Vol. 22 No. 8 (2024)

The pot experiment was conducted in the nethouse of the Faculty of Agronomy - Vietnam National University of Agriculture in 2022 autumn cropping seasons to evaluate the photosynthetic traits at active tillering, flowering and dough-ripen stage and grain yield at harvesting stages of four rice lines with wealthy farmer's panicle (WFP1 gene). The experimental results showed that these improved rice lines had photosynthetic rates and related characteristics such as stomatal conductance, transpiration rate and SPAD value equivalent to the control variety (IRBB) at almost the growth stages. These four lines showed a similar amount of dry matter accumulation and plant growth rate in the period from effective tillering to heading, but these parameters were surpassed the check variety in D7 line in the period from flowering to the dough-ripening stage. All improved rice lines had a significantly larger number of primary rachis per panicle (17.1-20.1), number of secondary rachis per panicle (65.7-73.2) and number of spikelets per panicle (177.6-226.4) compared with IRBB. The individual yield of three improved lines (D2, D5 and D7) was significantly higher in the range of 13.6-32.0% over than check variety. Among new lines, D7 line manifested the highest grain yield due to the largest number of spikelets per panicle, higher photosynthetic rate at the flowering stage and plant growth rate in period from flowering to the dough-ripening stage.

This study was conducted to select the promising fresh anthocyanin-rich sweet corn hybrids for national testing and commercialization in the Northern provinces. A field experiment involving thirty hybrids with two checks based on twelve important agronomic traits was performed in the 2023 Spring crop season in Hanoi. Correlation analysis showed that marketable yield was significantly positively correlated at P <0.001 with ear length (r = 0.743) and ear diameter (r = 0.717). The principal component analysis identified five important traits, viz., marketable yield, ear length, ear diameter, total soluble solids and pericarp thickness, which can be used for grouping and selecting superior hybrids. Using (Multitrait Genotype-Ideotype Distance Index (MGIDI) selection with 5% selective pressure, two superior hybrids with high commercial potential were selected, viz., THL23 (14.7 tons/ha; 18.8°Brix; 148.3mg AN /100g dry seed) and THL30 (14.0 tons/ha, 18.9°Brix; 139.4 mg AN/100g dry seed).

This study aimed to investigate the effects of eggshell powder application on the growth and physiology of robusta coffee cv. TR4 under drought stress. The experiment was a completely random designed with six rates of eggshell powder application including (A0, A1, A2, A3, A4, A5 corresponding to 0, 100, 200, 300, 400, 500kg eggshell powder ha-1) and lime application (A6) at 500kg ha-1 under the normal watering condition and drought stress condition. The result showed that drought stress condition significantly reduced growth parameters of the robusta coffee cv. TR4 such as fresh weight of roots, stems, leaves and physiological parameters such as photosynthetic rate, stomatal conductance, transpiration rate, intercellular CO2 concentration, Fv/m, the relative water content in leaves while relative ion leakage increased. Applying eggshell powder and lime increased growth and physiological parameters under both normal watering condition and drought stress condition. Higher growth and physiological parameters and lower percentage reduction of fresh weight of roots, stems, and leaves were observed in the application rate of 300kg eggshell powder ha-1.

Soft rot disease, caused by Pectobacterium spp., is one of the most dangerous pathogens causing damage to numerous crops during production, harvesting, and storage. This study aimed to isolate and classify bacteriophages from Chinese cabbage-growing soil in Lam Dong and evaluate the parasitic and lytic properties of bacteriophage isolates on Pectobacterium spp. The results revealed that 14 bacteriophage isolates were identified and assigned to six groups. The plaque morphology was characterized by a big or small inner or opaque center surrounded by a translucent outer halo of varying diameters. All 14 bacteriophage isolates had a narrow host range and were capable of lysing Pectobacterium sp. isolate DT2. Two bacteriophage isolates FDR05 and FDR07 belonging to the Podoviridae family of the Caudovirales order with a polyhedral head and a short, non-contractile tail showed high bacterial lysis ability and plaque diameters were 13.58mm and 9.37mm, respectively.

The aim of this study was to determine the presence of bacteria in Tembusu-infected duck samples collected from different provinces in Northern Vietnam. In this study, we performed PCR reactions with previously published specific primer pairs to diagnose the Tembusu virus along with E. coli, Riemerella anatipestifera, and Salmonella. The PCR diagnostic results showed that 30 out of 73 samples were positive for TMUV (41.1%). The study found that the co-infection rate of Tembusu virus with E.coli was 16.7% (5/30 samples); with Riemerella anatipestifer 20% (6/30 samples); and with Salmonella 6.7% (2/30 samples). It is noteworthy that 2 out of 30 duck samples infected with Tembusu were simultaneously infected with both E.coli and Riemerella anatipestifer, representing 6.7%. This is the first report in Vietnam to investigate the co-infection of the Tembusu virus with some common bacteria in duck flocks.

