Wheat genetic resources
B. Skovmand, S. Rajaram, J.M. Ribaut, A.R. Hede

Agricultural practices prior to the eighteenth century were completely dependent on crop landraces and mixtures of these landraces. The Industrial Revolution followed with an associated population explosion that transformed the subsistence nature of agriculture and its farming systems forever. In the midnineteenth century, Mendel (and later other pioneering plant geneticists) provided knowledge of plant genetics that made it possible to dramatically increase the production potential of agriculture. Undeniably, the wonders of crop improvement have resulted in the erosion of genetic diversity of many crops in farmers’ fields, including wheat, due to the replacement of landraces and farmers’ old cultivars with modern high-yielding cultivars.

Genetic resources are fundamental to sustaining global wheat production now and in the future. They embody a wide range of genetic diversity that is critical to enhancing and maintaining the yield potential of wheat, for they provide new sources of resistance and tolerance to biotic and abiotic stresses. Modern high-yielding wheat cultivars are an assembly of genes or gene combinations pyramided by breeders using, in most cases, well-adapted cultivars from their regions. International agriculture research has enormously expanded the availability of widely adapted germplasm that is genetically diverse (i.e. descended from more sources). However, introgression of additional variation found in genetic resources is necessary to increase yield stability and further improve wheat.

GENETIC RESOURCES

Genetic resources have been categorized by Frankel (1977) and the Food and Agriculture Organization of the United Nations Commission on Plant Genetic Resources (FAO, 1983), though this categorization is not followed by all centres involved in genetic resource conservation and utilization. These categories are:

• modern cultivars in current use;

• obsolete cultivars, often the elite cultivars of the past and often found in the pedigrees of modern cultivars;

• landraces;

• wild relatives of crop species in the Triticeae tribe;

• genetic and cytogenetic stocks;

• breeding lines.

These genetic resources are the gene pool available for breeders and other scientists, and in the Triticeae tribe several pools are recognized (Von Botmer et al., 1992) (Table 5.1). The primary gene pool consists of the biological species, including cultivated, wild and weedy forms of a crop species. Gene transfer in the primary gene pool is considered to be easy. In the secondary gene pool are the coenospecies from which gene transfer is possible but difficult, while the tertiary gene pool is composed of species from which gene transfer is very difficult.

GENETIC EROSION AND CONSERVATION

The modern semidwarf cultivars of crops such as wheat and rice are largely to blame for the genetic erosion that has resulted in the displacement of wild relatives and landraces of crop species in their regions of origin. However, this was in reality the second erosion. The first genetic erosion started more than two centuries ago when more intensive farming methods were introduced (Porceddu et al., 1988) and when farmer selection within local cultivars was used, followed by their replacement by introductions from other areas, and once the knowledge of the hereditary mechanisms became understood, by cultivars originating from hybridization.

TABLE 5.1
Genomic formula and synonyms when Aegilops and Amblyopyrum are placed within Triticum

Source: van Slageren, 1994.

The second genetic erosion was a consequence of the accelerated population increases that followed World War II. Introduction of modern cultivars was and is essential to provide sustenance; denial of the utilization of improved cultivars would have resulted in starvation and malnutrition through reduced crop production. The logical alternative to the resulting genetic erosion was to conserve the landraces and wild relatives to avoid the loss of this natural resource.

The conservation of genetic resources in the various crop species is essential, as they will supply the variation needed to provide adequate food in the future. In some instances, these biological resources have been lost due to ignorance or late realization of their importance. However, in the last 30 years, efforts have been made to preserve the natural variation in the more important food crops. The Food and Agriculture Organization of the United Nations (FAO) through its Commission on Genetic Resources for Food and Agriculture and the International Plant Genetic Resources Institute (IPGRI), as well as its predecessor, the International Board of Plant Genetic Resources (IBPGR), have played an active role in this arena.

Genetic resource conservation rests on its commitment to sustaining the productivity of agricultural resources in developing countries today and for the future. To this end, genetic resources need to be preserved, protected and made available to all that need them. The FAO International Treaty adopted the concept that access to genetic resources should be facilitated for plant breeding and other such research activities. Many collections had until now operated under this concept (Skovmand et al., 1992). The concept was reinforced when the Consultative Group for International Agriculture Research (CGIAR) signed an agreement with FAO placing all preConvention on Biological Diversity (CBD) collections, currently maintained in CGIAR centres, under the jurisdiction of the FAO.

