水稻品种多样性持续控制稻瘟病研究

在对水稻品种进行抗病基因同源序列RGA(Resistance gene analogue)分析的基础上,应用品种多样性有利于病菌稳定化选择原理,选择抗性遗传背景差异大的品种,在吉安和石城进行混合间栽防治稻瘟病研究。不同年份不同生态环境下试验均表明,遗传背景差异大的水稻品种混合间栽,对稻瘟病有明显控制效果,特别是感病优质糯稻品种混合问栽后,稻瘟病发病率、病情指数均极显著下降,其防治效果达82．14％～95．91％。混合间栽对杂交稻稻瘟病也有一定控制效果,防治效果为40.82％～70．87％。与净栽相比,水稻产量增幅在6．03％～11．81％之间。     

Studies on sampling schemes for the establishment of corecollection of rice landraces in Yunnan, China

The sampling scheme for a core collection from the basecollection of Yunnan rice landraces was studied, using 6,121accessions catalogued in the national genebank and 31 charactersincluding taxonomic characters, morphological characters andagronomic characters. Sampling scheme was studied at three levels,i.e., grouping principle, sampling proportion within group andsampling method from each group. Grouping principles used wereDingying's taxonomic system, Cheng-Wang taxonomic system,Yunnan rice ecological zone, Yunnan administrative district, singlecharacter and completely random sampling without grouping. Samplingproportions in each of the groups were square root, logarithm, indexof genetic diversity and fixed proportion. Clustered and randomsampling were carried out in each group. Five parameters, (indexof genetic diversity, variance of phenotypic value, variance ofphenotypic frequency, coefficient of variation and ratio ofphenotypic retained), in primary core collection were used toevaluate the validity of sampling scheme. The better samplingstrategies were grouping principles based on the two taxonomicsystems, decisions on sampling proportion in each group based onsquare root or logarithm, sampling method within group clustered.16%, 10% and 5% overall sampling ratio were usedto establish primary core collections. The results showed that a510% sampling ratio was suitable for a largecollection.     

Participatory landrace selection for on-farm conservation: An example from the Central Valleys of Oaxaca, Mexico

On-farm conservation is recognized as a key component of a comprehensive strategy to conserve crop genetic resources. A fundamental problem faced by any on-farm conservation project is the identification of crop populations on which efforts should be focused. This paper describes a method to identify a subset of landraces for further conservation efforts from a larger collection representing the diversity found in the Central Valleys of Oaxaca, Mexico. Mexico is a center of origin and diversity for maize (Zea mays L.). The 17 landraces selected from an initial collection of 152 satisfy two criteria. First, they represent the diversity present in the larger collection. Second, they appear to serve the interests of farmers in the region. Data for applying the method were elicited through participatory as well as conventional techniques. They incorporate the complementary perspectives of both men and women members of farm households, and of plant breeders and social scientists.     

The extinction of genetic resources of Asian wild rice, Oryza rufipogon Griff.: A case study in Thailand

Natural populations of wild rice, Oryza rufipogon Griff., are now threatened with the disturbance of their natural habitats by various human activities. To obtain basic information on genetic erosion or loss of genetic diversity in wild rice, we investigated how environmental changes of habitat affected the genetic structure of its natural population at a study site in the central plain of Thailand. During 10 years from 1985 to 1994, the wild-rice population at this site was seriously destroyed and fragmented. Using two sets of seed sample collected in 1985 and 1994 from the same population, allozyme variability at 17 loci of 11 enzymes were examined. Isozyme genotypes of mother plants of seed samples were estimated by the segregation in each progeny, and we calculated genetic parameters for the population. Gene diversity severely decreased in the 1994 sample compared with the 1985 sample. It is supposed that declining and fragmentation of the wild rice population, which happened during the 10 years, caused loss of genetic variability and forced the habitually outbreeding plants to inbreed, accelerating a reduction in gene variability. Pgi1-1 allele which was common in Indica rice cultivars of this region was found in the wild rice plants growing at the side of rice fields. Probably, introgression has occurred between wild and cultivated rice plants, and consequently the intrinsic nature of wild rice was gradually blurred by cultivar genes. We must realize that the genetic erosion of wild rice is rapidly proceeding and that an action for their conservation in natural environment, so called in situ conservation, is urgently needed.     

