Accurate quantitative assessment of the benefits accruing from the genetic improvement of crops is difficult. Crop yield increases are achieved through the introduction of new, improved varieties, through improvements in cultural practices and as a consequence of interactions that occur between new varieties, cultural practices and environmental conditions. Part of the yield increases from new varieties is as a consequence of genetic plant resistance to pests and diseases. Plant breeding, which is dependent on there being available a wide relevant genetic base for each crop, has also provided considerable improvements in quality, as well as improving adaptability to a wider range of environments.

In the developed world estimated annual yield increases from the genetic improvement of crops, especially cereals, are of the order of 1–2%. Examples are given from a number of crops of hybrid varieties, of varieties with improved quality and of varieties that are genetically resistant to pests and diseases to illustrate that conventional plant breeding, allied to multi-disciplinary, strategic research, has been very effective, both economically and in protecting the environment.

The adoption of emerging biotechnological methods in plant breeding is presented discussing specifically the relevance of cell genetics to potato improvement. The finding and use of efficient anther plant producing strains of potato (EAPP clones) is first discussed. This is followed by the presentation of recent progress toward the obtaining of diploid potato strains producing a high percentage of monohaploids from anthers. The selection of homozygous diploid regenerants (potato ‘pure lines’) by using an RFLP approach is also presented. A summary chart is presented, containing the description of an integrated breeding procedure that may be considered for future breeding of this species.

The usefulness of restriction fragment length polymorphisms (RFLPs) in plant breeding and genetics is discussed, with particular emphasis on tagging genes, map-based cloning, the assessment of genetic variability and distances, and comparative genome mapping.

The Department of Plant Breeding and Biometry has currently established tight linkages between RFLPs and more than 20 genes of economic importance. Approximately half of these genes confer resistance to major pathogens including nematodes, bacteria, fungi, and viruses. Other genes tagged are involved in various aspects of crop quality.

Locating genes with respect to DNA markers on an RFLP map provides a starting point for cloning the genes by chromosome walking. This strategy is currently being pursued for three disease-resistance genes that have been placed on the tomato RFLP map; Pto (resistance to Pseudomonas syringae), Mi (resistance to root-knot nemotodes) and Tm2a (resistance to tobacco mosaic virus). Further discussion will include the construction of a yeast artificial chromosome library and the collection of additional DNA markers in the regions of interest through RAPD analysis of nearly isogenic lines.

The assessment of genetic variability and fingerprinting varieties based on RFLP data will be briefly discussed.

Comparative genome mapping in the family Solanaceae has allowed the relationships among tomato, potato, and pepper to be unravelled. Tomato and potato share a near perfect conservation of gene order throughout their genomes. In contrast, while pepper shares most of its single copy DNA with tomato and potato, the order of these markers is highly rearranged compared with the other two species.

Pre-messenger RNA (pre-mRNA) splicing or the removal of introns from pre-mRNA transcripts is a key process in the maturation of mRNA. This process requires the assembly of a large complex of RNA and protein molecules, called the splicosome, on the pre-mRNA transcripts. Molecular and biochemical analyses of plant intron sequence and structure and of the components of the plant spliceosome are providing information on the mechanism of intron recognition and splice site selection in both monocoty-ledonous and dicotyledonous plants. This knowledge will help in gaining an understanding of phenomena such as the difference in splicing between monocotyledonous and dictoyledonous plants, the enhancement of gene expression brought about by the presence of some introns and alternative splicing. The importance of introns and pre-mRNA splicing to accurate and regulated gene expression, therefore, is of direct relevance to transgene expression and genetic manipulation.

Crop protection against pests and diseases is of prime importance and plays a major role in agricultural production both in the Developed and Developing parts of the world.

Although chemical pesticides have been in use for a long time it is only since the Second World War that a very heavy and almost exclusive reliance has been placed upon their use. This, in many cases, has resulted in the rapid build-up of resistance by insect pests to such compounds, as is illustrated by the rapidly developed resistance to the organochloride insecticides by the cotton bollworm, Heliothis virescens. Indeed, there are many examples of resistance in a major pest being observed within the first year of field use (Metcalf 1986). In some cases the indiscriminate application of pesticides has exacerbated the problem of insect herbivory where elimination of a wide range of predatory species along with the primary pests has resulted in secondary pests becoming primary pests themselves with even more devastating effects (Heinrichs & Mochida 1983).