WHEAT COLLECTION NEEDS

Although considerable wild and landrace wheat germplasm has been collected since 1989, there are still large gaps in world collections. The reasons why Croston and Williams (1981) assigned first priority to wheat among all crops for collection and preservation still pertain. Wild wheats and landraces, especially material adapted to microhabitats, are rapidly disappearing because of the introduction of agronomically superior new cultivars. Severe overgrazing by huge flocks of sheep and goats in the Near East and Central Asia can, in a very few years, wipe out late-flowering Aegilops and Triticum species in preference to earlier flowering, wild annual barley, perennial barley (Hordeum bulbosum) and wild oats, which are less affected by animal grazing. Moreover, the direct wild ancestors of cultivated wheats, namely Ae. speltoides, T. urartu, T. monococcum ssp. aegilopoides, T. turgidum ssp. dicoccoides and T. timopheevii ssp. Armeniacum, are especially susceptible to overgrazing and to increased cultivation of previously seasonal grasslands. There is a need to preserve as much of the existing genetic variation as possible for future breeders and consumers to ensure availability of genes for yield and tolerance to environmental and biological stresses.

There are still three major and critical collection needs for wheat germplasm (Waines and Skovmand, 1996). The first need is for the continued collection of wild relatives of wheats in the regions where they are native. The second need is for the collection of landraces in places such as Guatemala where they have not been collected before. The third need is for the acquisition of improved germplasm with specific traits from breeding programmes and obsolete and new cultivars from countries around the world.

The centre of variation for wild wheat relatives includes: Egypt, Israel, Jordan, Lebanon, Syria, Turkey, Armenia, Azerbaijan, Iraq, Iran, Afghanistan and the Turkic Republics of Central Asia. Some of these countries are not easily accessible. However, some are becoming accessible for collection expeditions and cooperative work. The range of distribution of wheat relatives occurs from the Canary Islands to western China, and from southern Russia to northern Pakistan and India (van Slageren, 1994).

Principal regions for future collection

Former Yugoslavia, Albania and Greece

These countries are relatively accessible and contain 13 species of wild wheat relatives, such as Ae. uniaristata and associated species, some of which possess heavy metal tolerance. The original collection site of Ae. uniaristata in Turkey is now absorbed into the suburbs of Istanbul. However, effort should be made to find this taxon at other adjacent locations in European and Asiatic Turkey.

Western Mediterranean

The countries include Portugal, Spain, southern France, Morocco, Algeria and Tunisia. Most are accessible and harbour eight or more species. In northern Portugal, there are landraces of wheat and rye adapted to unidentified soil problems. There are also primitive wheats, such as spelt, dicoccum and monococcum, that are still grown in Spain for specific culinary or animal uses. In North Africa, there are landraces of diploid, tetraploid and hexaploid wheats that may exhibit physical environmental stress tolerances. Collections of Ae. bicornis from the coastal areas of Egypt and Cyprus in the eastern Mediterranean might be useful as a source of salt tolerance.

Syria

Aegilops tauschii is the donor of the DD genome to bread wheat. Its chromosomes have already been connected with several genes for physical and biological stress tolerance, as well as flour quality characteristics. Recently, agronomists working out of the International Center for Agricultural Research in the Dry Areas (ICARDA) found Ae. tauschii var. meyerii growing in the Syrian Desert in the area near Rasafa. It grows as a weed in wheat and barley fields that receive run-off during winter rains. Temperatures in this area rise quickly in mid- to late spring. It is important to determine the extent of this population of Ae. tauschii in the Syrian Desert and to plot the extent of the two tetraploid companion species, Ae. crassa and Ae. vavilovii. Aegilops tauschii also grows in more mesic areas in southeastern Turkey, the northern regions of Iraq, Iran, Pakistan, Kazakhstan (other central republics) and Afghanistan, and into western China (Sinkiang Province). It may follow the so-called Silk Road from Turkey to China. However, the most drought- and heat-stressed of these areas appears to be the Syrian Desert and central and southern Iran.

Outer Mongolia, Tibet and Nepal

Keith Briggs reported early-maturing wheats from Mongolia (K. Briggs, personal communication, 1995). Are these landraces or improved Soviet wheats? The landraces of wheats and barley in the region of Tibet should be collected. A naturally occurring synthetic hexaploid has been reported in Tibet, which should be sought. There are landraces of wheats and barley in the foothills of the Himalayas in Nepal that have never been collected; some of these might be important sources of cold tolerance (E.E. Saari, personal communication, 1996).

