Does resource complementarity or prevention of lodging contribute to the increased productivity of rice varietal mixtures in Yunnan,China?

We conducted an experiment in Gejiu, Yunnan Province of China during the wet season of 2002 to examine the importance of resource complementarity and prevention of lodging in the fast-spreading practice of growing rice varietal mixtures in China to suppress rice blast disease and its associated damage. The hybrid rice variety Shanyou 63 and the glutinous or sticky rice variety Huangkenuo were used to study intra- and inter-varietal competition in the rice intercropping system. The experiment was laid out as a randomized complete block design in four replications with pure stands and mixtures of both varieties at different total planting densities and mixing ratios. In half of the pure stand treatments of glutinous rice a metal frame was installed to prevent lodging. The results showed that resource complementarity between the two rice varieties, resulting from niche differentiation, was marginal and did not greatly enhance the productivity of the rice varietal mixtures. In contrast, prevention of lodging of glutinous rice was identified as an important additional advantage of growing these rice varieties in mixture.     

Introgression of Xa4, Xa7 and Xa21 for resistance to bacterial blight in thermosensitive genetic male sterile rice (Oryza sativa L.) for the development of two-line hybrids

Bacterial blight (BB) of rice caused by X. oryzae pv. oryzae is a major production constraint in commercial hybrid rice production in the Philippines because most of the parental lines used in hybrid production do not carry resistance genes against the pathogen. In this study, three bacterial blight resistance genes, Xa4, Xa7 and Xa21, were introgressed to a temperature-sensitive genetic male sterile (TGMS1) line. A three-way cross of AR32-19-3-3/TGMS1//IRBB4/7 (PR36944) was made to produce 1,364 F₂ plants carrying various combinations of Xa4, Xa7 and Xa21. Individual plants were characterized for reaction to bacterial blight PXO61 (race 1), PXO86 (race 2), PXO99 (race 6) and pollen sterility. Of 144 F₂ plants demonstrating resistance against PXO61, PXO86 and PXO99, 22 exhibited highly resistant phenotypes with mean lesion lengths ranging from 0.37–2.97 cm. Analysis of disease reaction identified 20 potential TGMS F₂ plants containing Xa4, Xa7 and Xa21 while 78 plants with Xa4 + Xa7. Phenotypic and polymerase chain reaction (PCR) analyses confirmed PR36944-450, PR36944-473 and PR36944-700 as homozygous for Xa7 and Xa21 and highly resistant to all three Xoo races. Fertility of PR36944-450 and PR36944-700 was restored at permissive temperature in a growth chamber. BB-resistant TGMS lines should facilitate breeding two-line hybrids in the tropics.     

Pot2在稻瘟病菌群体结构分析中的应用

利用稻瘟病菌的一段倒位重复序列Ｐｏｔ２设计的一对引物直接对稻瘟病菌的ＤＮＡ进行ＰＣＲ扩增。根据带型相似性大于８０％为度可将国际水稻所一个稻瘟病圃上的３１０个菌株划分６个宗亲群（ｌｉｎｅａｇｅ）。这些依分子标记划分的宗亲群与品种的遗传背景有密切关系,而且各宗亲群在水稻不同生育期有不同的波动方式。     

Technical efficiency of carp production in India: a stochastic frontier production function analysis

This paper aims to examine the levels and determinants of technical efficiency in carp pond culture in India. The stochastic production frontier technique involving the model for technical inefficiency effects is applied separately to samples of semi‐intensive/intensive and extensive carp producers interviewed during 1994–95. The results showed significant technical inefficiencies in carp production in India, especially among extensive farms. The mean technical efficiencies for semi‐intensive/intensive and extensive sample farms were estimated to be 0.805 and 0.658 respectively. By operating at full technical efficiency levels, the semi‐intensive/intensive farms could, on average, increase their production from about 3.4 Mt ha^?1 to 4.1 Mt ha^?1. Likewise, the extensive farms could increase their production from 1.3 Mt ha^?1 to 1.9 Mt ha^?1. Much of these efficiency gains would come from improvement in the adoption of recommended fish, water and feed management and monitoring practices. Besides expanding production area, the results indicated several other possibilities for increasing carp production in India by increasing yields per hectare, such as: (1) increased intensification of carp culture (i.e. moving from extensive to semi‐intensive or intensive systems); (2) improvement in technical efficiency at the farm level; and (3) technological progress. However, the realization of these potentials will depend on continuous efforts by the government in ensuring an adequate supply of inputs, technology transfer and development and adequate provision of research, extension and credit services in aquaculture.     

