Current Geographical Distribution and Habitat of Wild Wheats and Barley - J. Valkoun, J. Giles Waines and J. Konopka
In situ Conservation of Wild Relatives of Crop Plants in Relation to their History - J. Giles Waines
Domestication of Cereal Crop Plants and In situ Conservation of their Genetic Resources in the Fertile Crescent - A.B. Damania
A comprehensive knowledge of the current geographical distribution and habitat of wheat and barley progenitors and close ancestors is important not only for plant scientists but also for archaeologists. The maps of wild wheats and barley distribution by Harlan and Zohary (1966) and Zohary and Hopf (1988) have been the most comprehensive and frequently cited sources of information. Johnson (1975) was probably the first who provided maps of geographical distribution of all four wild Triticum species. However, recent changes in the taxonomic concept of wild wheats and additional information on wild wheats and barley distribution obtained in numerous collecting and/or survey missions to Near East countries call for the production of new updated maps of wild progenitors, ancestors and close relatives of cultivated wheats. The choice of species for the maps was based on their relevance to the discussion on wheat and barley origin and domestication.
Material and methods
In this paper, the nomenclature and taxonomic concept of wild Triticum and Aegilops species is based on van Slageren's monograph (van Slageren 1994), the scientific names and classification of cultivated wheats follow the concept of Dorofeev et al. (1979). The following wild wheat species are recognized and treated in the present paper: Triticum baeoticum Boiss. emend. E. Schiem. (syn. = T. boeoticum) (= T. monococcum L. subsp. aegilopoides (Link.) Thell.), Triticum urartu Tumanian ex Gandilian, Triticum dicoccoides (Koern. ex Asch. & Graebn.) (= T. turgidum L. subsp. dicoccoides (Koern. ex Asch. & Graebn.)) and Triticum araraticum Jakubz. (= T. timopheevi (Zhuk.) Zhuk. subsp. armeniacum (Jakubz.) van Slageren). Other species presented in the distribution maps are: Hordeum spontaneum C. Koch (= H. vulgare subsp. spontaneum), Aegilops speltoides Tausch, Aegilops searsii Feldman & Kislev ex Hammer, Aegilops bicornis (Forssk.) Jaub. & Spach and Aegilops tauschii Coss.
The maps were based on the information in the 'Global database of wheat wild relatives' developed by IBPGR in 1990, now upgraded by and maintained at the Genetic Resources Unit of ICARDA (18,000 entries, data from 52 genebanks). Additional information was obtained in 50 collecting and/or survey missions conducted by ICARDA in collaboration with the respective national programs to Syria, Jordan, Lebanon, Iraq, Iran, Turkey, Armenia, Cyprus, Egypt, Libya, Tunisia, Algeria, Morocco, Bulgaria, former USSR, Turkmenistan, Uzbekistan, Pakistan and Tajikstan. Geographical coverage is limited to the Near East region, which is most relevant to the discussion on wheat and barley domestication. Data for Palestine were not available.
Results and discussion
In barley, there is growing evidence that both two-row and six-row forms of cultivated barley originate from a common wild progenitor, Hordeum spontaneum C. Koch (Zohary and Hopf 1988). Remains of two-row cultivated barley have been recovered from Pre-Pottery Neolithic A (PPNA) sites (ca. 10,000 BP), while six-row cultivated barley has been found somewhat later, in Pre-Pottery Neolithic B (PPNB) sites (Willcox 1991). Figure 1 was produced using only ICARDA database information, because no global database was available. Consequently, there is a concentration of wild barley sites in the western part of the Near East arc, to which most ICARDA survey or collecting missions were targeted. Hordeum spontaneum is better adapted to low-rainfall conditions and less-fertile soils than wild wheat, as is indicated by its presence in the dry sites of central Syria, northern Jordan and northern Iraq.
Wild diploid wheats
Most treatments on geographical distribution of wild einkorn do not recognize the existence of two wild diploid wheats, T. boeoticum and T. urartu. However, there has been growing evidence indicating that the two forms are not only separated by crossing barriers (Johnson and Dhaliwal 1976) but they also differ in plant morphology (Gandilian 1972; Dorofeev et al. 1979) and biochemical and molecular markers (Jaaska 1974; Johnson 1975; Dvorák et al. 1988). Moreover, as Figures 2 and 3 show, they differ in their geographical distribution. Triticum urartu is present in Jordan and the Hauran and Jebel Al Arab region in southern Syria, while the species is missing west of the Near East arc. In general, T. urartu geographical distribution resembles that of T. dicoccoides (Fig. 4) to which it donated the A genome (Dvorák 1976). Sites of T. boeoticum are concentrated in southeastern Turkey, where this species was probably domesticated (Heun et al. 1997). The current distribution indicates that its weedy races have spread with cultivated cereals far to the west and east.
Wild tetraploid wheats
The two wild tetraploid wheat species - T. dicoccoides and T. araraticum - are relatively similar in plant morphology, but they differ in their genomic constitution: AABB in the former and AAGG in the latter. Cultivated emmer [Triticum dicoccum (Schrank) Schuebl.] was domesticated in the Near East from the wild emmer wheat (T. dicoccoides) some 10,000 years ago and, somewhat later, durum and bread wheats were derived from this first cultivated wheat (Zohary and Hopf 1988). Triticum araraticum was probably also domesticated but its cultivated form, Triticum timopheevi (Zhuk.) Zhuk., was found to be grown in a small area in western Georgia together with its hexaploid derivative Triticum zhukovskyi Menabde et Erizjan and cultivated einkorn, Triticum monococcum L. (Dorofeev et al. 1979).
Geographical distribution of T. dicoccoides and T. araraticum is presented in Figures 4 and 5, respectively. The two species are sympatric in the northern and eastern parts of the Near East arc and the dicoccoides wheat is most frequent in its southwestern region, where the araraticum wheat is absent. On the other hand, the distribution of the latter species extends to Transcaucasia, while T. dicoccoides does not occur north of southeastern Anatolia of Turkey. The absence of T. araraticum in Palestine, Jordan and southern Syria may be significant in the discussion on the origin of cultivated tetraploid wheats.
