Domestication and the distribution of genetic variation in wild and cultivated populations of the Mesoamerican fruit tree Spondias purpurea L. (Anacardiaceae)

Domestication occurs as humans select and cultivate wild plants in agricultural habitats. The amount and structure of variation in contemporary cultivated populations has been shaped, in part, by how genetic material was transferred from one cultivated generation to the next. In some cultivated tree species, domestication involved a shift from sexually reproducing wild populations to vegetatively propagated cultivated populations; however, little is known about how domestication has impacted variation in these species. We employed AFLP data to explore the amount, structure, and distribution of variation in clonally propagated domesticated populations and sexually reproducing wild populations of the Neotropical fruit tree, Spondias purpurea (Anacardiaceae). Cultivated populations from three different agricultural habitats were included: living fences, backyards, and orchards. AFLP data were analysed using measures of genetic diversity (% polymorphic loci, Shannon's diversity index, Nei's gene diversity, panmictic heterozygosity), population structure (F(ST) analogues), and principal components analyses. Levels of genetic variation in cultivated S. purpurea populations are significantly less than variation found in wild populations, although the amount of diversity varies in different agricultural habitats. Cultivated populations have a greater proportion of their genetic variability distributed among populations than wild populations. The genetic structure of backyard populations resembles that of wild populations, but living fence and orchard populations have 1/3 more variability distributed among populations, most likely a reflection of relative levels of vegetative reproduction. Finally, these results suggest that S. purpurea was domesticated in two distinct regions within Mesoamerica.     

Biodiversity, evolution and adaptation of cultivated crops

The human diet depends on very few crops. Current diversity in these crops is the result of a long interaction between farmers and cultivated plants, and their environment. Man largely shaped crop biodiversity from the domestication period 12,000 B.P. to the development of improved varieties during the last century. We illustrate this process through a detailed analysis of the domestication and early diffusion of maize. In smallholder agricultural systems, farmers still have a major impact on crop diversity today. We review several examples of the major impact of man on current diversity. Finally, biodiversity is considered to be an asset for adaptation to current environmental changes. We describe the evolution of pearl millet in West Africa, where average rainfall has decreased over the last forty years. Diversity in cultivated varieties has certainly helped this crop to adapt to climate variation.     

中国西南纵向岭谷区外来入侵植物对生物多样性的影响

论述中国西南纵向岭谷区外来入侵植物对生物多样性的影响。中国西南纵向岭谷区是我国生物多样性保护的关键地区。目前,该区域已成为外来植物入侵的重灾区,外来入侵植物种类多达70余种,其中,紫茎泽兰Ageratina adenophora（Eupatoriumadenophorum）、飞机草Chromolaena odorata（Eupatorium odoratum）和肿柄菊Tithonia diversifolia等在该区域危害严重,该区域的生态系统的结构与功能遭受破坏,本地物种面临灭绝,农、林、牧生产乃至区域的生态安全受到威胁。该区域的外来入侵植物的危害居全国之冠。研究该区域的外来入侵植物,揭示其危害规律,遏制其危害速度,最终清除该区域的外来入侵植物,恢复该区域的生态平衡,具有十分重要的现实意义和科学价值。文中详细论述了外来入侵植物对植物物种多样性、植物群落多样性、生态系统多样性、农牧业及林业的影响,最后指出消除和控制外来入侵植物的途径。     