Guatemala, Honduras, Peru and Bolivia

There are landraces of wheats found in all of these countries that should be collected. They may date from early introductions by the Spanish.

Eritrea

There are landraces of durum and possibly bread wheats in this area of northeastern Africa.

Niger

Wheat is reported to be grown in a paddy system in the Niger River basin. This system needs to be investigated and germplasm collected to ascertain whether it is useful in areas with a high water-table.

Iran

Seventeen species are found in this region. Although many landraces of wheats were collected in Iran and were available before and after the Islamic Revolution, wild wheat and Aegilops from Iran are still largely uncollected and unknown. The United States Department of Agriculture (USDA) collection has one accession of Triticum urartu, the A-genome donor to durum and bread wheat, from the mountains near Isfahan and one collection from the mountains near Shiraz. Thus the material is known to be there. The mountainous area between Kermanshah, Isfahan and Shiraz needs to be collected for Ae. speltoides, T. urartu, T. monococcum ssp. aegilopoides, T. turgidum ssp. dicoccoides and T. timopheevii ssp. armeniacum, as well as other species of Aegilops. It is not known how far wild wheats extend south of Shiraz. In the Iranian desert, east of the Zagros Mountains, there are drought-tolerant and salt-tolerant goat grasses that have been little collected. Another promising area is the mountain chain that runs from Isfahan to Bam.

Global wheat genetic resources

About 640 000 accessions of Triticum ssp., Aegilops ssp. and X Triticosecale can be found in collections around the world (Table 5.2). The degree of duplication in these is difficult to ascertain without some type of global wheat genetic resources database. Given this situation, the level of priority that should be placed on collecting more materials is uncertain, except where there is a real threat of genetic erosion to native species in specific areas. Accessions in collections around the world may or may not be preserved properly, and some may not even be catalogued. It may thus be more cost effective to place such collections into secure storage than to collect more materials in the field.

TABLE 5.2
Number of accession available in wheat collections around the world

Source: Information collared from IBPGR, 1990.

Conservation can be either in situ or ex situ; in the case of wheat most of the genetic resources have been conserved ex situ. Only in the last few years has in situ conservation been seriously considered, and recently the World Bank has supported such an undertaking in Turkey. The exception is in the natural habitats of eastern Galilee, Israel, where the Ammiad wild wheat study was undertaken in the 1980s. Shands (1991) and Hawkes (1991) summarized a symposium dealing with the findings in this in situ field laboratory. Ex situ conservation of Triticeae genetic resources is easy and cost effective (Pardey et al., 1998), and these genetic resources are adapted to long-term storage conditions.

Documentation

Key to most wheat genetic resource work in the future is the development of a database, or an interconnected system of databases, with the capacity to manage and integrate all wheat information, including passport, characterization and evaluation data. In the early 1990s, the International Maize and Wheat Improvement Center’s (CIMMYT) Wheat Program established just such a strategy for integrating and managing all data pertaining to germplasm regardless of where they were generated (Skovmand et al., 1998). The goal was to facilitate the unambiguous identification of wheat genetic resources and remove barriers to handling and accessing information. As a result, the International Wheat Information System (IWIS), a system that seamlessly joins conservation, utilization and exchange of genetic material, came into being. The system is fast, user-friendly and is available on CD-ROM (Payne et al., 2002; Skovmand et al., 2000a).

The International Wheat Information System has two major components: the Wheat Pedigree Management System, which assigns and maintains unique wheat identifiers and genealogies, and the Wheat Data Management System, which manages performance information and data on known genes. Another information tool, the Genetic Resource Information Package (GRIP), has been developed using IWIS as data warehousing; GRIP, as one of its functions, attempts to collate passport information across gene banks to identify duplications (Skovmand et al., 2000b).

The power of IWIS has been demonstrated in several ways. For example, it has been used to trace genealogies of modern cultivars to their parental landraces or to lines of unknown pedigrees. The system has also revealed that the number of parental landraces in CIMMYT’s bread wheats has increased markedly over four decades, from six ancestors in Yaqui 50 to 68 ancestors in Borlaug M 95. Using information generated by IWIS, cytoplasmic diversity in CIMMYT wheats was found to be restricted (Fox et al., 1994). Other analyses using the system have demonstrated that landraces from certain regions of wheat’s centre of origin do not, or only rarely, appear in the pedigrees of modern wheats. Such genealogical analyses, which could have broad implications for genetic resource utilization, are evidence of the system’s great utility and many potential applications.