Fig. 1. Distribution of Hordeum spontaneum sites in the Near East region.
Fig. 2. Distribution of Triticum boeoticum sites in the Near East region.
Fig. 3. Geographical distribution of Triticum urartu sites.
Fig. 4. Geographical distribution of Triticum dicoccoides sites.
Fig. 5. Geographical distribution of Triticum araraticum sites.
Fig. 6. Distribution of three Aegilops spp. sites in the Near East region.
As no wild hexaploid wheat has been found, bread wheat (Triticum aestivum L.; genomic constitution = AABBDD) probably originated from a cross of a cultivated tetraploid wheat and a goatgrass (Ae. tauschii) donor of its D genome. Recent evidence indicates that this may have happened in southwestern Caspian (Dvorák et al. 1997). Some diploid Aegilops species display a very characteristic pattern of geographical distribution (Fig. 6), which reflects their specific adaptation to different ecological zones. Presently, Ae. tauschii geographical distribution covers a very large area extending from central Syria in the west to China in the east. Nevertheless, the highest concentration of sites is in Transcaucasia, West Azerbaijan province of Iran and in the Caspian region of Iran. This might have been the original core of the species distribution, from which its weedy races spread with wheat and barley cultivation to the east and west. The genetic diversity data support the assumption that the southern or southwestern coast of the Caspian Sea might be the center of Ae. tauschii origin (Lubbers et al. 1991; Dvorák et al. 1997).
Both Ae. speltoides and Ae. searsii have been frequently suggested as donors of T. dicoccoides B genome. The geographical distribution and ecological adaptation of Ae. speltoides mostly coincides with that of T. boeoticum and both species may be the dominant components of grasslands on basaltic soils in southeastern Turkey. Ae. speltoides is also similar to boeoticum wheat in being absent in Jordan and in the Hauran region and Jebel Al Arab of southern Syria. Ae. searsii, another putative donor of the wild emmer B genome, is sympatric to T. urartu in Jordan, southern Syria and Lebanon and its geographical distribution and ecological niche are distinct from Ae. speltoides.
The current geographical distribution of the wild wheats and barley has a different pattern from that at the onset of agriculture. As cultivated wheat and its wild progenitors and/or ancestors are similar in their ecology, land cultivation resulted in habitat fragmentation and gradual habitat loss in large areas of the Near East. Moreover, the original habitat of wild cereals was also destroyed or modified by other detrimental activities related to human population growth in the Near East region. Therefore, the remaining wild cereal population sites are mostly disturbed and degraded by animal overgrazing. On the other hand, the current distribution area may be larger than 10,000 years ago, because the wild species were spread as admixture with seeds of cultivated species and some of them, like H. spontaneum, T. boeoticum, T. urartu and Ae. tauschii, developed weedy races, well adapted to growing in cereal fields. Consequently, diploid wheat species, T. boeoticum in particular, occupy a larger geographical area than tetraploid wheat species, T. dicoccoides and T. araraticum, which are not weedy.
The maps by Harlan and Zohary (1966), Johnson (1975), Zohary and Hopf (1988) and some others have already contributed to the discussion on the wheat and barley domestication. Nevertheless, the new data presented in this paper on the current geographical distribution of wild progenitors and close relatives of wheat and barley, two 'founder' crops of the Neolithic revolution, may still be useful in the discussion on the origins of agriculture in the Near East.
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A useful distinction when thinking about the events and processes in the past is the difference between history and prehistory (Barfield 1967). History encompasses those events that humans perceived and recorded either through writing or art, whereas events that humans may or may not have perceived, but did not record, fall into the realm of prehistory. This distinction places most of the events in plant and animal domestication and crop evolution in prehistory, which implies that there may be difficulty in knowing exactly what happened because these events took place such a long time ago and were not interpreted at the time by humans. When we think of in situ conservation of the wild relatives of our crop plants in relation to their history we should insert 'prehistory' into the title. Further, the word history in the title can have several different meanings, depending on whether we think of the history of the crop plant or the interaction of the plant with the history of humans.
Thinking of the prehistory and history of the plant in a genetic sense and taking durum wheat as an example, we believe that this wheat was selected from dicoccum or emmer wheat, which was domesticated from wild tetraploid populations of emmer, namely Triticum turgidum L., subsp. dicoccoides (Körn. ex Asch. & Graebn.) Thell. about 10,000 years ago (Zohary and Hopf 1993). Today there are still primary stands of wild emmer at various locations in the Fertile Crescent, and some of these should be conserved in situ. Populations I have seen include the extensive stands in the Jebel Druz in southern Syria, where the wild relative may also grow with diploid T. urartu Tum, ex Gand. On the drier eastern side of the Jebel Druz, T. urartu grows alone. A population should be conserved from northern Syria, possibly the Der Jamal site in Aleppo province. This population includes wild emmer (T. urartu) and wild einkorn [T. monococcum L. subsp. aegilopoides (Link.) Thell]. At a site near San Simeon monastery, Aleppo province, the other wild tetraploid wheat [T. timopheevii (Zhuk.) Zhuk. subsp. armeniacum (Jakuz.) van Slageren] is found, and this would be a prime area for in situ conservation. If wild tetraploid wheats are found growing in northeastern Syria, in Hassakeh province, that site should also be conserved. Lebanon has several populations of wild emmer worth conserving. These include that at Rashayya in the south Beka'a Valley, where wild emmer was first collected at the end of the 19th century, and there are several locations in oak-park forest habitats flanking the central Beka'a Valley, where primary populations of wild emmer appear to thrive. I stress the need to conserve primary populations in old established habitats rather than weedy secondary populations along roadsides, which may show a strong founder effect and exhibit little genetic polymorphism. An example of a secondary population in Aegilops speltoides Tausch. might be the roadside population northwest of the village of Abeen in Aleppo province, Syria, whereas a more primary population might be that at Ain Diwar in Hassakeh province (Waines et al. 1998). With reference to einkorn, we also need to preserve populations of wild einkorn from the extremities of its range, which extends from southeastern Europe to the Caucasus and south into Lebanon, Syria, Iraq and Iran, and northward into the Crimea.
