Genetically modified crops: methodology, benefits, regulation and public concerns. (9/1185)

The genetic modification of crop plants from the methodology involved in their production through to the current debate on their use in agriculture are reviewed. Techniques for plant transformation by Agrobacterium tumefaciens and particle bombardment, and for the selection of transgenic plants using marker genes are described. The benefits of currently available genetically modified (GM) crops in reducing waste and agrochemical use in agriculture, and the potential of the technology for further crop improvement in the future are discussed. The legal requirements for containment of novel GM crops and the roles of relevant regulatory bodies in ensuring that GM crops and food are safe are summarized. Some of the major concerns of the general public regarding GM crops and food: segregation of GM and non-GM crops and cross-pollination between GM crops and wild species, the use of antibiotic resistance marker genes, the prevention of new allergens being introduced in to the food chain and the relative safety of GM and non-GM foods are considered. Finally, the current debate on the use of GM crops in agriculture and the need for the government, scientists and industry to persevere with the technology in the face of widespread hostility is studied.  (+info)

Crop improvement in the 21st century. (10/1185)

Crop yields increased dramatically in the 20th century as recorded on Broadbalk or in world averages. The vast majority of that increase has occurred since the last world war and has been powered by changes in the genetic potential of the crop and in the way in which it has been managed. Nevertheless, the challenge to feed a world population that is likely to rise to 8 billion is formidable, particularly since recent analyses suggest that the rate of increase in yields of several crops may have dropped over the last decade. What are the opportunities to meet this challenge and to continue to improve the yields of our crops? Improvements in agronomy are likely to be more concerned with efficiency and elegance rather than in major breakthroughs. More sophisticated crop protection chemicals designed on the basis of vastly increased screening potentials and (at last?) possibilities of rational design will be supplemented by a battery of decision support systems to aid management choices which can be precisely implemented. Genetic improvement is the area in which to-look for the major breakthroughs. The broad potential of recombinant DNA technology will provide the possibility of both molecular analyses of crop productivity and ways in which it may be possible to improve that productivity. The goal of analysis may be approached in three ways: starting at the beginning by generating complete sequences of the plant genome; starting at the end by genetic analysis of phenotypes using genetic marker technology; or, starting in the middle, by metabolic analysis. Improvements may be obtained by re-assorting what has been achieved through enhanced breeding technologies, by randomly induced change, and by generation of totally new possibilities through biochemical engineering. Examples of all approaches will be given. The onset of genomics will provide massive amounts of information, but the success will depend on using that to improve crop phenotypes. The ability to meet the challenges of the 21st century will depend on the ability to close that 'phenotype gap'.  (+info)

Wild barley: a source of genes for crop improvement in the 21st century? (11/1185)

The development of new barleys tolerant of abiotic and biotic stresses is an essential part of the continued improvement of the crop. The domestication of barley, as in many crops, resulted in a marked truncation of the genetical variation present in wild populations. This process is significant to agronomists and scientists because a lack of allelic variation will prevent the development of adapted cultivars and hinder the investigation of the genetic mechanisms underlying performance. Wild barley would be a useful source of new genetic variation for abiotic stress tolerance if surveys identify appropriate genetic variation and the development of marker-assisted selection allows efficient manipulation in cultivar development. There are many wild barley collections from all areas of its natural distribution, but the largest are derived from the Mediterranean region. The results of a range of assays designed to explore abiotic stress tolerance in barley are reported in this paper. The assays included; sodium chloride uptake in wild barley and a mapping population, effects for delta 13C and plant dry weight in wheat aneuploids, effects of photoperiod and vernalization in wild barley, and measurements of root length in wild barley given drought and nitrogen starvation treatments in hydroponic culture. There are examples of the use of wild barley in breeding programmes, for example, as a source of new disease resistance genes, but the further exploration of the differences between wild barley and cultivars is hampered by the lack of good genetic maps. In parallel to the need for genetic studies there is also a need for the development of good physiological models of crop responses to the environment. Given these tools, wild barley offers the prospect of a 'goldmine' of untapped genetic reserves.  (+info)

Selectable traits to increase crop photosynthesis and yield of grain crops. (12/1185)