近地层臭氧浓度升高对稻田土壤微生物群落功能多样性的影响

利用中国臭氧FACE(Free-Air O3 Concentration Enrichment,开放式空气臭氧浓度增高)试验平台,研究了近地层臭氧浓度升高条件下,2009年和2010年的稻田土壤微生物功能多样性的响应规律。结果发现,1.5倍当前臭氧浓度下稻田土壤水溶性有机碳含量从100.0～110.9μg g-1降低至81.3～94.5μg g-1。臭氧浓度升高下BIOLOG平均吸光值(AWCD)有低于对照的趋势。多样性指数结果表明,臭氧浓度升高50%对稻田土壤微生物丰富度、优势度及均一度无显著影响。2010年碳源底物利用的主成分分析显示,1.5倍当前臭氧浓度下稻田土壤微生物对碳源底物的利用方式发生变化。本研究揭示近地层臭氧浓度升高可能对稻田土壤微生物产生积累效应,并通过微生物碳源底物有效性的改变最终影响土壤微生物的功能多样性。     

A Suitable Site for in situ (On-farm) Management of Plant Diversity in Traditional Agroecosystems of Western Himalaya in Uttaranchal State: A Case Study

There is a growing realisation world over that the introduction of modern agriculture has to be supplemented with measures to conserve biodiversity in situ if yield gains are to be stabilized. Hence, there is a growing interest from agricultural development specialists and conservation biologists for understanding the socioeconomic factors determining the conservation of biodiversity in situ. The present study was conducted with the objective of understanding the in situ (on-farm) conservation of agrobiodiversity in traditional agroecosystems taking the Urgam valley in north-western Himalaya of India, as a case study. An inventory was made of traditional crops and wild economic species for subsistence, and the structure of forest resource base, traditional knowledge related to resource management and use. Institutional and scientific challenges for in situ (on-farm) management of crop diversity were studied and are discussed in this paper. Complementarity of in situ (on-farm) conservation with ex situ conservation together with crop improvement in such marginal areas are suggested.     

Rice genetic diversity at farm and village levels and genetic structure of local varieties reveal need for in situ conservation

Rice genetic diversity partitioning between farms, varieties and, within-variety diversity, were analysed in two villages of Maritime Guinea with contrasted agroecological conditions. One thousand and two hundred individual plants belonging to 45 accessions collected in eight farms were genotyped using 10 SSR markers. The molecular variance was evenly shared between and within accessions, while the farm effect was almost nil. Local varieties had a multi-line genetic structure. The number of multilocus genotypes was proportional to the utilisation rate of the variety in the village. The F _ST values between different accessions of each variety were significant which indicated low genetic consistency in the variety names. This varietal structure could mainly be explained by the migration phenomenon and the high varietal turnover. Compared to allelic diversity, multilocus genotypic diversity seemed to be the most suitable indicator of the quantitative distribution of diversity at different management scales (accession, farm and village). The within- and between-farm F _ST values were in the same order of magnitude. The within-farm diversity was not farm-specific but quantitatively high, i.e. up to 50% of the total genotypic diversity of a given village. Given the relative importance of the within-variety diversity, the in situ approach stands out as the most effective solution. As farms do not host specific diversity the in situ approach could be implemented by working with a small number of farms.     

Ecogeographic and genetic diversity based on morphological characters of indigenous rice (Oryza sativa L.) in Yunnan, China

Yunnan is one of the largest centres of genetic ecological diversity and the richest area for elite germplasm of rice (O. sativa L.) resources in the world. Its indigenous rice average diversity index of six ecological groups are, in turn, javanica (1.2319) > aman (1.1738) > communis (1.1726) > nuda (1.1618) > aus (1.1371) > boro (0.9889), and there are great differences between indica (1.1454) and japonica (1.2081). The indigenous rice in Yunnan can be divided into 58 varieties, almost the total number found in China, and the cultivars account for 8.6% of the total cultivars in China. A great difference in ecological diversity index of rice resources between prefectures or counties in Yunnan province also exists, with the southwest part (Lincang, Xishuangbanna, Dehong, Simao) and southeast part (Wenshan) having been found to be the largest centre of genetic diversity, as their average genetic diversity index ranges from 1.2735 to 1.2036, especially. The average diversity index of the Cangyuan, Gengma, Zhenkang, Yongde, Yingjiang, Jinghong, Menghai, Shuangjiang, Ruili, Longchuan, Mojiang, Wenshan and Guangnan counties, in particular, have an average diversity index ranging from 0.8 to1.0. On the contrary, in Diqing, Dongchuan, Kunming, Lijiang, Qujing, Chuxiong, it is comparatively low, i.e., 0.7843–1.1075. Differences in the ecological diversity index of rice resources between rice regions are small, only 1.1322 to 1.2849.     