Tetraploid wild emmer (BBAA) has its own evolutionary prehistory. This is currently interpreted as being the result of a cross between a wild diploid goatgrass (BB) similar to Ae. speltoides (SS), which was the female parent, with wild T. urartu (AA) as male parent (Dvorák and Zhang 1990). Hence primary populations of all three species need to be conserved in situ. However, the two diploid species and the derived hybrid allotetraploid occupy different habitats and have different ecological requirements, especially for minimum amounts of rainfall. For example, Ae. speltoides requires more precipitation than T. turgidum subsp. dicoccoides, whereas T. urartu extends farther into the drier areas than the other two species. Although we do not know what climatic conditions were like tens of thousands of years ago, the three species grow together only rarely today. The population between Kilis and Gaziantep in Gaziantep province, Turkey, is one that springs to mind. This population also has the other allotetraploid wheat species T. timopheevii subsp. armeniacum, which has a female parent genome designated (GG). This genome is also considered to have come from Ae. speltoides, perhaps at a later date than the (BB) genome. There are several translocation differences between the (BB) and (GG) genomes (Feldman 1966).
As Ae. speltoides was the female genome donor to both emmer and timopheevi wheats and provided the chloroplasts and mitochondria to the polyploid wheats, it has been argued that more effort should be made to conserve this species in situ, than either T. urartu or Ae. tauschii (DD) (Waines et al. 1997).
The DD genome of bread wheat is known to have been contributed by Ae. tauschii, a diploid goatgrass native from near Russafeh, Raqqa'a province, in the Syrian Desert to western China. A population is also known from the western side of the Ceylanpinar State Farm in Urfa province, Turkey. The annual precipitation at Russafeh averages 150 mm, but Ae. tauschii grows in cereal fields in depressions left by the meandering Firat River, so these areas may receive winter runoff, and the actual water available may be more. Aegilops tauschii is thought to confer ecological adaptability to bread wheat, which is more tolerant to drought, cold and heat than durum wheat, quite apart from genes for bread-making, and disease and pest resistance. Aegilops tauschii should be conserved in situ in these dry desert regions, as well as in wetter sites in northwestern Iran, where the actual parent of bread wheat may have grown (Dvorák et al., this volume).
Soil types and animal predators
Many wild cereal populations thrive in basalt soils or around piles of basalt rocks collected when fields are cleared. These rocks seem to protect the plants from grazing animals. Soil types are important for wild cereals, and populations that thrive on basalt, terra rosa, alluvial and possibly serpentine soils are known. The degree of soil cracking as fields dry out in summer is important, for spikelets and spikes can be protected in the cracks from predation by seed-harvesting ants, rodents and fire. There is little information from the Near East on the extent of predation by insects, animals and fungal diseases on fruits and seeds of wild relatives of cereal and legume crops. Nor do we have much information on overgrazing of wild cereal stands by sheep, goats and cattle. Harvester ants of the genus Messor may be important in gathering and disseminating wild cereal grains in specific areas of the Near East such as Israel and Syria. Rodents of unknown genera have been observed to harvest wild wheats and goatgrasses in Syria in the Jebel Druz and Jebel Abd-el-Aziz, respectively. At the latter site, Ae. crassa spikelets were collected and transported to threshing mounds. Clearly, harvester ants and small rodents may be a force that selects for wild wheat inflorescences that disarticulate at maturity. Larger rodents may harvest and select for goatgrass inflorescences that remain entire.
The agricultural system
History can also apply to the crop and the agricultural system in which it is farmed. An example is the areas of north-central Turkey where landraces of einkorn (T. monococcum subsp. monococcum) and emmer [T. turgidum subsp. dicoccum (Schrank) Thell.] wheats are still grown for animal and/or human food. The village of Sabace in Kastamonu province still grows landraces of these ancestral hulled wheats (Karagöz 1996; Nesbitt and Samuel 1996). Several villages in northern Morocco still grow einkorn wheats. We need ethnographic information on why these landraces are still grown, and we need to explore ways of preserving in situ the agricultural systems that include these landrace crops.
Endemic wild systems
Chickpea, Cicer arietinum, presents an interesting contrast to einkorn. As far as we know, chickpea was domesticated from wild C. arietinum L. subsp. reticulatum Ladiz., which has a very restricted area of distribution. It is known only from the provinces of Adiyaman, Mardin and Siirt, in southeastern Turkey and grows on limestone-derived soils (Zohary and Hopf 1993). A closely related species, C. echinospermum Davis, grows on basalt-derived soils in Urfa, Diyarbakir and Mardin provinces of southeastern Turkey and in the Jebel Sinjar in northern Iraq. Both species are able to exchange genetic material with C. arietinum subsp. arietinum, but in the case of C. echinospermum, there are some sterility barriers. Thus, the fourth most important pulse crop in the world, which has many landraces and modern cultivars in five continents, was domesticated from a wild species endemic to Turkey with a very small area of distribution. Surprisingly, although cultivated chickpea is so valuable a protein crop for humans, there appear to be no extant efforts to conserve wild populations in situ in southeastern Turkey. There is a need for the Turkish Government and IPGRI to develop a plan for in situ conservation of this valuable germplasm. Further, there appear to be few studies of the population biology of wild Cicer plants in its area of endemism; we do not know how extensive these wild populations are. I realize that these provinces in southeastern Turkey are politically unstable, but germplasm preservation of wild chickpea, the provider of 'hommous', is a subject that might find support from all people.
Widespread wild systems
Tepary bean, Phaseolus acutifolius A. Gray, affords a second example of a legume with a small area of domestication in a species with a wide distribution. Tepary grows wild from Arizona and west Texas south to northern Guatemala. There are two botanical varieties: acutifolius and tenuifolius. The former grows in valley bottoms, and the latter, with narrow leaves, grows on valley sides. The leaf and seed size characteristics are inherited. It is thought that the larger seed of var. acutifolius was that chosen by native Mexicans for domestication. All domesticated forms have a rare duplication of an enzyme locus, which only occurs in Sinaloa or Jalisco, Mexico (Garvin and Weeden 1994). This pinpoints domestication of tepary to probably a single act in Sinaloa or Jalisco, which spread later as a cultigen northward into Arizona and southward into Nicaragua. Wild populations in Sinaloa and Jalisco expressing the duplication should be conserved in situ, as should also populations from the extremities of the range of the wild species. In Arizona, many of the tenuifolius populations grow in the National Forest, so as long as the forest is protected, the wild teparies will be also.