Some of the most successful early applications of genetic engineering in crop improvement have been in the production of virus-resistant plants. This has been achieved not by the transfer of naturally occurring resistance genes from one plant species or variety to another but by transformation with novel resistance genes based on nucleotide sequences derived from the viruses themselves or from virus-associated nucleic acids. Transformation of plants with a DNA copy of the particle protein gene of viruses that have positive-sense single-stranded RNA genomes typically confers resistance to infection with the homologous and closely related viruses. Transformation with a gene that is transcribed to produce a benign viral satellite RNA can confer virus-specific tolerance of infection. In addition, recent work with viral poly-merase gene-related sequences offers much promise, and research is active on other strategies such as the use of virus-specific ribozymes.

Already the field trialling of plants incorporating transgenic virus resistance has begun, with encouraging results, and effects on virus spread are being studied. Deployment strategies for the resistant plants must now be devised and the conjectural hazards of growing them assessed. Genetically engineered virus resistance promises to make a major contribution to the control of plant virus diseases by non-chemical methods.

Ripening of tomato and other fruits involves changes in quality attributes that make them attractive to consumers. These alterations are brought about by the coordinated expression of specific genes. Ethylene, synthesised by cells of climacteric fruit at the onset of ripening, stimulates the expression of genes required for ripening to occur. Experiments with transgenic plants have shown that a 5′ flanking region from the fruit polygalacturonase (PG) gene directs the ripening-specific expression of foreign genes in tomato. Antisense genes have also been used to down-regulate expression of the PG gene, causing a reduction in pectin degradation during ripening. This reduction in PG has beneficial effects on fruit storage life and processing characteristics. Antisense technology has also been used to assign functions to previously unknown genes. This has led to the identification of the gene for ethylene forming enzyme (EFE) which catalyses the terminal step in ethylene synthesis. Detached fruit from tomato plants in which EFE is inhibited by antisense genes produce much less ethylene and ripening is greatly slowed. The rate of ripening can be restored by adding ethylene externally. These results raise the possibility of manipulating ripening of many fruits and also of controlling processes such as abscission and senescence of leaves and flowers.

Genetic variation within a crop species is often limited and restricts improvement by conventional breeding methods. This is particularly true for environmental stresses, both biotic and abiotic. Wild relatives of crop plants, however, provide a rich source of novel variation which can be introduced into the crop. Many alien genes for biotic stress resistance have already been introduced into crops; in contrast, the genetic control of abiotic stress tolerance is poorly understood. Genetic engineering of abiotic stress tolerance in the Triticeae is the main subject discussed here with particular reference to salt tolerance in wheat and barley. Methods of alien gene transfer, including locating tolerance genes and restructuring chromosomes, are described. One of the major limitations in transferring genes for stress tolerance is the lack of good tests for resistance or tolerance which is largely due to the fact the physiological mechanisms involved are not fully understood. Genetic markers provide a new opportunity of detecting chromosome segments carrying desired genes easily and efficiently, and these will become increasingly important as the genetic maps of crop species are expanded. Although many stress genes have been located to specific chromosomes, and some have been mapped intra-chromosomally and their dominance relations determined, there is a great lack of knowledge of the control of these genes at the molecular level. Molecular studies of this type are difficult, but it is anticipated that the limitations will be overcome in the near future.

In tomato (Lycopersicon esculentum Mill.), extensive variation can be observed in genes conditioning many plant functions including disease resistance, plant development, and fruit, leaf and hypocotyl pigmentation. Genes exist that confer resistance to viruses, nematodes, bacteria and fungi. There is great value in developing a facile system for isolating such genes, and we are attempting to create a tomato gene isolation system based on insertional mutagenesis with the maize transposon Ac. Our chosen target genes (Cf-2, Cf-4, Cf-5 and Cf-9) confer resistance to specific races of the fungus Cladosporium fulvum Cooke, the causal agent of leaf mould. We have used classical and molecular techniques to map three of these genes, correcting errors in previous reports. Ac-carrying T-DNA constructs have been developed to facilitate monitoring of Ac activity in tomato, where Ac is extremely active. These constructs have been used in plant transformation experiments, and over 100 tomato lines carrying Ac have been created. More than 20 T-DNAs carrying Ac have been localised on the tomato genetic map by testing linkage to RFLP loci. This was carried out to exploit the preference of Ac for transposition to linked sites in our tagging strategy.

The successful utilisation of recent advances in plant biotechnology for the benefit of mankind, with the avoidance of fundamental mistakes that could lead to environmental disaster, requires wise and balanced legislation. In addition, the conservation of the habitats and germplasm so essential to plant breeding requires carefully planned management of resources. These, however, depend upon an informed public with a sensitivity to, and knowledge and understanding of, the issues at stake. It is the people, after all, who influence decision making by governments, through the ballot box or through the pressure of public opinion. Botanic Gardens have a vital role to play in public education, and have the capacity to become the shop windows for the whole of plant science.

Four examples of public education in plant biology being developed at the Royal Botanic Garden Edinburgh are considered, as follows:

(i) Public information, as exemplified by the provision of information about plants, lectures about plants and the development of ecological plantings and displays relating to agriculture, plant breeding and conservation.