杉木及其混交林的结构与功能模型——以福建省将乐国有林场为例

为提高森林多功能经营水平和森林效益,以福建省将乐国有林场内典型的杉木及其混交林为例,以17个易测因子为自变量,分别以森林生物量积累功能、水源涵养功能、保育土壤功能以及生物多样性保护功能为因变量,建立林分结构与功能的多元线性回归模型,并利用主成分分析法得到森林综合功能模型.结果表明:1)林分年龄、平均胸径和密度对森林的各项功能均具有一定的影响,林分平均高更侧重于影响森林的水源涵养功能.2)决定森林多功能水平的林分因子主要为林分年龄和林分平均胸径.3)在55块调查标准地中,森林综合功能指数最高为453,最低为-153.将乐国有林场82％的杉木林综合功能良好,18％的杉木林木材生产能力和多样性保护能力较弱,需针对这部分林分进行结构调整以提高森林的多功能性.     

Impacts of land fragmentation on input use,crop yield and production efficiency in the mountains of Nepal

Amidst the growing concern about agricultural underdevelopment in developing countries, this study addresses the causes and trends of land fragmentation. It analyses the impact of land fragmentation on input use efficiency, crop yield and production efficiency, especially with reference to a mountain district in Nepal. Necessary information was obtained from discussions with groups and individual land users and a questionnaire survey covering 184 households representing different degrees of land fragmentation. The analyses focused on two staple crops, namely, maize and paddy. The analysis revealed an increasing trend in the number of land parcels and a decreasing trend in the size of land parcels, primarily due to the heredity tradition of equal division of land among the inheritors. Other factors such as land purchase have also contributed to land fragmentation. Yield analysis revealed that small parcels are more productive than large parcels, because of higher applications of inputs. Consistent with this, small parcels also appeared to have a higher production efficiency than large parcels—considering both benefit and cost of purchased inputs—indicating a positive impact of land fragmentation on farmers' income. However, an analysis considering also the cost of inputs produced on the farm revealed an opposite trend, that is, on large land parcels, production is more efficient than on small parcels. In view of the need to also recover the cost of the inputs produced on‐farm, it is concluded that land fragmentation—leading to small plots—has a negative impact on production efficiency, thereby constraining agricultural development. Copyright © 2007 John Wiley & Sons, Ltd.     

Bats in a fragmented landscape: Species composition, diversity and habitat interactions in savannas of Santarém, Central Amazonia, Brazil

Species response to forest fragmentation may strongly vary according to ecological requirements, shape, spatial configuration and connectivity of fragments, and the structure of the surrounding matrix. Bats are natural candidates for studies on forest fragmentation. However, the conclusions of such studies are often contradictory. We present the results of a study on the effects of forest fragmentation on bat communities in Alter do Chão, Santarém area, in Central Amazonia, Brazil, an area composed by forests and fragments surrounded by savanna-like vegetation. We compared the species composition between habitats, tested the effect of size, shape and density of trees of forested areas on the presence species and their relative frequency of captures, and investigated the savannas as an ecological barrier for the dispersion of bats. With an effort of 5678 mistnet-hours, we captured 3740 bats (64 species). Multidimensional Scaling indicated no strong separation between the habitats sampled, however, savanna sites were grouped distinctly of fragments and forest sites. Multiple linear regressions indicated no significant correlation between the number of bat species recorded and the size, shape or tree density in forest sites and fragments. There was a significant correlation between the number of captures and the variables tested, explained by the shape of the sites, but not by size or tree density. In general, sites with bigger shape indices had fewer captures. Ten of the 20 most captured species showed no significant difference between the three habitats. The bat communities in Alter do Chão were not strongly affected by forest fragmentation, and the savannas did not appear to act as an ecological barrier to bats.     

