Genetic variability in cultivated common bean beyond the two major gene pools

It is generally accepted that two major gene pools exist in cultivatedcommon bean (Phaseolus vulgaris L.), a MiddleAmerican and an Andean one. Some evidence, based on unique phaseolin morphotypesand AFLP analysis, suggests that at least one more gene pool exists incultivated common bean. To investigate this hypothesis, 1072 accessions from acommon bean core collection from the primary centres of origin, held at CIAT,were investigated. Various agronomic and morphological attributes (14categorical and 11 quantitative) were measured. Multivariate analyses,consisting of homogeneity analysis and clustering for categorical data,clustering and ordination techniques for quantitative data and nonlinearprincipal component analysis for mixed data, were undertaken. The results ofmost analyses supported the existence of the two major gene pools. However, theanalysis of categorical data of protein types showed an additional minor genepool. The minor gene pool is designated North Andean and includes phaseolintypes CH, S and T; lectin types 312, Pr, B and K; and mostly A5, A6 and A4 types-amylase inhibitor. Analysis of the combined categorical data ofprotein types and some plant categorical data also suggested that some othergermplasm with C type phaseolin are distinguished from the major gene pools.     

Crossing the thresholds: human ecology and historical patterns of landscape degradation

In discussions of landscape sensitivity, human activities have generally been regarded as external forces contributing to landscape change, with a focus on the impacts of cultivation methods, fertiliser practices, grazing pressures and atmospheric pollution. However, there has been comparatively little study undertaken that integrates physical and social systems in a historic context to explain the basis of human activity in sensitive landscapes. Where such attempts have been made, the manner of common land management has figured prominently, with ‘tragedy of the commons’ concepts used to explain land degradation and to provide a foundation for policy response. This has also been the case in Southern Iceland and in this paper we assess the extent to which common land domestic grazing pressures were the primary external force causing soil erosion and land degradation during the period of occupation from ca. 874 AD. We first provide field observation of soil erosion, temporally defined by tephrochronology, to highlight the extent of land degradation during this period. The ‘tragedy of the commons’ explanation of degradation is then assessed by evaluating historic documentary sources, and by environmental reconstruction and modeling of historic grazing pressures. These analyses indicate that regulatory mechanisms were in place to prevent overgrazing from at least the 1200s AD and suggest that there was sufficient biomass to support the numbers of domestic livestock indicated from historic sources. We suggest that failure to remove domestic livestock before the end of the growing season and an absence of shepherding were more likely to contribute to land degradation than absolute numbers. Lack of appropriate regulation of domestic livestock on common grazing areas can be attributed to limited cultural knowledge of changing and rapidly fluctuating environmental conditions.     

Field evaluation of N2 fixation and N partitioning in climbing bean (Phaseolus vulgaris L.) using 15N

Summary The common bean (Phaseolus vulgaris L.) is generally regarded as a poor N₂ fixer. This study assessed the sources of N (fertilizer, soil, and fixed N), N partitioning and mobilization, and soil N balance under field conditions in an indeterminate-type climbing bean (P. vulgaris L. cv. Cipro) at the vegetative, early pod-filling, and physiological maturity stages, using the A-value approach. This involved the application of 10 and 100 kg N ha^-1 of ¹⁵N-labelled ammonium sulphate to the climbing bean and a reference crop, maize (Zea mays L.). At the late pod-filling stage (75 days after planting) the climbing bean had accumulated 119 kg N ha^-1, 84% being derived from fixation, 16% from soil, and only 0.2% from the ¹⁵N fertilizer. N₂ fixation was generally high at all stages of plant growth, but the maximum fixation (74% of the total N₂ fixed) occurred during the interval between early (55 days after planting) and late podfilling. The N₂ fixed between 55 and 75 days after planting bas a major source (88%) of the N demand of the developing pod, and only about 11% was contributed from the soil. There was essentially no mobilization of N from the shoots or roots for pod development. The cultivation of common bean cultivars that maintain a high N₂-fixing capacity especially during pod filling, satisfying almost all the N needs of the developing pod and thus requiring little or no mobilization of N from the shoots for pod development, may lead to a net positive soil N balance.     

Soil conservation policy measures to control wind erosion in northwestern Europe

Wind erosion is not as significant or a widespread problem in Europe as in dryer parts of the world, but it can cause major damage in small areas. The hazard is greatest in the lowlands of northwestern Europe with more than 3 million ha at high-potential wind erosion risk. Crop damage and off-site damage have prompted farmers and policymakers to pay more attention to wind erosion control. A great variety of measures have been developed in the last decades. Most farmers, however, only use measures to protect their high value crops. In existing policies, little attention is paid to the off-site effects and long-term effects of wind erosion. There are no direct policy measures at a European level to control soil erosion, and few measures exist in individual Member States. Agricultural or environmental EC policies offer different policy tools to approach the wind erosion problems related to agricultural practices. Tools like subsidies for the re-afforestation of arable land can help regional policy makers with the implementation of wind erosion control measures. A case study concerning the ‘Code of Good Agricultural Practice’ shows that regional differences result in different control measures that fits best given the physical, social and economic context. The formulation of the practical details of such code should therefore remain a task of the local or regional government. The main objectives of a Code of Good Agricultural Practice could be formulated at national or European level.     

