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排序方式: 共有189条查询结果,搜索用时 203 毫秒
61.
Hue Thi Nguyen Quang Hong Vu Tan Van Mai Thu Thi Nguyen Lam Duc Vu Tung Thanh Nguyen Long Viet Nguyen Hien Thu Thi Vu Hue Thi Nong Trung Nguyen Dinh Nakano Toshitsugu Liet Van Vu 《水稻科学》2018,25(1):52-56
Bacterial leaf blight of rice (BLB), caused by Xanthomonas oryzae pv. oryzae, is one of the most destructive diseases in Asian rice fields. A high-quality rice variety, LT2, was used as the recipient parent. IRBB21, which carries the Xa21 gene, was used as the donor parent. The resistance gene Xa21 was introduced into LT2 by marker-assisted backcrossing. Three Xoo races were used to inoculate the improved lines following the clipping method. Eleven BC3F3 lines carrying Xa21 were obtained based on molecular markers and agronomic performance. The 11 lines were then inoculated with the three Xoo races. All the 11 improved lines showed better resistance to BLB than the recipient parent LT2. Based on the level of resistance to BLB and their agronomic performance, five lines (BC3F3 5.1.5.1, BC3F3 5.1.5.12, BC3F3 8.5.6.44, BC3F3 9.5.4.1 and BC3F3 9.5.4.23) were selected as the most promising for commercial release. These improved lines could contribute to rice production in terms of food security. 相似文献
62.
Despite the growth of aquaculture exports from developing countries to developed countries in recent years, a high percentage of these products are rejected at developed countries’ ports because of non-compliance with international standards. This paper presents a case study of the shrimp aquaculture sector in Vietnam to examine the factors behind the persistence of such port rejections. In particular, we focus on why the so-called better management practices (BMPs) are not appropriately adopted by many farmers and examine whether the number and types of information sources matter in farmers’ decisions on BMP adoption and whether BMP adoption actually leads to better performances. On the basis of our estimation using primary data collected in Southern Vietnam, we find that information sources and training experiences indeed matter in the adoption of a higher number of BMPs and that BMP adoption indeed reduces the possibility of disease outbreaks. These results prove the effectiveness of BMPs and suggest the importance of disseminating knowledge regarding them to farmers through experts. 相似文献
63.
Dinh Duy Vu Thi Tuyet Xuan Bui Minh Tam Nguyen Dinh Giap Vu Minh Duc Nguyen Van Thang Bui Xiaohua Huang Yi Zhang 《林业研究》2017,28(2):265-272
Taxus chinensis and T. wallichiana in have been threatened in their distribution areas in recent decades because of their over-exploitation and reduction and destruction of native habitats. Determining the genetic diversity in populations of the two species will provide guidelines for their protection and preservation. Two hundred and fifteen trees from six populations of T. chinensis and 150 sampled trees of T. wallichiana were sampled. Six microsatellite primer pairs selected from 16 primer pairs were used to investigate genetic variation at the population and species levels. Five yielded polymorphic alleles, and among the 13 putative alleles amplified, 11 were polymorphic (accounting for 76.33 %).Shannon’s information index (I) and percentage of polymorphic bands (PPB) (I = 0.202 and PPB = 67.22 % for T. chinensis; I = 0.217 and PPB = 65.03 % for T. wallichiana). Both species had low levels of genetic diversity (mean H o = 0.107, H e = 0.121 for T. chinensis; H o = 0.095, H e = 0.109 for T. wallichiana). Genetic differentiation among populations was higher (F ST = 0.189) for T. chinensis and lower (0.156) for T. wallichiana, indicating limited gene flow (Nm) among populations for T. chinensis (0.68) and T. wallichiana (0.65). Variation among individuals of T. chinensis was 63.59 and 73.12 % for T. wallichiana. Thus, the threatened status of the two conifers is related to a lack of genetic diversity. All populations are isolated in small forest remnants. An ex situ conservation site should be established with a new population for these species that comprises all the genetic groups for the best chance to improve their fitness under environmental stresses. 相似文献
64.