Byerlee and Moya (1993) have indicated that 40 million ha in the developing world are sown to wheat cultivars originating directly from CIMMYT crosses or from National Agricultural Research System (NARS) crosses using a CIMMYT parent. In industrialized countries, at least 20 to 25 million ha are sown to cultivars of CIMMYT ancestry. These cultivars are the direct result of active seed exchange between NARSs and CIMMYT over the last three decades, which has made it possible to introduce important traits into widely adapted germplasm. There is no indication that seed exchange will become less important in the future; on the contrary, it will probably be of greater importance. The International Wheat Information System will assist in the exchange of seed and associated information, increase efficiency and minimize unnecessary duplication of evaluations.

Evaluation

Evaluation should be a major activity of germplasm banks to identify useful genetic variation and make it available to breeders.

Variation is needed to:

• increase yield potential; provide new sources of biotic resistance to maintain current yield levels;

• provide adaptation to the more marginal environments (abiotic stress);

• provide improved industrial quality.

Evaluation and pre-breeding should be major activities of any collection. In comparison with many national collections that deal with a multitude of crops, the CGIAR collection based only on Triticeae provides the opportunity and the responsibility to escalate involvement in these activities, in addition to offeing new variation to breeding programmes.

The genetic resources unit uses two evaluation approaches. One is demand-driven, meaning that evaluations are conducted for specific traits or characteristics where the breeding programmes lack variation. The other approach is a systematic evaluation of germplasm groups that the bank considers potential sources of variation for use in breeding programmes. Selecting a specific set of underutilized germplasm and evaluating it for all possible characters does the systematic evaluation of groups of germplasm as potential sources of variation for use in breeding programmes.

A recent study (Gollin et al., 1998) attempts to develop a theoretical model for analysing gene bank decisions regarding the search for traits of economic value in ex situ collections of wheat. In this study, three questions are posed: (i) What is the optimal size of a search among genetic resources of a given type for a trait of economic value? (ii) What is the value of specialized knowledge? and (iii) How should search resources be allocated across types of genetic resources? Results show that the optimal size of a search is sensitive to the economic importance of the problem and the probability distribution of the trait. The cost and time lag associated with pre-breeding techniques imply that in some searches certain categories of genetic resources will be systematically ignored. In another study (Hede et al., 1999), evaluation for heat tolerance traits was accomplished during routine seed multiplication at almost no cost. Both of these studies attempt to design methods or a model to decrease the cost of evaluation. Efficient and cost-effective evaluation is necessary to be able to afford the evaluation need of the future.

Finally, information systems such as the IWIS makes it possible to estimate the degree of relatedness among wheats and allows breeders to increase genetic diversity by selecting materials of divergent parentage for crosses. This can reduce wheat’s vulnerability to diseases and climatic changes, and automatically updates family trees as additional ancestry is discovered.

A recent survey of breeders indicates that 75 percent of wheat breeders acknowledge that future advances in breeding will be limited by a lack of genetic resources, though this was not considered an immediate restraint for most programmes (Rejesus et al., 1996). This lack of genetic resources can be mediated by increasing knowledge about the value of genetic resources and through the identification of new and novel sources of traits, both in the existing ex situ collections and in situ collections yet to be collected.

Utilization

Much has been written about the lack of utility of genetic resources contained in collections, but there has been little attempt to estimate their contribution to wheat improvement. Chapman (1986) examined the role of genetic resources (defined as wild materials and landraces) in wheat breeding and found it difficult to assess. He concluded that genetic resources are used in about 10 percent of crosses, based on the occurrence of genetic resources in pedigrees of recently released cultivars and the frequency of references to genetic resources in the Annual Wheat Newsletter. This task can now be done as described above where pedigree information back to the landrace parents can be displayed.