Multiple sites of domestication
Common bean, Phaseolus vulgaris L., presents an interesting example of possible multiple locations and times of domestication (Gepts et al. 1986). Common bean grows wild from southern Sonora, Mexico, to northern Argentina. There are two subspecies: sylvestris in Mexico and Central America, and aborigineus in South America. These were domesticated in Mexico and South America, respectively, giving rise to the Mexican and South American genepools of domesticated common beans. It is possible that there was more than one domestication of wild beans in Mexico, giving rise to the Jalisco, Durango and other cultivated races from Mexico, all of which have distinguishing molecular and phenotypic characters (Singh et al. 1991). If this is the case, wild populations representative of all the domesticated races should be conserved in situ.
Forest trees were also important in the development of Near Eastern agriculture and civilization. In Lebanon there are one or two groves of the native cedar of Lebanon, Cedrus libani L. A sacred grove in Bsharri in the Lebanon Mountains is associated with a chapel. By preserving the cedar trees in this grove, other species are also conserved in situ, such as Secale montanum L., Vicia species and the beautiful, white-flowered ornamental Salvia microstegia. Sacred groves are common in forested areas in the Eastern Mediterranean countries and in other areas such as India and West Africa, and they may constitute small but important in situ conservation sites (Lebbie and Guries 1995; Nair et al. 1997).
Archaeological sites may also act as good in situ conservation areas. The dead Byzantine cities in northern Syria are important archaeologically. Some of the buildings are intact, others were toppled by earthquakes. Among the fallen stones, somewhat protected from grazing animals, grow many wild relatives of the Near Eastern complex of domesticates such as Pisum sativum L. subsp. humile Boiss and Noë and subsp. elatius Bieb., and the yellow-orange flowered P. fulvum Sibth and Sm., Lathyrus species, Vicia species, Lens species, as well as Hordeum vulgare L. subsp. spontaneum Koch, Aegilops, Triticum and Avena species. Several ornamental plants also inhabit these ruins, including wild black iris, which may have had a long association with humans because of their beauty or their association with cemeteries. Clearly protecting ruins also conserves the wild relatives of crop plants, as was suggested for relict cacti in Mexico (Bentz et al. 1997).
International borders and military bases
Other areas that can double as an in situ conservation site are international border zones. One most relevant is that between northern Syria and southern Turkey. Especially on the Turkish side, there is a strip of land of variable width that is retained as native vegetation, whereas other parts of the zone are farmed. The unfarmed areas may be mined. In the areas that have native vegetation, and which can be seen from the main road outside of the zone, T. urartu and T. monococcum subsp. aegilopoides appear to grow, and I assume that there are other relatives of crop plants.
The Herbarium at the University of California, Riverside, recently undertook a project on a nearby US Marine Corps base in the Mojave Desert to monitor the presence and food source of an endangered species of desert tortoise (Gopherus agassizi) which inhabits the base, despite the live shells that explode around it from target practice.
The military of great countries have a vested interest in protecting the natural resources of those countries, especially the relatives of their crops. There appears to be little disturbance to vegetation within the Turkish border zone. In areas rich in the relatives of crop plants, such as the Near East, these border zones can also be recognized to double as in situ conservation sites.
Agricultural research stations
A final example for in situ conservation sites of either native or introduced species is national or state agricultural experimental stations or state farms. The Ceylanpinar state farm in Urfa province, southeastern Turkey, is being developed as an in situ conservation area for wild cereals, legumes and other Near Eastern domesticates by the Turkish Government and the World Bank. This large state farm is located in the northern apex of the Fertile Crescent. The advantage of using state farms is that the state already controls the system of agriculture practised there.
In northern California, the Hopland Field Station in Mendocino County is part of the University of California Agricultural Experiment Station system. The Station is primarily used for rangeland experiments with sheep and other animal-plant interactions. In the 1950s, one field became infested with bearded goatgrass, Aegilops triuncialis L., and this noxious weed has now invaded most areas of the station. At Hopland, this aggressive tetraploid weed is successful because it appears to have no disease, insect or rodent predation. This allows for prolific regeneration and spread by this competitive wild wheat, which is the most widespread of the wheat genepool after durum and bread wheats. Such a situation allows for an excellent study site where the population ecology of this grass can be monitored without the interference that might be found in the Near East. Why are some tetraploid goatgrasses such aggressive weeds? To what extent does the unusual dissemination of the entire inflorescence contribute to this success? A similar mechanism with dissemination of multiple fruits or seeds is found in crops from other families, for example, Chenopodiaceae and Moraceae.
Another example of the usefulness of national agricultural experiment stations to study in situ conservation is found in Syria, where cooperation between the Syrian Department of Agriculture and ICARDA has set up study sites in four different ecogeographic areas in the country. The site at Yamuk Experiment Station near Azaz in Aleppo province has allowed for replicated experiments lasting several years, in which wild cereal and legume relatives can be studied in single-species plots or as interactions in multiple-species plots. Similar experiments have been set up at Tel Hadya, south of Aleppo, on a station near the Lebanese border, and on one in the Jebel Druz. There is a need for sites similar to the long-term Rothamsted Park Grass Experimental Field to study in situ conservation over many seasons, using many different members of the relatives of Near Eastern crop plants. There is also the ability to study controlled grazing or burning of these in situ sites to approximate more exactly the conditions in farmers' fields.
In Turkey and in Syria, experiments are underway to set up and study long-term in situ conservation sites for relatives of the Near Eastern complex of domesticated plants. At present, there is a shortage of basic information on population biology and ecology of the several plant and animal species that inhabit primary sites and potential locations for in situ conservation. Besides the interactions of wild plants and animals, we need to understand the interaction of these wild species and landraces with modern plant and animal agricultural systems. Considering the large sums that have been spent to understand biodiversity and population ecology of nonagricultural species, it is high time that funds be provided to understand the population biology and ecology of the ancestors of our major crop plants, many of which are native to the Near East.
