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Published in Issue No. 131, page 1 to 6 - (22063) characters

Avena strigosa in Denmark and Lithuania: prospects for in situ conservation

Jens Weibull  Louis Lyng Johansen Bojensen  Valerijus Rasomavicius  Introduction
Bristle, sand or small oat, Avena strigosa Schreb. (sensu lato), is an annual diploid (2n=2x=14) species that includes both wild and cultivated forms. While the wild forms include the taxonomic species A. atlantica B.R. Baum & Fedak sp. Nov., A. hirtula Lag., A. lusitanica (Tab. Mor.) B.R. Baum Comb. Nov. et Stat. Nov., and A. wiestii Steud., the cultivated forms are comprised of A. brevis Roth, A. nuda L. and A. hispanica Ard. (Ladizinsky 1989; Leggett 1992). All these forms are interfertile but crosses with A. sativa are difficult. Several barriers to interspecific gene transfer must be overcome to bring genes of interest from diploid species such as A. strigosa to A. sativa (Forsberg and Shands 1969). Bristle oat has been considered an important source of resistance to crown rust (Puccinia coronata f.sp. avenae) and a number genes for resistance to crown rust have been reported.1 Other representatives within the A. strigosa group exhibit characteristics valuable for modern crop production such as resistance to other diseases-smut (Ustilago spp.) and powdery mildew (Blumeria graminis f. sp. avenae, formerly Erysiphe graminis f.sp. avenae) (Hall and Troke 1948; Griffiths 1962; Herrmann and Roderick 1996) or as an alternative fodder crop for hay production. It also does well under more extensive cropping conditions. Quality properties include high content of proteins and fat (Griffiths 1962). In Australia and also in South America the bristle oat variety SAIA is recommended as suitable for hay production.
Distribution in Europe
The area of origin and distribution of A. strigosa (sensu stricto) embraces most of West and Central Europe (Figure 1) and, at least historically, also ranged into the Nordic countries. The strigosa group, however, is also found in the vast area from the Iberian Peninsula—regarded as the centre of origin and distribution—to the plains of Afghanistan, occupying a range of ecological niches. Historically it has mainly played a role as a weed species in cereal fields but was grown for feed and fodder in the old Celtic cultures in west Scotland and the Hebrides (Körnick; cited in Thellung 1911). The species has also been reported from archaeological findings (Dickson 1996).
Most of the grown oats in Great Britain and Ireland until the 17th century was A. strigosa (Hunter 1924). Findlay (1956) reported that bristle oat was grown commonly in Scotland, not least due to its tolerance to acid soils, and is still being cultivated in some of the West Scottish isles (M. Leggett, pers. comm.). During the 1930s some breeding efforts on bristle oat were made in Great Britain (Hall and Troke 1948; Griffiths 1962) and two varieties were developed at the Welsh Plant Breeding Station in Aberystwyth. One of these, S.75, was still being grown for horse feed in parts of Cardiganshire, Wales according to Chater (1993). Carvalho de Vasconcellos (1935) described 14 varieties of A. strigosa cultivated in Portugal. As far as we are aware there is no evidence of any other breeding efforts in Europe. However, A. strigosa remained popular particularly in some mountainous regions. In the Karpaty bristle oat was cultivated until 1980 as feed crop for horses and pigs.
During the last 20 years, however, several authors have regarded bristle oat as a disappearing species. Kropá… (1981) concluded that A. strigosa was on the verge of extinction in former Czechoslovakia and Frey (1989, 1991) followed this up by providing information from Poland and other parts of Europe. His review, however, was generally based upon old herbarium material and many of the reported places of findings have long since been devoid of bristle oat. Podyma (1993), reviewing the European collections (altogether 232 entries) of A. strigosa, concluded that, since several countries were under-represented (e.g. the Nordic ones), new collecting initiatives were essential. He also noted that this synanthropic species, although historically important as a crop and weed in Poland, nowadays seemed to be disappearing owing to the changing agricultural practices. Korniak (1997), however, reported new findings from northeastern Poland and argued that in some areas the species was again increasing.
Meanwhile, the status of A. strigosa in other parts of Northern Europe has also rapidly deteriorated. In Denmark, where the species was historically grown for feed and fodder (Pedersen 1974; Løjtnant and Worsøe 1978), very few recent findings have been reported. In Sweden and Finland it is most likely extinct (Suominen 1979; Nilsson and Gustafsson 1982). The last reported finding of bristle oat as a weed in Norway was in 1941 (Høiland 1993). Ingelög et al. (1993) reported that the Mecklenburg-Vorpommern was the only stronghold around the Baltic Sea, although later findings in Lithuania showed that a few populations persisted in the southern parts of the country.