区域景观中生境特异性对昆虫多样性的影响——以西双版纳为例

生境特异性(habitat-specific)在维持生物多样性上发挥着重要作用。本研究旨在了解在区域景观中,不同类型生境对不同类群昆虫多样性的贡献及群落结构差异,从大尺度上探讨昆虫多样性分布格局和维持机制。于2019年8—9月,在西双版纳地区利用样线调查法,调查了保护区、次生林、人工林和农田4种生境中蝴蝶、蝽和甲虫的物种数、特有物种数,分析了昆虫群落的生境特异性指数、群落结构相似性及物种丰富度与生态因子的关系。共采集昆虫2588头,其中蝴蝶94种(744头),蝽197种(1094头),甲虫129种(750头),保护区的昆虫物种数和特有物种数均高于其余类型生境。保护区昆虫群落的生境特异性指数实测值高于期望值,而其余类型生境昆虫群落的生境特异性指数实测值均低于期望值;不同类型生境间,3个类群的昆虫群落汇总的生境特异性指数不存在显著差异(F_(3,57)=2.054),甲虫生境特异性指数差异显著(F_(3,55)=3.478),蝴蝶(F_(3,38)=1.504)和蝽类(F_(3,53)=1.153)生境特异性指数差异不显著。群落结构相似性分析显示,保护区和农田的3个类群昆虫群落汇总的群落结构差异显著;次生林和人工林的蝴蝶群落结构差异显著,保护区和次生林的蝽类群落结构差异显著,甲虫昆虫群落结构差异不显著。本研究还发现,只有生境类型对昆虫群落的物种丰富度产生的影响极显著(P0.01),而其他生态因子的影响不显著。在大尺度区域景观中,保护区对昆虫群落的多样性影响最大,生境类型与昆虫群落的物种丰富度密切相关,保护较好的天然林是维持区域昆虫群落分布格局和多样性的重要机制。     

Local Organizations Involved in the Conservation of Crop Genetic Resources: Conditions for their Emergence and Success in Ethiopia and Kenya

Local organizations comprising of farmers, local formal and informal institutions, and public conservators can potentially be relevant options to confront the challenges of conserving indigenous crop varieties in developing countries. Although property rights and market failure problems experienced in crop genetic resources (CGRs) are different from other natural resources such as forests, wildlife, etc., such local organizations, and contractual arrangements within them, can be very instrumental in enhancing on-farm conservation. However, empirical investigations of such local organizations in order to determine the dimensions of their feasibility have been scarce. Against this background, this paper analyzes interactions of stakeholders in these local organizations and then explores the conditions for their emergence and success. The paper discusses field cases of on-farm conservation of traditional cereals and pulses from Ethiopia and indigenous vegetables from Kenya. It points out that local organizations conserving CGRs can be classified into different categories of contractual arrangements depending on certain driving factors that influence interactions of stakeholders and devolvement of decision-making authority. The paper further argues that these driving factors, which include accessibility to markets, presence of collective action or self-organizational capacity and provision of relevant CGRs conservation policies, form some of the key conditions determining the success of the case study organizations. The paper concludes by outlining policy implications on the structuring of such local organizations and the importance of certain factors in facilitating their emergence and success.     

Assessing landscapes: a case study of tree and shrub diversity in the seasonally dry tropical forests of Oaxaca, Mexico and southern Honduras

Tropical dry forests, with their distinct and economically important diversity, are acknowledged conservation priorities because of alarming rates of forest conversion. Whilst it is realised that terrestrial conservation requires an understanding of landscape level patterns of diversity, forests are rarely assessed accordingly. Here we demonstrate that, in the case of the seasonally dry tropical forests of the Pacific watershed of Mesoamerica, landscape level assessment of woody diversity can inform decision making relevant to both between-landscape and within-landscape prioritisation. We report floristic surveys of dry forest landscapes in Oaxaca, Mexico and southern Honduras. It is noted that these forests are floristically similar to other seasonally dry tropical forests in the neotropics. By calculation of Genetic Heat Indices, a relative measure of the concentration of restricted range species in a sample, we determine that the conservation of the tree diversity of the coastal lowlands of Oaxaca should be prioritised over that of southern Honduras. The current conservation status of forested areas in Oaxaca is briefly described. We suggest that the greater degree of anthropogenic disturbance in southern Honduras may explain the relative lack of restricted range species there. We argue that some forest fallows can act as analogues of mature forest and therefore landscape elements other than mature forest need to be included in forest conservation assessments. We conclude that diversity sampling of any forest type should not be limited to mature forests, but extended to other elements of forested landscapes.     

气候变化对杭嘉湖地区水稻生育期温度适宜性及生产潜力的影响

在田间试验和实地观测资料的基础上,确定了温度适宜性评价函数和生产潜力计算参数,分析了气候变化对杭嘉湖地区水稻生育期温度适宜性和生产潜力的影响。结果表明,由于气候变化,特别是温度条件的变化,使早稻移栽分蘖期和灌浆成熟期、晚稻抽穗开花期和灌浆成熟期的温度条件有很大改善,4个时期温度适宜性评价的平均值1981～1997年分别比1951～1980年提高了11.1%、5.2%、13.4%和13.2%。除早稻光温生产潜力明显增加外,早稻光能生产潜力和晚稻光能、光温生产潜力均呈下降趋势,但早稻和晚稻光温生产潜力及光能生产潜力比值均呈升高趋势,说明温度条件改善和补偿作用明显。     

Indigenous collaborative research for wildlife management in Amazonia: The case of the Kaxinawá, Acre, Brazil