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Waines, J.G., S. Hegde and J. Valkoun. 1998. Diversity in wild wheats from northern Syria. In Proc. Third Int. Triticeae Symp. IPGRI/ICARDA, Aleppo, Syria, May 4-8, 1997 (A. A. Jaradat, ed.) (in press).
Zohary, D. and M. Hopf. 1993. Domestication of Plants in the Old World: the Origin and Spread of Cultivated Plants in West Asia, Europe, and the Nile Valley. 2nd edition. Clarendon Press, Oxford, UK.
The evidence for domestication of plants goes back only 10,000 years and 8500 years for animals. Domestication is not an event but a process. Humans seem to have taken an immensely long time to discover the process of obtaining food through plant cultivation. Perhaps food was obtainable in abundance exclusively by hunting, gathering and fishing, hence no need was felt to explore the possibility of cultivation - a relatively more labor-intensive task.
According to a report in the London Times dated October 25, 1995 on the proceedings of a conference on 'Food, People and Health', a suggestion was made that humans should turn the clock back about 15,000 years and eat the diet of the hunter-gatherers in order to maintain good health. The late Palaeolithic diet included relatively lean meat of undomesticated animals, wild fruits and vegetables and nuts, berries and tubers with little or no cereals or dairy foods. It seems this diet matches human metabolic requirements perfectly. According to Professor Boyd Eaton (pers. comm.) communities changed over to agriculture to support a growing population and sustain larger social groups rather than to improve their diet.
The transition from hunting/gathering to agriculture
Smith (1976) suggests that the presence of abundant supplies of wild grains and other resources following favorable post-Pleistocene environmental changes could have led to a 'mini' population explosion in Southwest Asia. Increasingly sedentary lifestyle may have further accelerated population growth through closer spacing of births, a higher rate of infant survival, and perhaps a lower rate of adult mortality. Harlan (1992) maintains that hunter-gatherers have survived until today in places where agriculture is unrewarding.
Several crop plants which have assisted in the establishment of western civilization have their origin in an arc of land that connects the valleys of the Euphrates and the Tigris with the Jordan. This was termed the Fertile Crescent by Breasted (1938).
Besides the evolution of a non-brittle rachis which led to the domestication of wild cereals there is also the fact that persistent glumes made threshing difficult. At what stage after domestication did the cereal spikes develop into free-threshing types so that the grains could be easily obtained? Even today in some of the subsistence farming communities in West Asia and North Africa (WANA), the most primitive methods of separating grains from chaff are utilized such as repeated trampling of harvested stems by horses, mules or donkeys. Hence, it is probable that domestication took place in two stages. The selection for a non-brittle rachis was followed by selection for plants with free-threshing grains from spikelets. In fact, the two most ancient forms of wheats - einkorn and emmer - have persistent glumes on their grains. Their flour and dough properties are very different from those of macaroni wheat (Triticum durum) and bread wheat (T. aestivum) which evolved several centuries later (Nesbitt and Samuel 1996).
The ancient cereals (the term 'cereal' has its origin in the name of the Roman goddess of plenty: Ceres) such as tetraploid wheat and barley seem to have originated in or near the oak woodland belts in an arc through the hilly country surrounding the Syrian-Mesopotamian Plains (Harlan 1970) between 10,000 and 8000 BP (van Zeist 1969). The study of their domestication is facilitated by the fact that their wild progenitors can still be found in areas which Vavilov considered as their centers of origin (Damania 1990). In southeastern Turkey, northern Iraq and western Iran (part of the Fertile Crescent) wild wheats and barley are found in the oak forest belt. Archaeobotanical evidence indicates that wild plant species were present on human habitation sites at least 2000 years before the process of domestication began.
Very recent studies on einkorn wheat domestication using amplified fragment length polymorphism (AFLP) show that T. boeoticum was domesticated in southeast Turkey in the Karacadag Mountains close to Diyarbakir (Heun et al. 1997). However, localization of the precise domestication site of one 'founder crop' through DNA fingerprinting does not necessarily imply that the human hunter-gatherers living there at the end of the Palaeolithic period played a decisive role in establishing agriculture in the Near East. However, charred remains of wild einkorn found at sites on the middle Euphrates, such as Abu Hureyra and Tell Mureybit, downstream from the Turkish location in Syria may have evolved there independently since the climate at that time was conducive to their growth (Hillman 1996).
West Asia, and particularly Syria, has not only been a cradle of human civilization but also includes areas where domestication of wild plants may have first occurred (van Zeist and Bakker-Heeres 1982). By 7000 BP, both wheat and barley had spread to the Harsuna settlements of northern Iraq. The region includes two of the most important Vavilovian centers of origin of food crops - the Near East and the Mediterranean. These two regions fall within the pattern of global genetic diversity also described by Harlan (1970, 1971). The rich regional biodiversity in crop plants and their wild relatives is now threatened by rapid urbanization and overgrazing by small ruminants as flocks are multiplied to satisfy the demands of an increasing human population.
The Neolithic (= food-producing) agricultural development in West Asia depended primarily on the cultivation and subsequent domestication of three species: (1) einkorn wheat (Triticum monococcum) domesticated from its wild progenitor T. boeoticum, (2) emmer wheat (T. dicoccum) domesticated from T. dicoccoides, and (3) two-row barley (Hordeum vulgare subsp. disticum) from H. spontaneum. The domestication occurred with the unconscious selection by the early farmer for heads with a non-shattering rachis. The wild mode of seed dispersal gradually disappeared, the wild-type germination of seed on the ground was lost, and there was an increase in kernel size and yield potential (Diamond 1997). The plants which evolved with these traits subsequently lost their ability to survive in the wild.
Small fanning villages have been excavated in the Jordan Valley as well as near Damascus and along the middle Euphrates (Willcox 1996). Over the next 8000 years or so domesticated cereals would provide reliable food sources, thus eliminating the need for people to rely on the wild species that had defined human existence for thousands of years. Further, unlike before, the food grains could be stored for a number of seasons. This led to growth in human population as well as more complex human societies. Today 97% of arable land in WANA is under cultivation with a possibility that human population growth may overtake food production. Crop failures and famines are also an integral part of agricultural systems.