The grain yield of cereals has almost doubled this century as a result of genetic manipulation by plant breeding. Surprisingly, there has been no change in the rate of photosynthesis per unit leaf area to accompany these increases. However, total photosynthesis has increased as a result of an increase in leaf area, daily duration of photosynthesis or leaf area duration. There remain substantial opportunities to continue to improve total photosynthesis and crop yield genetically using conventional breeding practices. Selectable traits are discussed here in the context of increasing total above-ground biomass under favourable conditions. Opportunities exist to alter crop duration and the timing of crop development to match it better to radiation, temperature and vapour pressure during crop growth, and to increase the rate of development of early leaf area to achieve rapid canopy closure. The importance of these traits will depend on the environment in which the crop is grown. Increases in crop photosynthesis through breeding are also likely to come via indirect means. Selection for a high and sustained stomatal conductance during the period of stem elongation is one way. Increasing assimilate allocation to the reproductive primordia so as to establish a large potential sink should also indirectly increase total crop photosynthesis. Evidence in the major grain crops suggests that by anthesis the capacity for photosynthesis is high and that photosynthesis is not limiting during grain filling. To use this surplus capacity it is suggested that carbon and nitrogen partitioning to the reproductive meristem be increased so as to establish a high potential grain number and the potential for a large grain size. It is then expected that additional photosynthesis will follow, either by a longer daily duration of photosynthesis or by an extended leaf area duration.  (+info)

Transgenic approaches to crop improvement. (13/1185)

Transgenic crops are now grown commercially on several million hectares, principally in North America. To date, the predominant crops are maize (corn), soybean, cotton, and potatoes. In addition, there have been field trials of transgenics from at least 52 species including all the major field crops, vegetables, and several herbaceous and woody species. This review summarizes recent data relating to such trials, particularly in terms of the trends away from simple, single gene traits such as herbicide and insect resistance towards more complex agronomic traits such as growth rate and increased photosynthetic efficiency. Much of the recent information is derived from inspection of patent databases, a useful source of information on commercial priorities. The review also discusses the time scale for the introduction of these transgenes into breeding populations and their eventual release as new varieties.  (+info)

Plant hydraulic conductance measured by the high pressure flow meter in crop plants. (14/1185)

A new high pressure flow meter (HPFM) method for measuring plant hydraulic conductances (K) was investigated to examine whether its results are comparable to those from a conventional evaporative flux (EF) method in crops. Hydraulic conductance (K) was measured by the two methods under quasi-steady-state conditions in six crops grown in pots: soybean (Glycine max L. Merr. cv. Tsurunoko daizu), sunflower (Helianthus annuus L. cv. Russian mammoth), kidney bean (Phaseolus vulgaris L. cv. Tsurunashi morocco), tomato (Lycopersicon esculentum Mill. cv. Sekai-ichi), green pepper (Capsicum annuum L. cv. shishitou), and eggplant (Solanum melongena L. cv. Seiguro chunaga nasu). There was a 1:1 agreement between K values measured by the two methods for K values of whole plant, root and stem, and leaf under quasi-steady-state conditions. Leaf water potential (psi leaf) and evaporative flux density (E) in sunflower was curvilinear, indicating whole plant K estimated by the EF method increased with increase of E. Predicted psi leaf (= E divided by whole plant K measured by the HPFM method) agreed with measured psi leaf. Diurnal changes were also found in K measured by the HPFM confirming that K changed in response to temperature and E. The HPFM revealed that variable conductance was located in all organs: roots, stems, petioles, and leaves. These observations indicated that the HPFM is valid for crops as well as for trees (as previously established by Tsuda and Tyree) and has advantages over the EF method because of the speed and ease of the HPFM method.  (+info)

Predictions of biodiversity response to genetically modified herbicide-tolerant crops. (15/1185)

We simulated the effects of the introduction of genetically modified herbicide-tolerant (GMHT) crops on weed populations and the consequences for seed-eating birds. We predict that weed populations might be reduced to low levels or practically eradicated, depending on the exact form of management. Consequent effects on the local use of fields by birds might be severe, because such reductions represent a major loss of food resources. The regional impacts of GMHT crops are shown to depend on whether the adoption of GMHT crops by farmers covaries with current weed levels.  (+info)

Regulation of leaf and fruit growth in plants growing in drying soil: exploitation of the plants' chemical signalling system and hydraulic architecture to increase the efficiency of water use in agriculture. (16/1185)

In this paper the nature of root-to-shoot signals in plants growing in drying soil is considered in the context of their commercial exploitation in tomato (Lycopersicon esculentum L.) and other crops. Recent findings are presented on the effects of partial root drying (PRD) in the production of a glasshouse tomato crop. These findings show how an understanding of both root-to-shoot signalling mechanisms and fruit hydraulic architecture may explain observed increases in fruit quality, the differential effects of PRD on vegetative and reproductive production and the incidence of blossom end rot. Evidence is provided to support the hypothesis that the success of PRD may lie, at least in part, in the relative chemical and hydraulic isolation of the tomato fruit.  (+info)