions for the growth of Ab-1 mycelia. The mycelial colony's growth rate and diameter reached 8.14 mm/day and 78.44 mm after 10 days.

Diseases caused by pathogenic fungi account for 80% of plant diseases resulting in a global crop yieldreduction. The use of chemical fungicides for the control of fungal diseases causes environmental pollution and affects human health. Biocontrol using actinomycetes having antifungal activity was reported to be effective and biosafe. This studyfound that actinomycete strain VNUA30 exhibited a broad-spectrum antifungal activity against five plant pathogenic fungi, i.e. Colletotrichum gloeosporioides, Fusarium oxysporumf.sp. cubense(FocTR4), Corynespora casiicola, Sclerotium rolfsii, and Diaporthe sp. with inhibition rate of 62.50%; 52.58%; 72.22%; 57.77%; and 95.37%, respectively. Biological studies showed that strain VNUA30 was able to produce melanoid pigment, siderophore, H2S and IAA, assimilate citrate, reduce nitrate, liquefy gelatin, degrade urea and produce extracellular enzymes chitinase, cellulase, xylanase, protease, and pectinase. Combining the morphological and biochemical characteristics with the 16S rRNA sequence analysis, this strain was identified as Streptomyces deccanensis VNUA30. The results confirmed that actinomycete strain VNUA30 is a potential strain as bio-control agent for fungal diseases on plants with high efficiency.

The study determined the Total Factor Productivity Growth and decomposed the source of the contribution to total factor productivity growth of rice farming households in the Mekong Delta. Based on a panel data collected in the first survey in 2017 and repeated survey in 2019 from273 Jasmine ricefarmers, the Cobb-Douglasstochastic frontier production functionincorporating inefficiency effects was employed to analyze the data byusing theFrontier 4.1.The results revealed thatthetotal factor productivity growth was15.31% in the whole period of2017-2019, equivalent to 7.66% per year. Sources of total factor productivity growthin this period consisted of technological change (2.11% points), scale efficiency change (14.43% points) and technical efficiency change(-1.23% points).

Chicken production remains as an important economic activity that is unlikely to change in the near future in Vietnam, especially in rural areas like Soc Son. This study aimed to develop broiler production in the district in the coming time. This study utilized data collected from the Economic Division of Soc Son District and surveyed 103 chicken farming households in Soc Son District. Data analysis consisted of descriptive and comparative statistics.Exploratory factor analysis with Likert scale and regression analysis were also used in the study. Research results showed that chicken production in Soc Son district in recent years developed rapidly and generated income to farmers. Factors affecting the development of chicken production of households in Soc Son district included awareness of farmers, household resources, market for selling the product, infrastructure and government policies.

This study aimed to assess the current situation and propose solutions to mobilize capital for investment in the transport infrastructure of Hoa Binh province in the coming period. Descriptive statistics and comparative methods were used to analyze the secondary data and survey data of 50 state managers at all levels, 10 enterprises, and 150 representative residents of Hoa Binh province. The study showed that investment in the transport infrastructure development of Hoa Binh province had positively contributed to the local socio-economic development, promoting the transport and circulation of goods, improving rural infrastructure, speeding up the process of building new countryside, and alleviating poverty. However, the capital source for transport infrastructure investment was mainly from public investment capital, not diversified, and investment capital limited from the private sector in the 2016-2020 period. The disbursement progress of some projects was still slow and investment norms were low, so investment efficiency was not high and unsustainable.