Taken together, these recent observations led the Nordic Gene Bank (Alnarp, Sweden) to initiate a project to look for the species at its historic localities in Denmark and to intensify the search for A. strigosa in Lithuania. Being an important genetic resource for plant breeding (earliness and stress resistance) it is regarded as an important species for Nordic conditions, mandatory to maintain in ex situ collections. At present, only four accessions have been deposited at the Nordic Gene Bank, only two of which have documented Nordic origins.
Materials and methods
Denmark
During the summer of 2000 most of north and west Jutland (W Denmark), including Lolland and parts of Sealand, was scrutinized for new localities for A. strigosa. These areas represent the historical stronghold of the species in Denmark. Altogether 4000 km were covered by car and, with an overall mean of five fields per kilometre, roughly 20 000 arable fields were subjected to the inventory. The total agricultural area of Denmark is about 2.64 million hectares. If every searched field is considered equivalent to 1 ha, then altogether 20 000 ha were studied or 0.8% of the total arable land.
The work followed two approaches: (1) assembling information about A. strigosa through herbaria, literature studies or via personal contacts; and (2) fieldwork. The latter, comprising surveys of suitable arable land, ruderal areas and fallows, was most intensive during the period from May until the beginning of August and included not only general surveys but also interviews with farmers.
Lithuania
Relevant Lithuanian publications were initially reviewed from the point of historical background data on the distribution of A. strigosa. At the same time herbarium specimens were investigated at the herbaria of the Institute of Botany (BILAS) and of Vilnius University (WI) in Vilnius, as well as at the herbarium of Nature Reserves and Ecological Education Station in Marijampole. Specimens held at the herbaria of other scientific institutions as well as private collections were also reviewed.
Fieldwork was carried out during the period June to September 2000 and the area of investigation covered the whole territory of Lithuania. The total distance covered exceeded 4000 km. About 2300 fields of various sizes planted with oat, barley or mixed oat-barley, and summer wheat crops were investigated. Special attention was paid to localities where:
1. according to the literature and herbarium specimens, A. strigosa had been encountered (Kaunas, Ukmerge, Šven…ioneliai, Zarasai, Plunge, Seda, Alytus);
2. oat traditionally is the main cultivated cereal (western, southern and southeastern regions of Lithuania);
3. environmental conditions are similar to those of Poland where A. strigosa still is rather common (regions adjacent to Poland in the southwest of Lithuania);
4. areas untouched by reclamation of land and where secluded farmsteads are numerous (wooded lands in the southeastern, eastern and western parts of Lithuania, as well as national park territories, etc.).
The sites in which A. strigosa was encountered were described as follows: the exact location by latitude/longitude of the field was determined using a GPS unit; approximate dimensions of the field were measured and the owner of the field was ascertained if possible. The sites were furthermore marked on the maps. The main characteristics of the agro-community where the species occurred were described, including total cover of cultivated crops (in %), abundance and coverage of A. strigosa (according to Braun-Blanquet coverage scale; Braun-Blanquet 1964), and presence of other dominant weeds. Herbarium specimens were also collected. Optionally, the owners of fields were questioned in order to obtain information on the history of the fields and the origin of the seed.
Results
Areas surveyed in Denmark are indicated in Figure 2. Despite an alleged report from Lolland in 1997 no findings were made. Samples suspected to be A. strigosa were checked but all were found to be A. fatua. Furthermore, none of the interrogated farmers had made any recent observations of bristle oat. There is therefore reason to believe that the species has disappeared from its last Nordic area of distribution or is on the verge of extinction.
Inventories in Lithuania, on the other hand, were more successful. Four new populations were discovered in the Eastern part of the country and more specifically within the Aukštaitija national park (Šven…ionys district; Table 1; Figure 3). One of these was very rich (coverage 3 on the Braun-Blanquet scale) and measured 3000 m2. As the localities are all situated within villages where extensive agriculture is practised there is reasonably good hope that the populations will prevail. Earlier known populations in the southern parts of the country (Alytus district), however, were seemingly extinct after the landowner had recently changed his seed. This shows that A. strigosa is (1) extremely sensitive to changing agricultural practices, and (2) does not appear to survive through a seed reserve but has to be replanted annually together with the crop.
Discussion
Bristle oat was being searched for in suitable habitats of most of its previous area of distribution in Denmark. Despite the extended field season and the many investigated farmer’s fields the total area actually searched was not more than 0.8% of the total agricultural acreage in the country. The large number of interviews, however, enlarged the actual area covered. In spite of these efforts no single specimen was located which indicates that the species does appear to be on the verge of extinction in Denmark, if it has not already disappeared.
During recent years very few findings of bristle oat have been reported in the course of completing the Atlas Flora Danica, i.e. the review of the national Danish flora. There can be many reasons for this. First, from an agricultural or weed point of view the species has been of much less importance than wild oat (A. fatua). We assume that very few people have actually been able to identify the species and we furthermore suspect that individuals of the species may have been mistaken for wild oat. This is supported by the fact that neither the Danish Plant Directorate nor the Danish Agricultural Advisory Centre had any information at all regarding its recent distribution or occurrence. Second, being a low-yielding species its importance as a crop has dwindled rapidly in modern agriculture. The last known bristle oat crops to have been harvested was in 1820 (Løjtnant and Worsøe 1978). Third, from a conservation perspective bristle oat has perhaps not been as attractive as other more conspicuous threatened species.
