Allelopathy and Its Implications in Agroecosystems

Summary

Allelopathy includes both positive and negative effects of one plant on the other through environment, though most of the studies seem to focus on its deleterious impacts. It plays a key role in both natural and managed ecosystems. In agroecosystems, several weeds, crops, agroforestry trees and fruit trees have been shown to exert allelopathic influence on the crops, thus, affecting their germination and growth adversely. Some of the agricultural and horticultural crops affect their own seedlings grown in succession which is commonly known as replant problem/syndrome. Available studies indicate that allelochemicals act via bringing certain changes in physiological functions like respiration, photosynthesis and ion uptake. These, in turn, result in visible changes in seed germination, further growth reduction and overall performance of the target plants. The studies on interplant interactions assume significance in agroforestry programmes for selecting the types of crops complementary to the selective tree species. In the recent past, however, scientific attention has also been drawn to exploit the positive significant roles this phenomenon can play in enhancing crop productivity. In this context, we discuss the tremendous scope of allelopathy towards weed and pest management, apart from nitrogen conservation, and synthesis of novel agrochemicals based on natural product chemistry. The use of natural products of plant or microbial origin as pesticides/herbicides have gained much attention of the scientists as they offer many advantages over synthetic chemicals. The production of such chemicals should be enhanced by devising suitable protocols based on biotechnological procedures for their widespread utilization.     

Research Priorities in Natural Systems Agriculture

SUMMARY

Over the course of millennia and most dramatically in recent years, agriculture has eroded natural capital as it has supplied human demands. These tendencies can be offset by infusions of fossil fuels for fertility, pest control and traction, but only partially and not over the long term. This could be called the “problem of agriculture,” in contrast to problems in agriculture. Natural ecosystems are unmatched for efficient nutrient recycling, solar energy use, and biodiversity preservation, but they cannot feed dense human populations. An ecological agriculture that is a synthesis of natural and agricultural systems can save soils from erosion and reduce chemical and water use. Reducing chemical pollution of air, water and soils will conserve wildlife habitat, improve water quantity and quality and protect human health. By practicing an agriculture that has conservation as a direct result, farmers can become better stewards of the land. Lower input costs and inherent sustained soil fertility will mean more profit for farmers and communities. Principles of natural systems agriculture (NSA) are applicable to any food- or fiber-production system worldwide. In the central Great Plains of the United States, agriculture should mimic the native prairie, which is a polyculture of herbaceous perennial plants. The Land Institute has spent 25 years studying the structure and function of prairies. Now we and other research organizations are breeding perennial grain crops, including cool- and warm-season grasses, legumes, and composites. We are following two parallel strategies: selecting wild perennials for greater seed production and other traits of domestication and hybridizing wild perennials with annual crops to combine desired traits. Although the breeding process will take many years, the effort will be repaid many times over if we achieve our goal: a lasting solution to the 10,000-year-old problem of agriculture.     

Education in Agroecology and Integrated Systems

Summary

Courses and curricula in agriculture are traditionally organized within disciplinary boundaries, while study of integrated systems has been confined to aggregation of components and often superficial analysis. Agroecology is emerging as an integrative field that expands our focus to embrace the broad complexities of agricultural production and the entire food system. Education in agroecology must provide the skills and knowledge needed to design and evaluate new systems, as well as the capacity to vision into the future and anticipate the impacts of systems as well as new challenges that will face humanity. Agricultural universities need to be organized to prepare students to meet these increasingly complex challenges in the food and natural resource arena. Agroecology courses can build awareness and competence in using ecological principles to inform the design of future systems that are productive, economically sound, environmentally sustainable, and socially viable for the indefinite future. A model program in the Nordic region is presented as an example of one innovative curriculum. Study of the ecology of food systems can put natural resource, human population, and agricultural production into a balanced perspective that can guide our research and development efforts toward a sustainable food system for the future.     

Genetic Diversity of Wild Rice Species in Yunnan Province of China

Yunnan Province of China is one of the important centers for origin and evolution of cultivated rice worldwide.Wild rice is the ancestor of the cultivated rice.Many elite traits of wild rice have widened the genetic basis in cultivated rice.However,many populations of wild rice species have disappeared in the past few years.Therefore,the current status of wild rice resources should be updated and the genetic diversity of wild rice species should be examined for further germplasm preservation and utilization.Our investigations showed that the number of natural wild rice populations declined sharply in Yunnan Province during the past few years due to various reasons.Fortunately,one population of Oryza rufipogon,three of O.officinalis and ten of O.granulata have been newly found in different ecological sites,which were confirmed by inter-simple sequence repeat(ISSR) marker analysis in this study.ISSR analysis and investigation of some important traits of nutritional values indicated that the genetic diversity of the currently existing wild rice resources in Yunnan is still rich.The demonstration of genetic diversity of wild rice by a combined use of geographical distribution,morphological traits,nutrition contents and ISSR markers would be helpful for the conservation and exploration of these important wild rice resources.     