In recent years, off-white grub disease caused by metacercaria of Dollfustrema bagari has become increasingly common in channel catfish (Ictalurus punctatus) and causes great economic loss to Vietnam farmers. The study was conducted to provide more information about this parasite and serve as a premise for further epidemiological research and disease prevention. Experiments, which were conducted to assess the influence of salinity, temperature, pH on the survival time of metacercaria D. bagari. The study utilized 750 healthy flukes for this purpose. The results showed different levels of influence of the above three factors. In distilled water (salinity 0ppt; pH 6.8; 23-24°C), the metacercaria survival time is 16-18 hours. The suitable salinity for metacercaria was 0-5ppt; Flukes shrinked, died quickly within 3 hours when exposed to high salinity above 9ppt and swell in freshwater. Tapeworm larvae had the best ability to survive in the temperature range of 20-28°C (14-18 hours), while metacercaria can only survive for 3 hours out of this range. Whereas, pH did not affected visibly to metacercaria. Consequently, metacercaria D. bagari can adapt well and be more explosive in the global climate change.

The study was conducted to survey the species composition and distribution of phytoplankton in habitats at Khanh Lam 2 area in U Minh district, Ca Mau province. Samples were collected in March and August 2023 at 15 sites from 5 different habitats including (1) Forest gardens, (2) Forest plantation, (3) Fish sanctuary, (4) Mined forests and (5) Rice field. The results showed that a total of 112 phytoplankton species belonging to 5 phyla, in which Euglenophyta are more diverse and richer species composition than other major group of algae. The number of phytoplankton species at sampling sites during the study in 5 habitats ranged from 7-43 species, and the density fluctuated from 6,082-4,185,624 ind./l. The number of species and population density in the forest plantation habitat were 1.1-2.7 times and 3.2-6.3 times higher than the other habitats, respectively. The shannon (H’) diversity index was in a range of 1.58~1.96 that indicating phytoplankton diversity appears at intermediate frequencies. The accumulation rate of dominant species was Trachelomonas volvocina in 4 habitats, except the forest gardens which was recorded by Glenodinium penardii. Analysis of similarity results on species composition of phytoplankton in investigaing habitats is being clustered into 2 groups, including (1) Forest plantation and (2) Forest gardens/Fish sanctuary/Mined forests/Rice field.

This study aimed to evaluate the influence of synbiotics consisting of P. pentosaceus and Fructooligosaccharide (FOS) at different levels on growth rate, feed efficiency, and digestive enzymes of Nile tilapia. Fingerlings (mean weight of 5.78 ± 0.15g) were fed commercial pellets supplemented with only P. pentosaceus (at a density of 108 CFU/ml) served as control treatment (CT) and the treatment fish groups were fed commercial pellets supplemented with synbiotics containing P. pentosaceus (108 CFU/ml) mixed with FOS at three levels, including 0.25% (NT1), 0.5% (NT2), and 1.0% of the total amount of feed (NT3), respectively. After 60 days of the feeding trial, the results showed that the fish fed with the diets supplemented with synbiotics exhibited a better growth rate and improved feed efficiency compared to the control. Furthermore, fish fed with synbiotics significantly enhanced digestive enzyme activities compared to those in the control group (P <0.05). The results of this study suggest that using synbiotics containing P. pentosaceus and FOS at a level of 0.5% of the diet is recommended to improve the growth rate, digestive enzyme activity and feed efficiency of the Nile tilapia.

The study aimed to evaluate the current status and factors affecting N use efficiency, thereby, proposing measures for improvement to reduce N2O emissions in rice production in the Red River Delta. The experiment was conducted on 30 farmers' production fields. In each field, one plot was designed without fertilization (control). Yield and amount of N absorbed in plants were analyzed to evaluate N use efficiency indicators. The results show that the current status of N recovery efficiency from fertilizers (ANR) and agronomic efficiency (AE) were low, 22.7 ± 5.5% and 15.94 ± 3.84kg grain/kg N, respectively. The factors that affect N use efficiency included N fertilizer level, rice variety, field size, and field elevation. At the current N fertilization level of 115kg N/ha, the amount of N2O emitted directly from fertilizer ứa recorded at 12.65kg N2O/ha, equivalent to 118,151kg N2O/year across the entire rice cultivation area of Thuan Thanh district. Research scenarios of reducing N fertilizer levels by 20-40% will correspondingly reduce 20-40% the amount of N2O emissions.