Surveying the genes originating from wild species and landraces that are being utilized to improve wheat can also assess the contribution of genetic resources. A prime example is the use of dwarfing genes, especially genes Rht1 and Rht2, that became available through the Japanese wheat Norin 10, which in turn inherited them from Shiro Daruma, a Japanese landrace (Kihara, 1983). The incorporation of these dwarfing genes illustrates the difficulty of using genes from unadapted materials, since persistent efforts were required to transfer them into a genotype of value (Borlaug, 1988; Krull and Borlaug, 1970). It also shows that desirable characteristics other than the apparent ones may result from such germplasm. While incorporating strong straw to avoid lodging, better fertility and tillering capacity were obtained by Krull and Borlaug (1970). It is now obvious that dwarfing genes Rht1 and Rht2 have a direct effect on yield over and above the benefits derived from diminished lodging (Gale and Youssefian, 1986).

Another example of the utility of genetic resources is their contribution to improving wheat resistance to the rust diseases. As indicated by Roelfs (1988a), of the 41 known genes for stem rust resistance, 20 originated in species other than T. aestivum and T. turgidum; of the 35 known genes for leaf rust resistance, 12 originated in species other than T. aestivum and T. turgidum. Of the genes originating from T. aestivum for resistance to either rust, a number of these are from landrace cultivars (McIntosh et al., 1998).

One of the stem rust resistance genes, Sr2, originally transferred to hexaploid wheat from Yaroslav emmer by McFadden in 1923 (Stakman and Harrar, 1957), has provided durable resistance to the disease. Cultivars possessing Sr2 in combination with other genes have been grown without stem rust losses on millions of hectares in North America over the last 30 years (Roelfs, 1988b). The tremendous gains in wheat production associated with the so-called green revolution in India and Pakistan would probably not have been realized without the protection from stem rust provided by Sr2 in combination with other genes. For more examples on the role of genetic resources in wheat breeding, see chapter "CIMMYT international wheat breeding".

MOLECULAR BIOLOGY AND FINGERPRINTING

The potential impact of molecular genetics on plant breeding is enormous and not so surprising given the explosion of new molecular technology and applications developed during the last decade. Progress in DNA markers became particularly important with the development of reliable polymerized chain reaction (PCR)-based markers, such as microsatellites and amplified fragment length polymorphism (AFLP). Using DNA markers, linkage maps can be constructed based on allele segregation in a specific cross. By combining this genetic information with suitable phenotypic data, specific DNA regions of interest can be identified and further characterized (e.g. map-based gene cloning) and manipulated (genetic engineering and marker-assisted selection). Furthermore, DNA markers are now used extensively to characterize germplasm (fin-gerprinting), to evaluate the genetic distance among accessions (genetic diversity) and to provide important supportive information to the fields of ecology, population genetics and also evolution.

Among crops, wheat presents a large (about 16 billion base pairs) and complex (hexaploid) genome with a high percentage of repetitive sequences (90 percent), making its study and manipulation quite challenging. The recent development of reliable PCR-based markers represents a major step forward in the study of the wheat genome by providing the tools needed to generate essential knowledge and data in the key areas of fingerprinting and genetic conservation. However, deciding which strategy and DNA marker is most appropriate for a particular investigation is not always straightforward. It depends on a range of factors including principally the nature of the problem and the available resources.

Several fingerprinting studies have already been reported for specific wheat germplasm using several sets of DNA markers, including restriction fragment length polymorphisms (RFLP) (e.g. Paull et al., 1998), micro-satellites (Fahima et al., 1998) and AFLPs (Donini et al., 1997). Fingerprinting, a power-ful application of biotechnology, can be used for among others:

• the genomic characterization, and thus the protection, of specific material;

• the evaluation of the genetic distance among target materials to better characterize the genetic relationships among germplasm (e.g. establishment of genetic pools);

• the identification of duplication within gene bank accessions to ensure the best use of available resources.

Beginning with the initial observations of protein diversity in the 1960s through today’s understanding of variation at the nucleotide level, the development of new molecular markers made possible diverse theoretical and conceptual advances, many of which address conservation issues. DNA markers have a strong role to play in plant genetic resource conservation, notably in the acquisition, main-tenance and characterization of gene bank accessions. For example, DNA markers have been successfully employed to analyse the genetic diversity, within and among groups, in Asiatic wheat landraces (Ward et al., 1998). They were also successfully used to further the understanding of the phylogeny of specific species (Heun et al., 1997). No other type of genetic data has advanced the understanding of the evolutionary process as prominently as molecular markers.