应用分子标记技术鉴证稻瘟病菌宗谱与寄主遗传背景的亲缘关系

用散布性重复序列MGR586探针与EcoRI组合,分析广东省稻区的112个稻瘟病菌株（M.grisea）的限制性片段长度多态性（RFLPs）,根据带型相似性大于80%为度划分为15个遗传宗谱（genetic lineage）。这些在分子水平上划分的宗谱与寄主品种的遗传背景关系密切。由于广东省（包括华南稻区）大多数育成的常规稻品种和杂交稻组合在遗传背景上与GDL1及GDL2两个优势病菌宗谱寄主具有相似的共进化同缘宗亲关系,致使品种的抗性水平不高,抗性周期短暂。从而提出了选择异源供体,开展多元化育种的方向及途径。     

Macroalgal meadow habitats support fish and fisheries in diverse tropical seascapes

Canopy‐forming macroalgae can construct extensive meadow habitats in tropical seascapes occupied by fishes that span a diversity of taxa, life‐history stages and ecological roles. Our synthesis assessed whether these tropical macroalgal habitats have unique fish assemblages, provide fish nurseries and support local fisheries. We also applied a meta‐analysis of independent surveys across 23 tropical reef locations in 11 countries to examine how macroalgal canopy condition is related to the abundance of macroalgal‐associated fishes. Over 627 fish species were documented in tropical macroalgal meadows, with 218 of these taxa exhibiting higher local abundance within this habitat (cf. nearby coral reef) during at least one life‐history stage. Major overlap (40%–43%) in local fish species richness among macroalgal and seagrass or coral reef habitats suggest macroalgal meadows may provide an important habitat refuge. Moreover, the prominence of juvenile fishes suggests macroalgal meadows facilitate the triphasic life cycle of many fishes occupying diverse tropical seascapes. Correlations between macroalgal canopy structure and juvenile abundance suggests macroalgal habitat condition can influence levels of replenishment in tropical fish populations, including the majority of macroalgal‐associated fishes that are targeted by commercial, subsistence or recreational fisheries. While many macroalgal‐associated fishery species are of minor commercial value, their local importance for food and livelihood security can be substantial (e.g. up to 60% of landings in Kenyan reef fisheries). Given that macroalgal canopy condition can vary substantially with sea temperature, there is a high likelihood that climate change will impact macroalgal‐associated fish and fisheries.     

Potent interaction between thyrotropin releasing hormone (TRH) and human pancreatic growth hormone releasing factor (hpGRF) in stimulating chicken growth hormone (cGH) in vivo: Hypothalamic noradrenergic mediation in TRH stimulation of cGH release