普通小麦品种小偃54中α/β-醇溶蛋白编码基因的克隆与序列分析

醇溶蛋白是小麦籽粒贮藏蛋白的重要组分,其组成与含量对小麦加工品质具有重要影响。本研究建立了利用PCR从普通小麦基因组BAC文库中筛选含有α/β-醇溶蛋白基因序列BAC克隆的方法,并获得9个不同的含有α/β-醇溶蛋白基因的BAC克隆。从其中鉴定出17个α/β-醇溶蛋白基因,其编码区序列长度为852~957 bp。12个序列在编码区内存在提前终止密码子,推测为假基因。其他5个成员(Gli-Xy54-1、Gli-Xy54-2、Gli-Xy54-3、Gli-Xy54-7和Gli-Xy54-13)分别编码291、310、311、287和317个氨基酸残基,都具有α/β-醇溶蛋白一级结构的典型特征。根据推导的氨基酸序列中乳糜泻病诱发因子的分布情况及多聚谷氨酰胺重复区的长度差异,推测Gli-Xy54-7可能定位于6A染色体,Gli-Xy54-2、Gli-Xy54-3和Gli-Xy54-13可能定位于6B染色体,Gli-Xy54-1可能定位于6D染色体。基因聚类分析支持了上述推论。这是第一次从普通小麦中筛选到包含α/β-醇溶蛋白基因的BAC克隆,并从中得到目标基因全长,对进一步研究普通小麦基因组中α/β-醇溶蛋白编码基因的组成、表达与功能有较好的参考价值。     

小麦ERF转录因子W17互作蛋白的筛选和解析

来自小麦的ERF转录因子W17基因参与胁迫应答,过表达W17可显著提高转基因拟南芥的抗旱性和抗病性。本研究构建了小麦cDNA文库,通过酵母双杂技术筛选W17的互作蛋白,以期进一步解析ERF蛋白的作用机制。将pGBKT7-W17质粒、pGADT7和小麦文库混合转入酵母细胞AH109,在SD/–Trp/–Leu/–His/–Ade营养缺陷型平板上培养,挑选直径大于2 mm的克隆,在SD/Raf/Gal/X-gal平板上划线培养,筛选蓝色克隆。将筛出的克隆测序、BLAST分析,得到4类与W17相互作用的候选蛋白,分别是胁迫相关功能蛋白、翻译后修饰蛋白、1,5-二磷酸核酮糖羧化酶/加氧酶(Rubisco)大亚基/小亚基以及功能未知蛋白。互作验证表明,Hsp90和PPR蛋白与W17有相互作用关系。这些候选蛋白参与信号转导或免疫过程,暗示W17在植物的逆境信号转导、下游基因转录调控,甚至在翻译过程都有重要作用。     

欧盟的粮食安全政策及对我国的启示

分析探讨了欧盟国家对粮食安全的认识,介绍和分析了欧盟国家在粮食安全问题上的政策和措施,通过与我国农业发展现状的比较,揭示了欧盟食物安全政策对我国粮食安全和现代化农业建设所具有的重要启示作用,提出了加强粮食安全和农业发展的建议和措施.建立符合中国国情的粮食预警体系;实施农业保护政策,提高农业综合生产能力;深化粮食流通体制改革,建立安全可靠的粮食储备系统;建立食物安全生产的诱导机制;生态建设要与粮食生产能力建设和储备相结合.     

小麦中国春背景下长穗偃麦草光合作用相关基因的染色体定位

 光合作用与小麦产量关系的研究倍受国内外学者关注，而以代换系为材料研究外源染色体对光合作用的效应至今未见报道。本文以小麦－长穗偃麦草二体代换系为材料，以旗叶为主要测定叶位，用美国CID公司生产的CI-310便携式光合作用测定系统于田间测定旗叶光合速率在各生育期变化，并测定其与产量构成因素间的相关性。结果表明，DS2Ee(2A)代换系在开花期具有在整个生育期最高的光合速率，2Ee染色体可在穗粒数性状的改良过程中加以利用。DS4Ee(4A、4B、4D)代换系其旗叶从抽穗期到灌浆期始终保持较高水平净光合速率，对籽粒形成和充实十分有利，4Ee染色体可在通过改良灌浆时光合速率来提高千粒重等产量指标的研究中加以利用。     

Isolation and Characterization of the Wheat cDNA Fragments Involved in salt Stress

cDNA-AFLP(amplified fragment length polymorphism) is used to isolate genes differentially expressed in salt-stressed and unstressed wheat lines RH8706-49 and H8706-34 derived from a single seed,representing a salt-stress resistant (SR) and salt-stress sensitive(SS) line,respectively.About 88.1% cDNA fragment are expressed in all the four samples,11.9% are different between the samples.68 cDNA fragments were cloned,of which 35 were subject to sequence analysis.Database searches indicate that 11 cDNA fragment show high homology to known genes,which mainly include proteins related to ion transport,signal transduction and oxidative stress.The remaining 24 cDNA show no detectable homology to known genes,suggesting that they probably represent novel genes.     

几种化感物质对大巢菜种子萌发及幼苗生长的影响

试验研究了酚酸类化感物质(阿魏酸、香草酸、丁香酸和对羟基苯甲酸)对麦田杂草大巢菜种子萌发及幼苗生长的影响,结果表明:阿魏酸、香草酸、丁香酸、对羟基苯甲酸能够延缓大巢菜种子的萌发,抑制大巢菜种子的萌发率、出苗率以及幼苗的生长,并且随着浓度的增加抑制作用加强;四种酚酸类化感物质的抑制效果表现为香草酸>丁香酸>对羟基苯甲酸>阿魏酸。