The wild progenitors of cereal crops
Wild einkorn (T. boeoticum) (2n=14) occurs across a wide area in the northern portion of the Fertile Crescent, through much of the Anatolian peninsula and penetrates into the southern Balkans. In addition, wild einkorn also occurs as a weed on the borders of cultivated fields and along roadsides. Two main ecogeographic races of T. boeoticum have been recognized by botanists. A relatively small one-seeded type typical of the cooler Balkans and Western Anatolia is usually referred to as T. boeoticum subsp. aegilopoides, while the larger two-seeded race in the warmer dry summer areas of southern Turkey, Iraq and Iran is commonly referred to as T. boeoticum subsp. thaoudar. In Anatolia all intergradations and intermediates between these two races occur often in mixed stands (Zohary 1969).
Wild einkorn was frequent among the plant remains found at Epipalaeolithic Abu Hureyra on the middle Euphrates and more recently by Willcox (1996) at D'jade. Further south at Tell Mureybit, also on the middle Euphrates, van Zeist and Bakker-Heeres (1984) of the Biological Archaeology Institute, Groningen, Netherlands found strong evidence of the extensive use of wild einkorn as a food source. Both Abu Hureyra and Tell Mureybit sites are now permanently under Lake Assad which flooded them about 20 years ago when the Tabqa dam was built. In 1970 Jack Harlan, in an experiment conducted at the University of Illinois, Urbana-Campaign, showed that a small family could gather enough wild einkorn in only three weeks of hand-harvesting to last a full year (Smith 1995).
Vallega (1996) speculates that T. boeoticum and other wild cereals were probably harvested prior to maturity to avoid losses due to brittleness of the rachis. The glumed grains may have been exposed to fire and roasted and eaten as whole kernels or ground into a meal of porridge or made into unleavened flat bread. Even today grains of free-threshing polyploid wheats are harvested while still green and roasted to produce 'frekeh' all over WANA.
Wild emmer (T. dicoccoides) is the progenitor of cultivated emmer (T. dicoccum). Both the wild ancestor and the domesticated form have a tetraploid configuration (2n=28), separated by a distinct seed-dispersal biology. Hybrids between them are fully interfertile, thus encouraging continuous gene exchange between the two. Wild emmer has a typical shattering rachis with each spikelet serving as a seed-dispersal unit, whereas in the domesticated emmer the mature ear stays intact and grains are separated from the spikelet only by vigorous threshing. The grains retain their persistent glumes unlike the more evolved T. durum, where the grains are naked. In spite of the availability of naked wheats, hulled wheats like emmer were preferred for several thousands of years until about 3000 BP (Harlan 1995). It remains a mystery why hulled wheats dominated over naked ones in several different cultures for a very long time, and in some cases continue to do so right up to the present day.
Hulled wheats were more successful because of their persistent glumes which prevented incidence of fungal diseases such as stem and yellow rusts, to which naked wheats must have been invariably susceptible (Nesbitt 1995). Also, they were ideal feed for poultry and domesticated animals. Furthermore, emmer has a higher protein content percentage (18.6-20.9%), a significantly higher number of total and fertile tillers producing a large biomass, and tolerates poor soil and adverse climatic conditions with little need for the use of fertilizers (Damania et al. 1992). But in recent years their area of cultivation is in steep decline, often being restricted to a single field in a mountainous village (Perrino and Hammer 1982).
Vavilov observed that emmer fields were cultivated by Armenians in Persia and by the Basques in Spain and that they were invariably infested with wild oats. Certain Italian farming communities in the Appennine Mountains, using traditional agricultural practices, still grow Triticum monococcum (einkorn) and T. dicoccum (emmer) wheats. They were extensively grown during Roman times but thought to have disappeared from the peninsula (Perrino and Hammer 1982). With support from the European Economic Community (EEC), efforts are being made to convince these small farming communities to continue to grow these hulled wheats.
Wild emmer has a more restricted distribution than wild einkorn. It is found in Israel, south Syria and Transjordan. Its center is on the slopes of eastern Galilee and the adjacent basaltic plateau of the Golan Heights and the Hauran Plains. In these areas T. dicoccoides is fairly common, particularly in places that are not overgrazed by small ruminants. Most recently samples have been discovered growing on basaltic soils in northern Syria, close to the border with Turkey. Robust, early maturing types are found growing in relatively warmer habitats and more slender, later-maturing types are found at higher elevations, e.g. on the eastern slopes of Mt. Hebron.
There is also another form of wild tetraploid wheat, T. araraticum, which is found in the former Soviet Transcaucasia, Syria, southeastern Turkey and Iraqi Kurdistan. While T. dicoccoides crosses easily with cultivated tetraploid wheats, T. araraticum does not, most probably because of the different genomic structure of their chromosomes. The latter shows close genetic affinity with the endemic T. timopheevi, a restricted and rare form of cultivated tetraploid wheat found in a single district of Georgia in the former Soviet Union (Zohary 1969). It is probably a more recent domesticate rather than an old relic crop plant from the past (Zohary 1996). Rapid diffusion of both einkorn and emmer wheats from the Fertile Crescent area preempted the widespread cultivation and diffusion of other related domesticated wild grasses, such as T. timopheevi (Diamond 1997). It is speculated that when emmer cultivation spread to Transcaucasia, local populations of T. araraticum could have grown as a weed of emmer crops and, by being incorporated into the agricultural cycle of harvest and sowing, became domesticated (Nesbitt and Samuel 1996).
Similarly, other lesser-known hexaploid wheat forms such as T. compactum or club wheat and T. spelta, T. vavilovii and T. macha were once grown in Central and West Asia and are found as single-plant volunteers in fields of durum and bread wheat even today. Another hexaploid wheat, T. sphaerococcum or shot wheat, originated in India but did not spread. Lesser-known tetraploid wheats such as T. polonicum, or Polish wheat, also have a restricted growth area.