Quantification and classification of diversity in germplasm collections is very important, and DNA markers represent a powerful tool to expand on available information, which is based principally on morphological data. A good genetic of germplasm should help breeding programmes by facilitating the introgression of gene bank accessions in the development of new crosses, thus taking advantage of alleles not found in elite material. Moreover, once a DNA marker is identified for a specific gene of interest in elite germplasm, it can be used to screen gene bank accessions to identify new sources of favourable alleles for the target gene.

Today, molecular tools are available to evaluate and characterize, to a certain extent, genetic diversity among gene bank accessions. One major consideration for the near future is how to manage and efficiently integrate the huge amount of information that may be generated by screening gene bank accessions with DNA markers.

FUTURE UTILIZATION OF GENETIC RESOURCES

As evidenced by the above, genetic resources have played a significant role in wheat improvement and will continue to do so by providing breeders with the variability they require for future improvements. Increases in wheat yield potential to date have resulted mostly from manipulation of a few major genes, such as those affecting height reduction (Rht), adaptation to photoperiod (Ppd) and vernalizing cold (Vrn). Future gains in yield potential, especially under stressed conditions, will almost certainly require exploitation of the largely untapped sources of genetic diversity housed in collections of wheat landraces and wild relatives (Skovmand et al., 2001).

Most wheat breeding programmes dedicate a major portion of their efforts to protecting gains in yield potential by incorporating new and better genes or combinations of genes for disease and pest resistance. Collections of adapted and unadapted wheats have been rich sources of resistance to various diseases, and their greatest underlying value is as a reservoir of undetected resistance genes (Williams, 1989). For most wheat diseases, there is a need to identify more genes for resistance of the hypersensitive type to achieve combinations of genes that confer resistances similar to stem rust resistance, which so far has been very effective. The wild relatives of wheat will most likely be major contributors to this type of resistance.

There is also a need to identify the quantitative type of resistance (partial resistance), characterized by durability and a reduced rate of epidemic build-up (Parlevliet, 1988). This type of resistance may be very important in diseases such as yellow rust, where race-specific resistance has not been long lasting. The most likely sources of quantitative resistance are landraces and obsolete cultivars that have been grown extensively over many years in areas where particular diseases are endemic.

During the late 1980s, the wide crosses research section at CIMMYT expanded its activity to include interspecific hybridization and began exploiting the variability residing in the three genome donors of modern wheat. As a result, more than 500 synthetic wheats having exotic A,B, or D genomes have been produced and are being maintained at CIMMYT. These synthetics are proving to be extremely valuable sources of resistance to various biotic and abiotic stresses, as well as yield-related traits (Mujeeb-Kazi and Hettel, 1995). This is a novel but very efficient way to utilize wheat genetic resources.

The introduction of wheat cropping into marginal areas will present many abiotic stress challenges. Mineral ion deficiencies and toxicities, drought, wind, salinity and temperature extremes are some of the factors that will limit wheat production in these environments. Primitive wheats and wild relatives from the secondary and tertiary gene pools, which originated in such environments, can be expected to provide genes for tolerance to these abiotic stresses.

CONTROL OVER GENETIC RESOURCES

During the 1980s, there was an increasing trend towards a greater application of intellectual property protection (IPP), which contrasted with the 1960s and 1970s where IPP on an international level of plant improvement was seen as a detriment to progress. The view that strong IPP could help in maintaining technological leadership has gained respectability, especially in the United States (Siebeck, 1994). Several international initiatives have resulted, among these the 1991 strengthening of the Union for the Protection of Varieties (UPOV) Convention, which includes a breeder’s exemption to use protected cultivars as parents in breeding. However, according to Siebeck (1994), the most significant initiatives were instigated as part of the Multilateral Trade Negotiating Round in the General Agreement on Tariffs and Trade (GATT), which ended in 1993. At the insistence of the industrial nations, strengthening of IPP was included as a key negotiating point. The efforts in GATT to widen IPP on inventions and breeding technology were paralleled by efforts to regulate international access to genetic resources.

The Food and Agriculture Organization of the United Nations established the International Treaty on Plant Genetic Resources (IT) in 1983, and this Treaty was an attempt to stop genetic erosion and protect genetic resources. At the outset, the International Treaty subscribed to the rule of free interchange of germplasm and recognized plant genetic resources as "heritage of mankind".