482份红花种质资源农艺性状的遗传多样性分析

为筛选药食两用的优质红花种质,对来源于30个国家和地区的482份代表性红花种质进行评价.基于大田试验,在红花成熟期时选择株高、分枝高度、顶端分枝高度、一级分枝数、二级分枝数、幼苗存活率、开花期、花色、叶片有/无刺、苞叶有/无刺、叶缘、千粒重12个农艺性状,采用遗传多样性、相关性、主成分分析和聚类分析的统计方法,综合评价...     

Effects of Key Soil Organisms on Nutrient Dynamics in Temperate Agroecosystems

Summary

Soil organisms are a diverse group that can influence the nutrient dynamics in temperate agroecosystems profoundly. Many organisms interact in a symbiotic or mutualistic way with plants, and these relationships have co-evolved, permitting plants and soil organisms to flourish in the soil environment. Numerous controlled lab or small plot-scale studies have demonstrated that soil organisms can mobilize or transfer substantial quantities of nutrients to crops, in relationship to crop requirements. However, the simple scaling up of such results to explain conditions on a large field scale is very much constrained by a lack of information on the spatio-temporal distribution of soil organisms in temperate agroecosystems. The numbers, diversity and activity of soil organisms in temperate agroecosystems are affected by agricultural management practices such as tillage operations, but our knowledge of the key organisms or groups of organisms that contribute to nutrient cycling and crop production under different sets of management practices is limited. Better management of nutrients in temperate agroecosystems requires better knowledge of soil biota, their effects on nutrient cycling and their contribution to crop production.     

我国红麻种质资源的遗传多样性与评价利用

我国是世界上最大的红麻生产国，也是最大的种质资源拥有国。我国政府十分重视红麻种质资源的研究和利用，并促进其在育种和生产中的利用。本文讨论了我国红麻的种植历史、种质资源的遗传多样性及收集保存、鉴定评价、利用创新等问题。同时还探讨了红麻遗传多样性研究中的问题，提出了持续发展和利用对策。我国红麻种质资源研究和利用的成功经验，可为红麻产业的持续发展提供有益的借鉴。     

24份西番莲种质SSR分子标记分析

采用SSR标记对24份西番莲材料的遗传多样性进行研究,从45对引物组合中筛选出16对扩增带清晰、重复性好的引物组合。结果表明：16对SSR引物共产生68条扩增带,其中58条为多态性条带,多态性条带比率平均为85.3 %,24份材料的遗传相似系数(GS)的范围为0.09-1.0;UPGMA法聚类分析结果表明,24份西番莲种质以0.45为阈值可分为7大类,SSR标记丰富的多态性可在西番莲分子生物学领域中广泛应用。     

利用SSR分析普通野生稻自然居群交配系统

采用SSR标记技术检测了6个自然居群的遗传多样性和交配系统参数,旨在了解其居群交配系统,为有效原位保护、异位保存提供指导。结果表明,6个居群遗传多样性水平存在差异(基因多样性指数变幅为0.3166～0.6075),居群间分化明显(Fst=0.4220)。广东高州大岭居群和广东高州朋山居群有过剩的杂合子(F0),而另外4个居群有过剩的纯合体(F0)。普通野生稻6个取样居群交配系统为混合交配类型,居群之间的异交率相差较大(多位点异交率变幅为15.1%～41.8%,单位点异交率变幅为10.1%～28.5%)。6个居群的多位点异交率都高于单位点异交率,而且位点亲本相关度比较大,说明居群内存在一定程度的近交。同时,各居群单位点相关度与多位点相关度差值较大,表明居群内存在亚结构。还讨论了进一步改善普通野生稻原位和异位保护的措施。     

中国普通野生稻的原地保护及其遗传多样性研究进展

普通野生稻是亚洲栽培稻的祖先种,是重要的稻种资源。介绍了中国普通野生稻的分布和原地保护现状,综述了中国普通野生稻的遗传多样性评价和交配系统研究进展。     

77份文心兰种质资源表型性状遗传多样性分析

对文心兰77份种质资源的28个表型性状进行测定与评价,通过相关性分析、主成分分析及聚类分析获得其表型遗传多样性.结果表明:21个数量性状的遗传多样性指数均值达1.85,变化区间为1.36～2.07,其中数值最大为株幅(2.07);在7个质量形状中,除叶色性状外的其他表型性状的多样性指数均大于1,均值为1.23,最大表现...     

保护性耕作技术在中国农业生产中的意义

针对我国农业生产中存在的一些问题,提出了相应的保护性耕作技术和合理的解决措施,同时也指出了目前我国保护性耕作技术体系中的各别弊端.通过对利弊两方面的阐述分析了我国农业生产可持续发展的方向.     