Neglected and underutilized species (NUS) play a pivotal role in the improvement of nutrition, medicine, and income for rural populations in the Northern mountainous provinces of Vietnam. PRA and baseline tools were used to collect the ethnobotany information of the NUS and their practical uses through the traditional knowledge of a local culture and people in the three Northern mountainous provinces of Vietnam. The results showed noticeable values of seventy-seven NUS including 50 leafy vegetables, 9 root and tuber crops, 11 edible wild fruits, 3 legumes and 4 others (some species have defined as NUS, others have not yet defined as NUS). These findings would create a strong promotion for utilizing and conserving of genetic resources of NUS in the Northern mountainous regions of Vietnam. 相似文献
65.
Dang Quoc Thuyet Thai Quoc Hien Hirozumi Watanabe Hirotaka Saito Thai Khanh Phong Taku Nishimura 《Paddy and Water Environment》2010,8(3):235-245
The micro paddy lysimeter (MPL) was developed and evaluated for its performance to simulate solute transport in paddy environment
under laboratory conditions. MPLs were constructed using soil collected from Field Museum Honmachi of Tokyo University of
Agriculture and Technology, Japan. For the physical characteristics of the hardpan layer, parameters such as thickness, and
soil aggregate size, affecting the percolation rate were studied. For the plow layer, two types of plow soils, sieved and
un-sieved soils were compared. The sieved soil plow layer was produced by mixing air-dried soils of different aggregate sizes
of D > 9.50, 9.50 ≥ D > 4.75, 4.75 ≥ D > 2.0 mm and D ≤ 2.0 mm at 47.1, 19.5, 20.6, and 12.8%, respectively. The un-sieved plow layer soil was directly used after collecting from
the field. Inert tracer was applied to ponding water with controlled boundary conditions to evaluate the reproducibility of
the soil hydraulic characteristics. HYDRUS-1D was used to evaluate the movement of bromide tracer in the MPL. The proposed
conditions of the MPL were that the hardpan layer can be made from soil aggregates smaller than 0.425 mm with 2 cm thickness
and that the plow layer can be prepared with sieved or un-sieved soils. With these conditions, the obtained results proved
that MPLs can be a useful tool to simulate solute transport in paddy environment. 相似文献
66.
Min B. Rayamajhi Paul D. Pratt Ted D. Center Thai K. Van 《European Journal of Forest Research》2010,129(6):1155-1168
The exotic tree Melaleuca quinquenervia (melaleuca) forms dense forests usually characterized by low plant diversities and dense litter biomass accumulations on
forest floors of ecologically sensitive ecosystems, including portions of the Florida Everglades. We quantified litter accumulation
in mature melaleuca stands and compared decomposition rates of melaleuca leaves with a sympatric native plant, either Cladium jamaicense (sawgrass) in sawgrass marshes or Pinus
elliottii (slash pine) in pine flatwoods habitats that varied in soil types. Total litter accumulation in mature melaleuca forests
prior to June 1997 ranged from 12.27 to 25.63 Mg ha−1. Overall, melaleuca leaves decomposed faster in organically rich versus arenaceous soils. Decomposition rates were lower
for melaleuca leaves than for sawgrass in both melaleuca-invaded and uninvaded sawgrass marshes. In arenaceous soils of pine
flatwoods, melaleuca leaf and pine needle decomposition rates were similar. Complete mineralization of sawgrass leaves occurred
after 258 weeks, whereas melaleuca leaves had up to 14% and pine foliage had up to 19% of the original biomass remaining after
322 weeks. Total carbon (C) in intact decomposing leaves varied slightly, but total nitrogen (N) steadily increased for all
three species; the greatest being a fourfold in sawgrass. Increases in N concentrations caused decreases in the C/N ratios
of all species but remained within an optimal range (20–30) in sawgrass resulting in higher decomposition rates compared to
melaleuca leaves and pine needles (C/N ratio >30). Slower decomposition of melaleuca leaves results in denser litter layers
that may negatively affect recruitment of other plant species and impede their establishment in invaded communities. 相似文献
67.