利用农业生物多样性持续控制有害生物

农业生物多样性对保障全球粮食安全和农业可持续发展至关重要.人类在多样性的形成上发挥了关键作用,人类结合自然进化创造了遗传多样性、物种多样性和生态系统多样性.农业生物多样性发挥了很多社会经济和环境功能:保障粮食安全;维持农业生态系统可持续发展;赋予农村经济适变性.但当前人类毁灭农业生物多样性的速度更为惊人.在总结石油农业单一化种植的生态负效应、传统农业提倡“天人合一”的生态正效应的基础上,分析讨论了利用农业生物多样性持续控制有害生物的必要性和可行性,从生态系统多样性、物种多样性和种内遗传多样性3个层次,归纳了构建和恢复农田生物多样性的基本方法.基于病理学、生态学、营养学和生理学等学科领域,从群体异质效应、稀释效应、微生态效应、诱导抗性效应、物理阻隔效应、生理学效应和化感效应等7个方面,归纳了利用农业生物多样性持续控制有害生物的基础原理.寻求低投入、高效益、多样化和可持续的农业生产系统是当今世界许多科学家、决策者和生产者共同关心的问题.农业生物多样性具有重要的生态作用,在现代农业框架下,是合情合理构建持续、稳定、健康、高产的农田生态系统,持续控制有害生物的金钥匙.为此必须加强四方面的课题研究:各种作物之间的相生相克关系及其作用机理;各种有害生物的主要天敌种类、生物学、生态学特性及其适生环境;利用农业生物多样性全面、持续控制有害生物的农业生产模式;与其相配套的农艺措施与农业机械.     

农业生态系统中的AM真菌多样性

农业生态系统复杂庞大,是由如麦田生态系统、水稻田生态系统、果园生态系统、草地生态系统、保护地生态系统等组成的一个复合生态系统。重点介绍农业生态系统中丛枝菌根(AM)和AM真菌多样性,探讨农业生态系统中调控AM真菌多样性的途径以及今后研究的动向。     

Vavilov's concept of centres of origin of cultivated plants: its genesis and its influence on the study of agricultural origins

N. I. Vavilov first published his concept of centres of origin of cultivated plants in 1926. For over fifty years it profoundly influenced thinking about the origins and spread of agriculture by bitanists, geograhers, anthropologists and archaeologists. The genesis of the concept and its exposition by Vavilov is examined, and its influence on the ideas of such scholars as C. O. Sauer, I. H. Burkill, C. D. Darlington, A. I. Kuptsov, R. Porteres, J. R. Harlan and J. G. Hawkes is traced. It is concluded that Vavilov's concept, which for so long conditioned ideas about the origins of agriculature, has now outlived its usefulness in thet field sof study.     

Domestication of cereal crops in the old world: in search of a new approach to solving old problem

N.I. Vavilov's theory of the centres of origin of cultivated plants is still as a methodological base for studying processes of domestication. This theory, along with archaeological, botanical, and molecular genetic data, helped to determine the most probable regions where the principal cultivated species were introduced into culture. The search for the mechanisms of origins of morphological changes in the course of domestication is one of evolutionary biology's oldest problems. Employing novd molecular biological data for solving this problem provides a key to the understanding of these mechanisms and helps to reconstruct a possible scenario of how the traits that distinguish domesticated plants from their wild relatives got involved into selection. It is hypothesized that distinct physiological and morphological differences important to ancient agrarians originated from quantitative and/or qualitative changes in the loci regulating the programmes of plant ontogeny. This hypothesis helps to reveal the mechanisms of origin of certain traits in the course of domestication, to study the connection between the direction of selection and how such traits are genetically controlled, and to outline particular ways for further detailed studies of the evolutionary aspect of domestication processes.     

Culturally valuable minority crops provide a succession of floral resources for flower visitors in traditional orchard gardens

Agricultural intensification typically has detrimental effects on pollinator communities, but diverse cropping systems that contain sequentially-flowering crops have the potential to benefit pollinators through the provision of additional floral resources. In this study we investigate the importance of cultivated flora for flower visitors in ten agricultural gardens in South Sinai, Egypt. Insect-flower interactions in gardens and unmanaged plots were surveyed across a four-month period in two environmentally distinct years (pre-flood and post-flood). Despite containing an equal abundance and diversity of wild plants as unmanaged habitat, gardens supported a higher abundance and diversity of flower visitors due to the additional presence of cultivated flora. Visitation networks exhibited dramatic intra-annual changes in composition, with cultivated plants becoming increasingly important in later months. Trends were highly conserved across 2 years despite highly contrasting rainfall. Several key crop species were strongly involved in shaping the structure of the networks, the majority of which were herbs with strong cultural significance (fennel, rosemary, mint) and grown incidentally alongside the primary orchard crops. Minority crops are frequently overlooked in agricultural systems due to their low economic value, but we show that they can have a dramatic influence upon the structure of visitation networks, increasing both pollinator abundance and diversity, and emphasising the link between cultural practices and biodiversity conservation.     