The Convention on Biological Diversity, signed in 1992, is an internationally ratified treaty among nations. The CBD officially recognizes sovereign control by individual nations over biological diversity and resources on their territories. The CBD excludes material collected before 29 December 1993, when it entered into force, but any germplasm collected after that date in a country that has signed the CBD comes under the provisions of the Convention. Access to genetic material is regulated on a bilateral basis under the CBD provisions. However, FAO was requested to revise the IT to bring it in conformity with the CBD and introduce provisions to regulate access to collections of genetic resources for food and agriculture, pre- and post-CBD. The IT introduces a multilateral mechanism of access and benefit sharing. Once approved, it will become a binding instrument that will apply to a list of agreed species, including wheat.

One of the results of the discussions on ownership of genetic resources has been the signing of an agreement between CGIAR and FAO where the germplasm collections held in trust by the CGIAR system were placed under the auspices of FAO. The key provisions of the agreement are cited below.

The CGIAR Centres will:

• place their germplasm collections under the auspices of FAO as part of the International Network of Ex Situ Collections;

• not claim ownership or seek IPP over designated germplasm or related information;

• manage designated germplasm according to international standards;

• make the designated germplasm and related information available to users;

• ensure that recipients of designated germ-plasm are bound to the same conditions as the Centres regarding access and IPP.

The FAO will:

• operate the International Network of Ex Situ Germplasm Collections;

• recommend actions required for Centres to adhere to agreed standards;

• assist Centres in evacuation and/or transfer of collections in case of emergencies;

• provide expertise to Centres;

• assist Centres in making germplasm available to users.

These provisions will be modified once the IT is finally approved.

CONCLUDING REMARKS

Most projections suggest that wheat, already the most important food source for human-kind, will also be the primary food staple in the developing world within 15 years. Demand for wheat in developing countries is expected to grow at around 2.2 percent annually, about the same rate as production growth. By the year 2020, the production-consumption gap that is made up by wheat imports could approach 120 million tonnes annually, twice today’s volume (Rosegrant et al., 1995). It was recently postulated that there would be a need to produce 1 billion tonnes of wheat by the year 2020 (Braun et al., 1998). These projections assume that increases in global productivity will meet these demands without real price increases, which is highly desirable for consumers. Since increases in the area sown to wheat are likely to be small, productivity increases will have to come almost entirely from the development and application of new technologies; at the same time, greater sustainability and environmental demands on wheat farming systems will have to be met, and yield stability of the world’s number one food crop maintained.

Genetic improvement of wheat is likely to remain as a major source of productivity gains. The crop’s yield potential has risen about 1 percent annually over the past 30 years. This trend is expected to continue but may require greater breeding resources, especially as recent gains in efficiency that resulted from computerization and mechanization of breeding begin to dwindle. Innovations in molecular biology appear unlikely to effect an impact on yield progress anytime soon. Despite considerable progress in the last 100 years, huge scope still exists for strengthening and making more durable the resistance of wheat to diseases, viruses and insects. This appears to be the area in which molecular biology will make its first impact on wheat breeding. Molecular biology is also likely to aid conventional breeding in changing the quality of wheat grain by developing it for novel industrial uses and improving its nutritional structure in ways that would clearly benefit consumers (increasing its content of available iron, zinc, vitamin A and certain amino acids).

The last 30 years have witnessed an unprecedented level of international wheat germplasm exchange and the development of a greater degree of genetic relatedness among successful cultivars globally; the concept of broad adaptation has thus been well vindicated. However, this is seen by some as increasing genetic vulnerability to pathogens, although such vulnerability depends more on similarities in resistance genes, which may actually be more diverse now than before. Various new factors, including the growing strength of national breeding programmes in the developing world and the advent of breeders’ rights, should result in increased diversity among cultivars and perhaps lead to the exploitation of hitherto-overlooked specific adaptation in wheat. This would be especially important if climate change accelerates. Just as increasing nitrogen supply and improving weed control have been almost universal driving factors of wheat cultivation in the last 50 years, higher atmospheric concentrations of carbon dioxide and global warming with resulting warmer temperatures could significantly influence breeding objectives in the next 50 years.

Genetic resources are fundamental to the world’s food security and central to efforts to alleviate poverty, contribute to the development of sustainable production systems and supplement the natural resource base. The germplasm conserved is especially rich in wild crop relatives, traditional farmer cultivars and old cultivars, which represent an immense reserve of genetic diversity. The material conserved either ex situ or in situ is a safeguard against genetic erosion and a source of resistance to biotic and abiotic stresses, improved quality and yield traits for future crop improvement.

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