The interaction of human pancreatic growth hormone releasing factor (hpGRF) and thyrotropin releasing hormone (TRH) on chicken growth hormone (cGH) release in vivo and possible noradrenergic involvement on TRH-induced stimulation of cGH in vivo were examined. Four-week old cockerels (1 kg) were injected intravenously with hpGRF (1.0 μg/bird), TRH (0.1 μg/bird), or hpGRF (1.0 μg/bird) in combination with TRH (0.1 μg/bird). Five min after the injection, blood samples were collected and serum concentrations of cGH were determined by a homologous RIA. The results showed that hpGRF and TRH were potent stimulators of cGH release, 5- and 6-fold over the control birds, respectively, and that hpGRF and TRH administered in combination produced a synergistic stimulation of cGH release (>20 fold). In separate experiments, pretreatment with alpha-methyl-para-tyrosine (250 mg/bird) for 2 hours resulted in complete suppression of the TRH stimulatory effect on cGH release but not the stimulatory effect of hpGRF. Pretreated with phenoxybenzamine hydrochloride (20 mg/bird) or diethyl-dithiocarbamate (500 mg/bird) also resulted in complete suppression of TRH-induced cGH release. These results indicate that hpGRF acts directly at the pituitary and TRH acts at the hypothalamus in addition to the pituitary in stimulating cGH release, possibly mediated through the noradrenergic neurons. HpGRF and TRH were potent releasers of cGH and their stimulation was potentiated when administered together.     

Magnetic resonance imaging used for the evaluation of water presence in wood plastic composite boards exposed to exterior conditions

Abstract

Two wood plastic composite (WPC) boards, one experimental and one commercial, were exposed to exterior conditions and evaluated non-destructively using a clinical magnetic resonance imaging (MRI) unit for moisture content (MC) and distribution. The experimental board was exposed in Vancouver, British Columbia, for more than 8 years, and the commercial board was exposed near Hilo, Hawaii, for 2 years. Both boards were characterized in terms of wood content, density, water uptake properties and voids content. The experimental board was additionally destructively analysed for water absorption of the WPC and MC calculated based on the wood content for verification of MRI results. MRI detected the presence of free water and its distribution in both of the WPC boards. Fibre saturation in the experimental board was found to be about 22–24%, in comparison to 25–30% present in most wood species. There was good correlation between the detection of free water by MRI and by destructive testing. Magnetic resonance images showed various major points of water entry in the WPC boards such as the support area, the cut ends, the dripping edge and the sides of the boards. For the experimental board, significant water entry also occurred at the upper exposed surface.     

Development of a Clean Biodiesel Fuel in Hong Kong Using Recycled Oil

All fuel usage produces air pollutants, causing local and trans-boundary air pollution and acid rain problems. Biodiesel is a clean renewable fuel with properties similar to diesel but produced from renewable resources such as vegetable oils and animal fats. Although this fuel has been developed some two to three decades ago, it is not commonly used, mainly due to the higher production cost involved. Due to the increasing concern on environmental protection, a lot of researches on the usage of this fuel are conducted in recent years. To study the characteristics of this fuel, a special biodiesel fuel is produced using waste cooking oil and animal fat from restaurants as feedstock. Reusing of these wastes has both the benefit of producing a cleaner fuel and waste cycling. Tests of the fuel with different proportions of diesel have been conducted on various diesel engines and the results obtained are encouraging. The environmental benefits and suitability of this fuel to Hong Kong to reduce air pollution problems are discussed based on the assessment results.     

Quantification of two polyacetylenes in Radix Ginseng and roots of related Panax species using a gas chromatography-mass spectrometric method

A sensitive method for quantitating the pharmacologically active polyacetylenes panaxynol and panaxydol in Radix Ginseng was developed using a capillary gas chromatography-mass spectrometric (GC-MS) method. The detection mode of selected ion monitoring (SIM) allowed sensitive and selective quantitation of the two compounds in ginseng. Method validation showed that the GC-MS method has much lower detection and quantitation limits than the high-performance liquid chromatography (HPLC)-UV method. This indicates that GC-MS is particularly useful for the analysis of polyacetylene compounds, which have relatively low abundances compared with ginsenosides in ginseng. Based on the quantitative results of different types of ginseng herbs, it was found that the panaxydol and panaxynol contents were higher in forest ginseng than in cultivated ginseng. This method was further applied to the quantitative analyses of panaxynol and panaxydol in Radix Notoginseng and American ginseng. The ratio of panaxydol to panaxynol can be utilized as a marker for differentiating ginseng, notoginseng, and American ginseng. This study introduces the first GC-MS method for the quantitative analysis of polyacetylenes in herbs of the Panax genus.