Plant–rhizobacteria interactions alleviate abiotic stress conditions

Root-colonizing non-pathogenic bacteria can increase plant resistance to biotic and abiotic stress factors. Bacterial inoculates have been applied as biofertilizers and can increase the effectiveness of phytoremediation. Inoculating plants with non-pathogenic bacteria can provide 'bioprotection' against biotic stresses, and some root-colonizing bacteria increase tolerance against abiotic stresses such as drought, salinity and metal toxicity. Systematic identification of bacterial strains providing cross-protection against multiple stressors would be highly valuable for agricultural production in changing environmental conditions. For bacterial cross-protection to be an effective tool, a better understanding of the underlying morphological, physiological and molecular mechanisms of bacterially mediated stress tolerance, and the phenomenon of cross-protection is critical. Beneficial bacteria-mediated plant gene expression studies under non-stress conditions or during pathogenic rhizobacteria–plant interactions are plentiful, but only few molecular studies on beneficial interactions under abiotic stress situations have been reported. Thus, here we attempt an overview of current knowledge on physiological impacts and modes of action of bacterial mitigation of abiotic stress symptoms in plants. Where available, molecular data will be provided to support physiological or morphological observations. We indicate further research avenues to enable better use of cross-protection capacities of root-colonizing non-pathogenic bacteria in agricultural production systems affected by a changing climate.     

Traditional agricultural gardens conserve wild plants and functional richness in arid South Sinai

Maintaining agricultural diversity is important for the conservation of rare species and for preserving underlying ecosystem processes on which smallholder farmers rely. The positive effects of crop diversity are well documented in tropical systems, but the conservation potential of arid agricultural systems is less clear. This study assesses the impact of three arid agroforestry systems on plant diversity and functional richness in South Sinai, Egypt: (1) mountain orchard gardens, (2) modern town gardens and (3) low desert date-palm gardens. We surveyed plants (cultivated and wild) within gardens and control plots of natural habitat and allocated each plant eight biological traits that are recognised as being linked with major ecosystem processes. Species diversity was quantified using three measures (Hill's numbers) and total species diversity was significantly higher within gardens than in the surrounding habitat at all three levels of diversity and across the three agroforestry systems. Species similarity was high between gardens and the surrounding habitat, and there was a strong overlap in the functional traits of wild plants and cultivated non-tree species. Despite the clear presence of trees within the gardens, the community weighted trait means (CWMs) showed that chamaephyte perennials were the dominant life-forms in both the gardens and the natural habitat. Functional richness differed between the three agroforestry systems, but was significantly higher within the gardens. Functional richness has been linked to increased productivity and CWMs showed that plants within the gardens were considerably taller than outside, suggesting higher biomass accumulation. These findings suggest that Bedouin agricultural practices are not having a negative effect on the flora of the region and that the continuation of these indigenous farming practices can actively benefit rare wild plants in the region. On a wider scale, this study supports the view that smallholder farms and homegardens can be valuable tools in conservation, preserving local species and maintaining ecosystem functioning.     

Characterizing Rural Household Differentiation from the Perspective of Farmland Transfer in Eastern China Using an Agent Based Model

Over the past several decades in China there has been a large amount of rural labor flow to non-farm industries as well as an increase in farmland transfers that have resulted in significant differentiation of farmer households and changes in agricultural land use pattern. For this study we developed an agent-based model to explore this process and the resulting concentration of agricultural production by characterizing the households’ decision-making behavior with respect to farmland transfer in Jinze Town, located in the developed eastern region in China. The model simulated the household agents’ farmland transfer behavior, reproduced the evolution and differentiation of household agents, and explored changes of farm area distribution across household types from 2005 to 2020. Small households, the dominant demographic as well the main agricultural producers at the beginning of the simulation, decreased radically and cultivated the smallest area of farmland by the end. In contrast, large-scale farming households increased rapidly and became the main agricultural producers. The majority of households entirely exited farming in favor of urban employment. We examine how farm households’ attributes influence their farmland transfer behavior and subsequent livelihood choices in the specific socioeconomic and political context in the research region. We conclude with policy suggestions for the provision of a favorable environment for both large-scale farm households and those who leave farming altogether. Our findings can provide references for land use policies in other transitional rural areas.     