Mention must be made here of a form of tetraploid wheat (Triticum turgidum) or poulard wheat which is still being grown in the Yemen although it is now rapidly being replaced by varieties of bread wheat mostly introduced from India (Damania et al. 1985). Poulard wheat could have been introduced into Yemen from Ethiopia, which is considered by some authors as a center of secondary diversity of tetraploid wheats. The hard poulard wheat samples collected in 1980 and 1981 from the Yemen by missions sponsored by the International Board for Plant Generic Resources (IBPGR) had a high gluten content and were distinguished from durum wheat (T. durum) by a pale brown seed color and larger kernel size (Damania 1983). Flour color probably excludes this form of wheat from being used extensively for pasta-making.
Wild barley, Hordeum spontaneum, the progenitor of cultivated barley, H. vulgare, shows a much wider distribution and over much more diverse types of terrain than wild wheats. The earliest carbonized remains found of cultivated barley are of the two-row type, but six-row morphology appears at Ali Kosh (in Iran) at around 8000 BP (Harlan 1995). Wild barley is found all over the Fertile Crescent where it forms an important annual component of open formations, and is particularly common in the dry-summer belt of the deciduous oak forests, east, north and west of the Syrian Desert and the Euphrates basin as well as the slopes facing the Jordan Rift Valley (Zohary 1969). In the Fertile Crescent countries H. spontaneum is often seen growing on the edges of cultivated fields and roadsides. It is rarely found at higher elevations since it does not tolerate cold very well but is more xeric than the wild wheats and can be found in drier areas of the steppes. Because of its shorter life cycle than wheat, barley can be grown on marginal areas of agriculture. There is abundance of diversity in forms from large-seeded, long-awned types to slender, small-seeded types. Intermediate forms between these extremes are found all over Israel, Syria, Turkey and Iran. Hillman and Davies (1992) and others have shown that low proportions of tough rachides (basal internodes) can occur in assemblages of wild barley and one has to be cautious in using their presence as an indicator of domestication.
In situ conservation of cereal wild progenitors
The ecological amplitude of wild relatives of the three founder cereals may exceed those of the crops derived from or related to them, a feature plant breeders exploit to enhance resistance to biotic or abiotic stresses, thereby increasing the adaptive range of the crop concerned.
Recent pilot studies carried out at ICARDA in Syria (Valkoun and Damania 1992) and elsewhere (Jana 1993) have demonstrated extensive genetic diversity in the original populations of the wild genepool in the natural habitat which is impossible to preserve by the standard ex situ collecting procedures. Also, it is generally accepted that during field collection usually only about 50 to 150 plants per site are sampled and many genotypes may be left out. On the other hand, under in situ conservation a much larger and continuously evolving genetic diversity is preserved.
Indirect evidence from studies carried out so far indicates that in situ methods should be effective for the conservation of genetic diversity in populations of both cultivated and wild species. During their long history of propagation in crop fields in the centers of origin and primary diversity, landrace populations of major crop species were in close association with their wild and weedy relatives. They occasionally exchanged genes, usually at the borders of cultivation, and mutually enriched their genetic diversity (Kuckuck and Pohlendt 1956). They coevolved, during which time they were exposed to a multitude of biotic and abiotic stress selection pressures to which they have adapted themselves as seen in bread wheat (Triticum aestivum) fields in Iran (Damania et al. 1993).
From biological considerations, the relative merit of the in situ method for conserving biodiversity within a cultivated species may be best evaluated in comparison with its wild evolutionary progenitor. Although several comparative studies on diversity in wild and cultivated barley have been reported (Jana 1993), comparable investigations are rare in wheat. In a preliminary assessment of genetic variation in durum wheat (Triticum durum) wild emmer (T. dicoccoides) populations from Turkey, the results showed that there was no difference in overall genetic diversity between the two.
Germplasm could be repeatedly collected from in situ conservation sites for offsite evaluations from time to time. The sites should be exposed to limited grazing periodically in order to maintain soil fertility and prevent it becoming a forest again. An ongoing experiment spanning five years is underway at ICARDA to establish well-defined populations of wild relatives of cereals and legumes conserved in situ and thereby determine the main factors which affect survival and competitive ability, and evaluate colonizing ability and regeneration capacity in populations of the target species: Hordeum spontaneum, Triticum urartu, T. boeoticum, T. dicoccoides, Lens orientalis, L. odemensis and two annual Medicago species and their mixtures. Sheep are allowed to lightly graze the experiments to simulate as far as possible the actual disturbance factors involved in this type of conservation effort.
In wild cereals such as T. boeoticum, T. dicoccoides and H. spontaneum, selection for a non-brittle rachis led to their domestication. Both wild diploid wheats and wild barley show great climatic tolerance in terms of their natural distribution. Their natural habitats range widely in latitude and altitude. Wild einkorn (T. boeoticum), for example, can be found growing from sea level in Macedonia to 2000 m asl in Iran and Iraq. The most dense stand encountered so far has been in southeastern Turkey at altitudes between 900 and 1500 m (Willcox 1992) in the Karacadag Mountain areas. Wild emmer (T. dicoccoides) has been reported from 100 m below sea level in the Jordan Valley and at 1500 m on the slopes of Mt. Hermon in Palestine (Zohary 1969). Several of these habitats qualify for consideration as in situ conservation sites.
During explorations in Iran, Damania et al. (1993) noted that the presence of wild Triticum taxa, in areas of their previously reported center of diversity, was extremely limited. This observation is worrisome, not only from the conservation point of view. Triticum species are a useful genetic resource since it has been reported that the wild species may provide valuable traits, such as disease resistance and stress tolerance, for wheat improvement. It is recommended that certain sites in Iran be considered for immediate in situ conservation to preserve the few remaining populations of wild Triticum spp. Later, selected genotypes from these populations can be multiplied and reintroduced in areas where they were found in abundance in the past.