68.
Analytical methods for the determination of trifloxystrobin and four of its metabolites were developed in a leaching study conducted in Hawaii. To duplicate plots at each of five locations representing various agricultural areas in Hawaii, trifloxystrobin was applied at label rates and allowed to leach under normal rain and irrigation conditions. Soil samples were collected at weekly to monthly intervals and the residual concentrations of trifloxystrobin and metabolites measured. A quantitative analytical method for their determination in various soil samples was developed using accelerated solvent extraction (ASE), coupled with liquid chromatography-tandem mass spectrometry. Extraction solvent with various ratios of methanol to water, addition of EDTANa2 to the extract solvent, and ASE cell temperature were adjusted to improve recovery. Deuterated (E, E)-trifloxystrobin was chosen as the internal standard of the analytical method. The limit of quantitation was 2.5 ppb in the soil for trifloxystrobin and its metabolites. Laboratory aerobic degradation studies with the soils from the five sites were also conducted to measure the same compounds. 相似文献
69.
Stanislav Trdan Filip Vučajnk Tanja Bohinc Matej Vidrih 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2019,69(1):89-94
In 2017, we conducted a field experiment to test the influence of a mixture of two plant growth-promoting bacteria (Pseudomonas fluorescens and Azospirillum brasilense) on the yield of three potato varieties. In addition, the influence of the mixture on potato susceptibility to infection by the pseudofungus Phytophthora infestans and fungus Alternaria solani and to attacks by the Colorado potato beetle (Leptinotarsa decemlineata) was investigated. It was the first experiment of its kind in Europe. In the unusually hot and dry year, a positive influence on the yield (17%–31%) was found in all three varieties when the tubers were soaked in the bacterial mixture prior to sowing. We observed no significant differences in potato resilience/susceptibility to harmful organisms among the different treatments (soaked tubers, sprayed tubers, untreated tubers); however, there were significant differences in the productivity between the tuber varieties. The results of our research indicate the bacterial mixture used in this study has a high potential to support satisfactory potato yields under dry conditions and under low levels of infection by foliar fungal diseases and attacks by foliar insects. 相似文献
70.
Mitsuo Nyuji Tetsuro Shiraishi Sethu Selvaraj Vu Van In Hajime Kitano Akihiko Yamaguchi Kumiko Okamoto Shizumasa Onoue Akio Shimizu Michiya Matsuyama 《Fisheries Science》2011,77(5):731-739
The physiological functions of pituitary gonadotropins (GtHs) are well established in higher vertebrates, whereas those in
teleosts are still poorly understood. To describe the role of GtHs during gonadal development of female chub mackerel Scomber japonicus, changes in follicle-stimulating hormone (FSH) and luteinizing hormone (LH) cells were investigated immunohistochemically
during the seasonal reproductive and spawning cycles. FSH and LH cells were identified in the different cell types of the
proximal pars distalis (PPD); FSH cells were located in the central PPD, whereas LH cells were localized along the border
of the pars intermedia. To examine changes in FSH and LH cells, the percentage of FSH or LH cell-occupying area in the PPD
was evaluated and represented as FSHβ-immunoreactive (ir) or LHβ-ir levels, respectively. FSHβ-ir levels increased significantly
from immature to the completion of vitellogenesis, whereas LHβ-ir levels were maintained at high levels from early vitellogenesis
to post-spawning. During the spawning cycle, which consisted of four stages from just after spawning to the next oocyte maturation,
both FSHβ-ir and LHβ-ir levels showed no significant changes among different stages; however, LHβ-ir levels remained relatively
high, and FSHβ-ir levels were constantly low. These results suggest that both FSH and LH may be involved in vitellogenesis
and LH may act at final oocyte maturation in female chub mackerel, although the role of FSH during the spawning cycle is still
unclear. 相似文献