Stinging nettle (Urtica dioica L.) is a medicinal plant widely used in medicine due to its content of diverse biologically active compounds. The objective of this study was to isolate endophytic bacteria (VKNS) from U. dioica L. and identify their biologically active compounds. The plant samples were surface-sterilized and placed on the nutrient agar plates. The results revealed that seven VKNS strains (LG1 to LG7) were obtained from U. dioica L, of which two strains, Bacillus cereus LG1 and Bacillus cereus LG7, had the highest ability to synthesize polyphenols (187.81 and 281.03mg GAE/l, respectively). Moreover, the research revealed that these two strains had other capabilities such as producing extracellular enzymes (amylase, cellulase, and protease), and synthesizing IAA. The supernatant of these two bacteria was resistant to most tested microbial strains and most effective at a concentration of 20 mg/ml. Furthermore, the bacterial supernatant (20 mg/ml) showed the ability to stimulate the germination of the tested seeds. Therefore, the research suggests that B. cereus LG1 and B. cereus LG7 isolated from U. dioica L. were potentially valuable sources of polyphenols. Nevertheless, further research is required to comprehend the process mechanism and achieve effective polyphenol production by endophytic bacteria.

Cellulose-degrading bacteria play an increasingly important role in the ecosystem based on their extracellular enzyme activity, which is used for treatment of plant waste. This study aimed to identify the bacteria species in the gut of earthworms that are capable of decomposing cellulose, so that bacteria can be applied to decompose agricultural by-products. 30 bacterial strains were isolated from the gut of earthworms with colony morphology mainly white, round, rod shaped cells, gram positive and hads the ability to move. Cellulolytic activity was qualified by agar well diffusion method. The results showed that 53,33% of bacterial strains were capable of degrading CMC (carboxymethyl cellulose) with the degrading ring diameter in the range of 2,67-24,67mm, bacterial strain with the strongest ability to degrade CMC was NT20 (24,67 ± 1,15mm). Bacterial cellulase activity was determined by DNS method. The result showed that bacterial strain NT20 had the ability to produce the highest reducing sugar content (50,70 ± 1,01 µg/ml) compared to the remaining bacterial strains after 48 hours of culture. NT20 bacteria had the ability to decompose 51,33% of green vegetable by-products within 10 days. The 16S rRNA gene sequence of bacterial strain NT20 was 100% similar to Bacillus amyloliquefaciens strain HT-22-B1.

This study assessed the effects of the Covid-19 pandemic on production, consumption and income of smallholder potato growers in Bong Lai ward, Que Vo town, Bac Ninh province. The research used descriptive statistics by surveying one hundred and twenty potato growers. The result showed that the incomce of smallholders’ potato growers decreased by 36.31 percent due to increase in input price, a decrease in output price, and low farm productivity (11.5 percent) in comparision with the pre-Covid period. After Covid-19, the production and distribution of farmers tend to stabilize again. The majority of the farmers adjusted to the situations by reducing market-oriented potato production towards own consumption, changing the distribution channel or selling their products at lower prices. Policy makers need to control well the pandemic, consider more supportfor production, ensure the availability of agricultural inputs to farmers at low prices and assure market-oriented strategies as well and connect farmers and enterprises in distribution.

This study aimed to assess the current status and propose solutions for agritourism development in Yen Thuy district, Hoa Binh province. The study surveyed information from 10 state management officials in tourism and agriculture, 30 tourism service businesses, and 50 tourists. The results showed that agrotourism activities in Yen Thuy district have achieved many positive outcomes in recent times, contributing to economic restructuring, increasing income for local people, promoting sustainable agriculture, and preserving local cultural values. However, agrotourism in the Yen Thuy district is still in its early stages and has not been fully exploited, with constraints such as insufficient investment capital, poor quality of human resources, inadequate infrastructure, and limited tourism products. Therefore, to develop agrotourism in Yen Thuy district in the future, it is necessary to focus on agritourism development planning; improving the quality of human resources for tourism services; investment and upgrading of infrastructure; diversification of agritourism products; and promotion of market research, advertising, and promotion of agritourism development.

The objective of the article is to review bacsic theoretical issues concerning craft village tourism. The article used information and data from domestic and international research publications. The combined results show that craft village tourism is a trend and necessary to increase income, preserve traditional culture and develop sustainable rural areas. Craft village tourism development is influenced by policies, planning, resources and characteristics of the craft villages; tourism market and demand, digital technology, community awareness and participation. Beside financial resources, the development of local businesses and the role of local authorities are also factors affecting craft village tourism. To develop craft village tourism, it is necessary to pay attention to developing the craft village tourism market and products, facilities, landscape environment and craft village space. Developing tourist routes to craft villages; developing human resources and enhancing promotion of craft village tourism brands are also important contents of craft village tourism development.