Monitoring and sampling in situ conservation sites
Genetic diversity through the study of seed storage protein (gliadin) polymorphism was carried out on populations of H. spontaneum, T. urartu, T. boeoticum and T. dicoccoides collected from the southern provinces of Sweida and Damascus, the Anti-Lebanon Mountains, and the northern province of Aleppo during 1991, 1992 and 1993. Relatively high genetic diversity was found in populations collected from the high plateau in the province of Sweida, while populations found in valleys of the Anti-Lebanon Mountains showed lower diversity (Valkoun and Damania 1992). The discovery of T. urartu growing in close proximity with T. dicoccoides and H. spontaneum in the middle of the Hauran Plain forms a link between the T. urartu populations found on the slopes of Mt. Hermon and the Jebel Al Arab Mountains of the Sweida province in southern Syria. This may also indicate that the Hauran Plain used to be the natural habitat of the two wheat ancestors and wild progenitor of cultivated barley before the area came under cultivation and was intensively grazed by sheep and other small ruminants. These wild progenitors could have been even more widespread than today during the Neolithic and there may have been a considerable time lapse between their usage as a food source, i.e. beginnings of cultivation and their actual morphological domestication (Willcox 1996).
Long-term monitoring of biodiversity is essential to develop an understanding of its value for conservation and sustainable use. During 1993 a monitoring trip was conducted jointly with Syrian scientists with the objective of gathering information on these sites (land use, farming system and socioeconomic background, botanical composition of the associated vegetation, etc.), and the target species populations (phenology, reproductive ability, vigor and health). It was observed that the populations of wild progenitors of cereals are relatively well protected from grazing during the vegetative phase when they grow on non-arable habitat among the basaltic rocks. They are inaccessible before the harvest of durum wheat by which time the spikes have matured and shattered on the ground, averting damage from grazing small ruminants. However, when the ownership of the land is not in private hands, flocks belonging to wandering Bedouin tribes graze continuously with deleterious effect on the plants. Only highly unpalatable spiny weeds survive this form of grazing and not a single plant of wild Triticum spp. is left standing (Damania 1994).
During these missions T. urartu populations were also sampled from the Anti-Lebanon Mountains growing on the borders of orchards, above the summer resort town of Bloudan, at an elevation of 1840 m asl, the highest collecting site reported for this species so far (ICARDA 1995). Studies on heat and cold tolerance in wild and obsolete wheat forms by Damania et al. (1993) revealed that T. dicoccoides was most susceptible to heat as well as cold. Among the diploids, T. urartu was significantly more cold tolerant than T. boeoticum, indicating perhaps the reason that the former can still be found at high altitudes in its center of diversity. Results of these studies are being used to identify the most suitable populations and sites and to develop a sustainable strategy, together with the appropriate land-management system, for in situ conservation of the indigenous wild wheat progenitors in Syria and the neighboring countries and adjoining territories.
With the initial support of the USDA, a project for in situ conservation of T. dicoccoides populations has been underway in Eastern Galilee in Israel for almost a decade. Between 1984 and 1989, individual plants were monitored at closely spaced permanent sampling points along with four topographically diverse transacts. Collections of single spikes were made annually from these plants and seed from progenies were sent for ex situ conservation. The 1-ha site is located 1 km west of Kibbutz Ammiad, in a hilly tract that is the southern extension of the Mt. Kenaan ridge. The in situ conservation site so established would protect and maintain the entire genepool of the selected populations. The climate is typical mediterranean with an average rainfall of 580 mm which falls during the winter months. As in Syria, the survival of these populations of wild wheat progenitors is now increasingly threatened by human population pressures and intensified mechanical agricultural practices of the settlers (Anikster and Noy-Meir 1991).
Some of the problems in areas of in situ conservation of wild species have been highlighted by results of the Ammiad experiments. One of the most difficult decisions of all in the establishment of such reserves is to determine the size of its area. The minimum viable population size will be greater than the minimum effective population size of individuals that can contribute to the next generation. During the last four years, the wild wheat study using the Ammiad methods of sampling and progeny testing has been extended to other wild populations, particularly in two nature reserves in Yahudiya, an area located in the Golan Heights, and Har Meiron in Upper Galilee (Anikster et al. 1997).
In situ conservation of wild wheat relatives at the Erebuni Nature Reserve, northeast of Yerevan in Armenia, has met with some success. Vavilov (1951) first recommended protection of this site because of its unique richness of the wider Triticum genepool. Triticum urartu was discovered there in 1935 by Tumanyan and later this species was fully described by Gandilyan (1972). Other wild wheat species, such as T. boeoticum and T. araraticum, grow in the protected area together with Aegilops spp. Amblyopyrum muticum, a species considered to be taxonomically intermediate between Aegilops and Agropyron, was also found near this nature reserve. Hence, this site in Armenia is the only site outside Turkey where the uncommon species of the Anatolian highlands are found. The actual size of the reserve is about 100 ha but protection of a much wider area, about 400 ha, is needed in order to include rare populations of other species growing on the periphery of the protected area as well as to provide a buffer zone for the protection of the core area.
The need to encourage in situ conservation of landraces in the communities in which they occur has been advocated by several authors (Altieri and Merrick 1987; Brush 1995; Peña-Chocarro 1996). Qualset et al. (1997) caution that it is a challenge to undertake in situ conservation of indigenously developed germplasm without a return to or preservation of obsolete agricultural practices which may be unacceptable or impracticable under sociopolitical systems in areas where diversity abounds. Besides, conservation of germplasm of an economically important crop in situ would most probably also result in the conservation of associated species occurring naturally in the same ecosystem. In situ conservation also permits natural evolution to continue, an extremely important option for the preservation of genes for abiotic and biotic stress resistance as species coevolve with their pathogens and changing environment.
In situ methods of conservation of landraces and wild progenitors are, understandably, viewed skeptically by plant breeders. As long as genetic conservation and crop improvement are directly linked, any form of conservation will be judged by its short-term benefits to breeders, and in situ methods will attract considerable criticism (Brush 1991). On-site conservation is more plausible if these two goals are decoupled, making biodiversity conservation an end in its own right. In fact, Jana (1993) has said that we should get away from the notion that in situ conservation of biodiversity of wild progenitors and landraces is only for safeguarding breeding materials for the future. Conservation should be practised for its own sake; it keeps the landscape green, enhances the quality of life and ensures the continuation of the ecosystem, and thereby the wellbeing of humankind.
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