(ii) Contact through art, as exemplified by the Andy Goldsworthy retrospective exhibition of 1990 and the 1991 exhibitions of the work of Redouté and Margaret Stones, in which the media of sculpture and painting inspired by the natural world have been used to build bridges between plant science and the wider public.

(iii) Education in primary schools, as exemplified by the ‘Living in a Rainforest’ project, in which young people and their teachers spend periods of time in a replica of a Bornean longhouse and through this experience develop an understanding of the importance of the balance between people and the complex ecosystem of the rainforest.

(iv) Education in secondary schools, as exemplified by the Science and Plants for Schools project in which rapid cycling Brassica rapa and other materials are used in the development of new and exciting approaches to the teaching of experimental plant science, genetics and breeding.

The ways in which projects such as these can be designed to convey important messages concerning plant breeding, genetic engineering, germplasm and habitat conservation and the role of plants in the world economy are discussed, and ideas for other approaches to public education in the Royal Botanic Garden Edinburgh are outlined.

Plants, animals and microorganisms are being manipulated to improve their characteristics for commercial purposes. Some manipulated organisms will be grown under containment and only released to the environment accidentally and, usually, in relatively small numbers. Others, such as crop plants, will be grown on a large scale in the open environment. There is concern that modified organisms may become pests, or will produce pests as a result of mating with other organisms in the environment.

This paper will discuss some of the issues involved in deciding whether genetically modified plants should be released to the environment or not.

The cost of patenting an invention should be incurred only where the patent is likely to give the inventor an economic or a tactical advantage. Where it is practicable, secrecy may be preferable to patenting. If an advantage from patenting can be envisaged, then in Western Europe the inventor can apply either for a European patent under the European Patent Convention or for a national patent. The inventor in plant biotechnology faces a ban on patenting certain inventions, including plant varieties and essentially biological processes for the production of plants. But since this ban is interpreted strictly, there are opportunities for patenting what at first glance might seem not patentable. A patent application must give a written description of the invention that is complete enough for a skilled person to reproduce it. The inventor may be required to supplement the description in a patent specification for a biotechnological invention, by depositing a sample of relevant biological materials. A European patent is treated as a national patent in the country for which it was granted. Since a patent may be invalidated in enforcement proceedings, patenting may turn out to have been a costly mistake.

Plant biotechnology can serve industrial concerns in two ways; it can lead to new products and to new ways of producing an existing product (i.e. ‘processes’). The technology can be used in any business involved in using or selling plant products. In the agricultural input business molecular genetics is having most effect on the introduction of new variation into crop plants. The first products are likely to involve the introduction of insect and disease resistance and herbicide tolerance; some genes transferred will change product quality. Future applications will involve the control of more complex traits. Biotechnology will also enhance plant breeding via improved technologies (e.g. RFLPs and tissue culture); also the production of hybrids is likely to be enhanced and extended. Early products will also include the production of rDNA microbial products for control of pests and diseases.

Of considerable concern to businesses is whether or not they can make sufficient financial return on plant biotechnology. The reasons behind this concern are the time it takes to introduce a product to the market; the expenditure on meeting regulatory requirements; the overall level of public acceptance of the products and the level of return from the farmer. To ensure a fair return on investment there also needs to be a secure structure of intellectual property protection (patents, plant breeders rights, etc.). Continued success in the application of plant science to agricultural improvement depends on a proper economic environment as well as the advancement of the science.

Advances in biotechnology are creating opportunities to increase food production in developing countries and reduce or eliminate the environmental problems associated with conventional farming practices. International agricultural research centres have used the techniques of modern molecular biology for more than a decade, mostly for tissue culture and the elimination of virus diseases in planting materials. As the centres expand their use of the new tools of biotechnology, the focus of their work is shifting. The centres are playing an even larger role in linking developing countries' scientists with colleagues in public and private sector institutions in the developed world. They are also using the new techniques to speed up the development of pest- and disease-resistant crop varieties. Whenever possible they are developing collaborative links with institutions that have the experience and infrastructure needed to carry out advanced molecular research, thus minimising the need for expensive, highly sophisticated in-house capabilities.

In Chapter 11 of Our Mutual Friend, Dickens noted that “Mr Podsnap had even acquired a peculiar flourish of his right arm in often clearing the world of its most difficult problems, by sweeping them behind him”. With a surname redolent of a kitchen botanist, Mr Podsnap no doubt realised that problems are mere opportunities for the theatrically dextrous. Perhaps the act of sweeping provides forward momentum to capitalise on yet more problems. In plant biotechnology, many of the problems confronting mankind are opportunities to employ exciting science.