Wildlife is a critical food resource throughout Amazonia. Consequently, adaptive management based on continued resource evaluation is essential to ensure long-term sustainable use of Amazonian wildlife. Since 1996, the Kaxinawá people of Western Amazonia have participated in a capacity-building program focused on natural resource management leading to the development of a territorial management plan that includes monitoring of wildlife use. In this study, we report the results of collaborative management-oriented research where hypotheses designed by the Kaxinawá about game availability within their territory were supported by the analysis of self-monitoring hunting data collected through a methodology designed in collaboration with conservation biologists. Results support Kaxinawá hypotheses that: (1) there is variation of game availability among villages in Kaxinawá territory; (2) preferred game species are more available to those villages closest to the isolated headwaters; and (3) previous land and wildlife use, present density of villages, and human population density are the main factors causing observed variations of game availability. The results of this study suggest the relevance and value of long-term participatory studies to complement short-terms academic studies of biodiversity and natural resource use and management.     

CO2浓度升高对水稻生物量及C、N吸收分配的影响

采用FACE(FreeAirCarbon-dioxideEnrichment)技术研究2种N水平下CO2浓度升高对水稻生物量及C、N吸收分配的影响结果表明,与对照相比,高CO2显著降低水稻生物量和C在叶的分配比例,增加其茎、穗和根的分配。高CO2使N在叶的分配降低,穗的分配增加;低N和常规N处理水稻抽穗期根的分配分别降低9.67%和13.1%,其他生育期则增加3.5%~26.6%;拔节期茎的分配分别增加7.03%和5.71%,成熟期分别降低10.5%和7.43%。N水平对水稻生物量和养分分配的影响不显著。     

Effect of insecticides on the availability of nutrients,nitrogen fixation,and phosphate solubility in the rhizosphere soil of rice

A field experiment was conducted to investigate the effects of 1,2,3,4,5,6-hexachlorocyclohexane (BHC), phorate, carbofuran, and fenvalerate, at their recommended doses, on some chemical and microbiological properties of the rhizosphere soil in relation to rice yields. In general, the insecticides had a beneficial effect on rhizosphere soil properties. Carbofuran strongly stimulated the mineralization of organic C. BHC and phorate led to the retention of less total N in the soil. BHC released more NH _inf4 ^sup+ -N than the other insecticides. Phorate, however, liberated the most NO _inf3 ^sup- -N. Phorate and fenvalerate released more available P than BHC and carbofuran did. All the insecticides stimulated the proliferation of aerobic non-symbiotic N₂-fixing and phosphate-solubilizing microorganisms, resulting in an overall increase in rice yield. BHC had the greatest effect on rice yields, followed by phorate.     

冬季秸秆还田对冬灌田水稻生长期CH4产生、氧化和排放的影响

有机肥施用和土壤水分管理是影响稻田CH4排放最重要的2个因素。本文通过室内培养和田间试验研究了冬季秸秆还田对冬灌田水稻生长期CH4的产生、氧化和排放的影响。结果表明:淹水混施处理CH4产生潜力在水稻移栽后35和51天显著大于淹水不施肥处理(p0.05),其余时间则无显著差异(p0.05);冬季秸秆还田对CH4氧化潜力无显著影响(p0.05),水稻生长期土温和稻田施用氮肥可能是较其更重要的影响因素;淹水混施处理CH4平均排放通量(CH426.7mg/(m2·h))显著大于淹水不施处理(CH420.3mg/(m2·h))(p0.05)。     

Population baseline data for monitoring genetic diversity loss for 2010: A case study for Brassica species in the UK

The Convention on Biological Diversity and the subsequent International Treaty on Plant Genetic Resources for Food and Agriculture have proved a watershed in plant genetic resources (PGR) conservation and consequent initiatives have set various PGR conservation targets to be met by 2010. The aim of our paper is to develop ideas and issues concerning the monitoring of natural genetic resources: particularly in terms of developing a baseline from which to measure levels of genetic diversity. Three species of Brassica (B. nigra, B. oleracea, B. rapa) found wild in the UK were assessed for levels of genetic diversity using AFLP. The relationship between genetic distribution and ecogeographic distribution was considered for each species to determine patterns that may be useful in formulating conservation strategies. Genetic distance between populations of B. nigra and B. rapa were correlated to geographic distance. Levels of genetic polymorphism in B. oleracea were correlated to soil pH while in B. rapa they were correlated to soil coarseness. In terms of PGR conservation these findings may suggest an emphasis toward in situ conservation of a selection of disparate populations would be appropriate where possible as such adaptations may be lost in ex situ collections.