Several factors, most of them associated with modern agriculture, may explain the disappearance of bristle oat in Denmark. With the advent of modern technology the number of horses needed in agriculture was dramatically reduced which in turn had an effect on the cropped area of oats. Consequently bristle oat as a weed decreased simultaneously. Furthermore, improved seed cleaning effectively removed any bristle oat seed and thus prevented it from being re-circulated into the fields. As shown by Barralis (1965) A. strigosa lacks seed dormancy, a trait that drastically reduces seed survival in the soil, thereby preventing the species from building up seed reserves. Finally, it is likely that the intensified control of wild oat (A. fatua) during the second half of the last century helped in eradicating bristle oat as well. To summarize, we cannot completely rule out that bristle oat may still prevail in Denmark. There are documented findings from 1990 but the chance that populations may still exist in the country seems highly unlikely.
Fortunately, the situation appears to be slightly different in Lithuania. In the “Flora of Lithuania” (Natkevi…aite-Ivanauskiene 1963) bristle oat was considered to be a rather common weed in fields of spring-sown cereals. Two recent historical events, however, suggest that the basis for that observation perhaps had changed. First, in the course of farmland collectivization during the Soviet period, crop production was streamlined and intensified. Only officially approved varieties were allowed to be planted. Second, following the re-independence in 1990 a process of returning farmland to the former owners began and as a result of this, the intensity of farming dropped rapidly. Additionally, unfavourable agro-economic policies together with controversies regarding land properties left large areas under fallow.
As reported, the investigations during 2000 were successful in finding four new localities for A. strigosa in the country, one of which was indeed very rich. All new localities share the same characteristics: these are small, privately owned and extensively managed farms on poor sandy soils, where fields are tilled with horsepower and the weeds are fought mechanically. Crops are exclusively sown with uncleaned farmer-saved seed.
For the time being the survival of the bristle oat populations in east Lithuania depends on the will of the landowners. This is a vulnerable situation, however, as many of these are elderly and furthermore subject to an unfavourable agro-economic system. As the country is likely to change its current policies in the near future it is our belief that only special means, and directed support, will help in managing the remaining bristle oat populations.
In situ conservation in Europe
Most conservation activities in Europe today focus on managing genetic material ex situ, i.e. maintaining genetic resources away from their original growing sites. This is the situation for all seed material kept in genebank freezers or in field collections of vegetatively propagated species such as apples, onions and rhubarb to mention a few. Ex situ conservation also includes in vitro conservation methods that are common for crops like potato, some ornamental plants and small berries.
The Convention on Biological Diversity (1992), however, specifically points out the complementarity between ex situ and in situ approaches, and stresses the need for in situ programmes to be developed. The International Plant Genetic Resources Institute (IPGRI) recently launched a global in situ program (Jarvis and Hodgson 1998) aimed at improving conservation strategies worldwide. The work is being carried out specifically in regions rich in landraces and locally adapted material, but poor in financial resources.
Recently the European Co-operative Programme for Crop Genetic Resources Networks (ECP/GR) launched an initiative to begin in situ and on-farm conservation activities in this part of the world (Laliberté et al. 2000). The initiative not only addresses the need for conserving old and redundant varieties and landraces but also puts the conservation of wild crop relatives in focus. This process, together with a number of EU regulations (Table 2) aiming at improving the situation for biodiversity and marginal agricultural areas, is providing a solid foundation for developing conservation strategies.
The area of Švencionys in east Lithuania represents a suitable site for carrying out detailed studies on on-farm conservation of a wild crop relative. For sustainable management of the discovered bristle oat populations we need to answer a number of questions relating to the life cycle history of the species at this site, including changes in population size and structure. We need to determine the minimum population sizes necessary for sustainable conservation as well as study the influence of sowing and harvesting practices. In this respect all available traditional knowledge should be documented. Finally, this historically and geographically isolated bristle oat population could serve as an interesting object of genetic studies.
We are convinced that a prerequisite for A. strigosa surviving in our agro-ecosystems is the presence of small, extensively managed and private farms. This ‘agriculture at the margin’ will, in the long run, only be able to survive through external support from public funding. Safeguarding these niches for the sake of genetic resources conservation and the diversity of agriculture can be accomplished at relatively low cost. We will not be thanked by future generations if we let go of this opportunity.
Acknowledgements
The authors are grateful to Dr M. Leggett for reviewing the manuscript and to Koeltz Scientific Books for permission to reprint the world distribution map of Avena strigosa.
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