Roles of instrumented farm-scale trials in trade-off assessments of pasture-based ruminant production systems

For livestock production systems to play a positive role in global food security, the balance between their benefits and disbenefits to society must be appropriately managed. Based on the evidence provided by field-scale randomised controlled trials around the world, this debate has traditionally centred on the concept of economic-environmental trade-offs, of which existence is theoretically assured when resource allocation is perfect on the farm. Recent research conducted on commercial farms indicates, however, that the economic-environmental nexus is not nearly as straightforward in the real world, with environmental performances of enterprises often positively correlated with their economic profitability. Using high-resolution primary data from the North Wyke Farm Platform, an intensively instrumented farm-scale ruminant research facility located in southwest United Kingdom, this paper proposes a novel, information-driven approach to carry out comprehensive assessments of economic-environmental trade-offs inherent within pasture-based cattle and sheep production systems. The results of a data-mining exercise suggest that a potentially systematic interaction exists between ‘soil health’, ecological surroundings and livestock grazing, whereby a higher level of soil organic carbon (SOC) stock is associated with a better animal performance and less nutrient losses into watercourses, and a higher stocking density with greater botanical diversity and elevated SOC. We contend that a combination of farming system-wide trials and environmental instrumentation provides an ideal setting for enrolling scientifically sound and biologically informative metrics for agricultural sustainability, through which agricultural producers could obtain guidance to manage soils, water, pasture and livestock in an economically and environmentally acceptable manner. Priority areas for future farm-scale research to ensure long-term sustainability are also discussed.     

Endophytic actinobacteria of medicinal plants: diversity and bioactivity

Endophytes are the microorganisms that exist inside the plant tissues without having any negative impact on the host plant. Medicinal plants constitute the huge diversity of endophytic actinobacteria of economical importance. These microbes have huge potential to synthesis of numerous novel compounds that can be exploited in pharmaceutical, agricultural and other industries. It is of prime importance to focus the present research on practical utilization of this microbial group in order to find out the solutions to the problems related to health, environment and agriculture. An extensive characterization of diverse population of endophytic actinobacteria associated with medicinal plants can provide a greater insight into the plant-endophyte interactions and evolution of mutualism. In the present review, we have discussed the diversity of endophytic actinobacteria of from medicinal plants their multiple bioactivities.     

Commercial production of microalgae in the Asia-Pacific rim

There are around 110 commercial producers of microalgae in the Asia-Pacific region, with annual production capacity ranging from 3 to 500 T. About nine-tenth of the algal cultivation plants are located in Asia. The commercially cultivated microalgae include Chlorella, Spirulina, Dunaliella, Nannochloris, Nitzschia, Crypthecodinium, Schizochytrium, Tetraselmis, Skeletonema, Isochrysisand Chaetoceros. Most of the commercially produced algal biomass is being marketed as health food, in the forms of tablets and capsules. Algae and their extract are also included in noodles, wine, beverages, breakfast cereals and cosmetics. This revised version was published online in August 2006 with corrections to the Cover Date.     

Genetic consequences of pre-Columbian cultivation for Agave murpheyi and A. delamateri (Agavaceae)

Pre-Columbian farmers cultivated several species of agave in central Arizona from ca. A.D. 600-1350. Because of the longevity and primarily asexual reproduction of these species, relict agave clones remain in the landscape and provide insights into pre-Columbian agricultural practices. We analyzed variation in allozyme allele frequencies to infer genetic effects of prehistoric cultivation on Agave murpheyi and A. delamateri, specifically to estimate genetic diversity and structure, to determine whether cultivated populations descended from a single clone, and to examine regional-scale genetic variation. Agave murpheyi maintained more genetic diversity at the species and population levels than A. delamateri, and A. murpheyi populations typically included more multilocus genotypes. Relict plants from prehistoric fields reflect a more complex history than descent from a single clone; A. murpheyi populations may have included more diversity initially because bulbils (produced routinely in A. murpheyi but not A. delamateri) and possibly seed would have facilitated transport of genetically diverse planting stock. Genetic variation in both cultigens was lower than in most contemporary commercial crops but similar to that observed in modern traditional agricultural systems.     