麻类种质资源遗传多样性评价研究进展

对麻类种质资源遗传多样性的评价,是对麻类资源全面系统理论研究的基础和前提。本文从形态学标记、细胞学标记、同工酶标记和DNA分子标记技术四个方面综述了麻类种质资源遗传多样性评价研究进展,为麻类种质资源评价的研究提供理论依据。     

麻类种质资源遗传多样性评价研究进展

对麻类种质资源遗传多样性的评价,是对麻类资源全面系统理论研究的基础和前提.本文从形态学标记、细胞学标记、同工酶标记和DNA分子标记技术四个方面综述了麻类种质资源遗传多样性评价研究进展,为麻类种质资源评价的研究提供理论依据.     

益智种质资源表型性状的遗传多样性分析

对收集的90份益智种质资源的18个表型性状进行遗传多样性分析,以期为益智品种改良和种质创新提供依据.结果 表明:供试的益智种质具有丰富的遗传多样性,质量性状中多样性指数最高的为果形(1.1507),数量性状中多样性指数最高的为株高(2.0700),变异系数最大的为结果枝数(41.32％);提取的6个主成分累计贡献率为6...     

中国热带草业产业化开发经验与可持续发展模式探讨

总结我国热带草地资源开发利用经验，探讨我国热带草业产业化可持续发展模式，提出：中国热带草业的产业化开发不应局限于本行业，还要和热带农业的持续发展结合起来，要和当时当地农民土地经营状况、生产水平和社会文化状况结合起来，要把增加农民收入作为基本要求，不断提高经济效益、生态效益和社会效益。认为实现热带草业产业化应朝以下8个方向努力：①逐步建立以适度规模经营为主的庭院经济生产模式；②要应对市场，特别是满足城市的需求；③应尽可能和热带优势产业的发展结合；④努力围绕创立和培养品牌；⑤逐步建立起标准化生产模式；⑥坚持农业基础设施的建设和逐步实现机械化；⑦坚持新技术的应用和普及；⑧努力争取国家、企业、科教单位、个人及先进国家智力、财力的支持。     

The Challenge of Ecophysiological Biodiversity for Biotechnological Applications of Marine Microalgae

In this review, we aim to explore the potential of microalgal biodiversity and ecology for biotechnological use. A deeper exploration of the biodiversity richness and ecophysiological properties of microalgae is crucial for enhancing their use for applicative purposes. After describing the actual biotechnological use of microalgae, we consider the multiple faces of taxonomical, morphological, functional and ecophysiological biodiversity of these organisms, and investigate how these properties could better serve the biotechnological field. Lastly, we propose new approaches to enhancing microalgal growth, photosynthesis, and synthesis of valuable products used in biotechnological fields, mainly focusing on culture conditions, especially light manipulations and genetic modifications.     

云南古茶树(园)遗传多样性的ISSR分析

云南省保存有20多万亩古茶园,这些古茶树（阿萨姆变种Camellia sinensis var. assamica）种质资源可能含有各种优良基因,对未来茶树良种选育有重要意义。本研究采用ISSR分子标记技术对云南省十个有代表性的古茶园遗传多样性进行分析,十个居群的多态位点百分率（P）为56.5%~90.9%;Nei’氏遗传距离（He）居群平均是0.281,阿萨姆变种水平内是0.461;Shannon多样性指数(Ho)居群平均是0.418,阿萨姆变种水平内是0.653。而居群间遗传分化系数Gst=0.391,和Shannon多样性指数分析（36.0%）和AMOVA分析结果（39.7%）相一致,说明阿萨姆变种60.9%的遗传变异来自居群內的个体间,39.1%的遗传变异来自居群间。研究结果揭示阿萨姆变种居群遗传多样性高,居群间遗传变异存在中度的遗传分化,这可能是由于茶树种内高度异交的特性和生境片段化所致。基于观察到的居群遗传信息,建议采取就地保护和迁地保护的保护策略。     

甘蔗种质资源遗传多样性及杂交利用研究进展

从种质资源搜集保存、细胞遗传学、分子遗传学、杂交利用方面详细论述了甘蔗种质资源的研究进展情况并进行了深入分析和讨论,提出了种质资源研究存在的问题和今后的研究方向。     

稻田生态种养在日本的发展及其对中国生态农业的启示

日本的生态农业已经取得较大的发展成效.稻鱼共生是中国的传统农业文明,现已发展出稻鸭、稻虾、稻鳖等多种生态种养模式,是中国生态农业发展的关键手段.日本与中国在地理位置、人口条件、农业文明上有许多共同之处,日本稻田生态种养结合生态农业的发展经验对今后中国的生态农业前进方向具有借鉴意义.