Physiological adaptive mechanisms of plants grown in saline soil and implications for sustainable saline agriculture in coastal zone

There is large area of saline abandoned and low-yielding land distributed in coastal zone in the world. Soil salinity which inhibits plant growth and decreases crop yield is a serious and chronic problem for agricultural production. Improving plant salt tolerance is a feasible way to solve this problem. Plant physiological and biochemical responses under salinity stress become a hot issue at present, because it can provide insights into how plants may be modified to become more tolerant. It is generally known that the negative effects of soil salinity on plants are ascribed to ion toxicity, oxidative stress and osmotic stress, and great progress has been made in the study on molecular and physiological mechanisms of plant salinity tolerance in recent years. However, the present knowledge is not easily applied in the agronomy research under field environment. In this review, we simplified the physiological adaptive mechanisms in plants grown in saline soil and put forward a practical procedure for discerning physiological status and responses. In our opinion, this procedure consists of two steps. First, negative effects of salt stress are evaluated by the changes in biomass, crop yield and photosynthesis. Second, the underlying reasons are analyzed from osmotic regulation, antioxidant response and ion homeostasis. Photosynthesis is a good indicator of the harmful effects of saline soil on plants because of its close relation with crop yield and high sensitivity to environmental stress. Particularly, chlorophyll a fluorescence transient has been accepted as a reliable, sensitive and convenient tool in photosynthesis research in recent years, and it can facilitate and enrich photosynthetic research under field environment.     

Comparative analysis of endophytic bacterial diversity between two varieties of sunflower Helianthus annuus with their PGP evaluation

Endophytic bacterial diversity shows an intricate network of interactions with host plants as they reside in various tissues and organs at certain stages or all stages of their life cycle stimulating the plant growth and fitness. Sunflower is a trendy oilfield crop and variation in its varieties is associated with the dynamics of endophytic diversity. The present study is undertaken to identify and compare the ecological niche of endophytic bacterial communities amongst different tissues of two hybrids varieties Hysun-33 and Hysun-39 of sunflower (Helianthus annuus) at three developmental stages which are vegetative stage I (after 15 days of seeds germination), vegetative stage II (after 30 days of germination) and reproductive stage (after 90 days of germination). A total of 74 endophytes from Hysun-33 and 115 endophytes from Hysun-39 have been isolated from different tissues and growth stages. Amongst plant parts, root tissues harbored higher bacterial inhabitants (44) followed by stem (33), leaf (30) and flower (7) of Hysun-39. Likewise, Hysun-33 endophytes colonized roots more abundantly followed by leaves, stem and flowers. All strains are found to be gram positive with the exception of only RA9 from Hysun-33 and RB9 from Hysun-39 that are gram negative. Among different growth stages, the maximum bacterial population (CFU of 320 × 10³) was found amongst root microflora at vegetative stage II of plant in Hysun-39 variety as compared to root endophytes of Hysun-33 having (CFU of 10 × 10³). The evaluation of their growth promoting features revealed that among 74 isolates of Hysun-33, 70% exhibited the ability of hydrogen cyanide production, 43% IAA production, 36% siderophore production and 4% nitrogen fixation and also phosphate solubilization. However among 115 isolates of Hysun-39, 64% appeared as hydrogen cyanide producers, 56% IAA producers, 33% siderophore producers, 2% nitrogen fixers and 4% as phosphate solubilizers. Therefore our study reveals understanding of wide-ranging diversity of endophytic bacteria and their beneficial relationship with internal tissues of host plant which may recommend their implementation to crops for better development of agricultural systems.