Schriften zu Genetischen Ressourcen - Genres

R. V. BOTHMER, TH. V. HINTUM, H. KNÜPFFER and K. SATO
The tendency of genetic erosion is, however, not conclusive. Also in the above mentioned
study by GRANER et al. (2002) some modern varieties actually showed an increased
diversity in some of the markers as compared to the foundation lines. Similar
results were reported on Nordic and Baltic material by KOLODINSKA et al. (2001)
based on inter-SSR and by MANNINEN and NISSILÄ (1997) based on RAPDs.
In areas where older and newer material is grown together, introgression and sowing
seed kept by farmers may pertain and even increase diversity. Such is the situation
on Sardinia where the common and variable landrace (’S’orgiu sardu’), grown over
the entire island for a long time shows evidence of having obtained genes from earlier
cultivated, more advanced varieties (PAPA et al. 1998).
In many areas a few barley cultivars can be dominating in time and space. So, for
example, is the Turkish cultivar ’Tokak’, released already in 1937, grown annually
over three million hectares for many years. The Russian cultivar ’Moskovsky 121’,
released in 1977 is grown annually over 2 million hectares since then (FISCHBECK
2002). This trend increases the vulnerability and decreases the diversity. If the trend
of large acreage over many years is kept too long it will drastically influence the replacement
of cultivars and the use of higher number of cultivars per acreage. This
will add to the genetic erosion. There may be several reasons for the genetic erosion
in barley (FISCHBECK 1992):
• The limited number of landraces used to select superior genotypes during the
initial phase of breeding;
• a small number of outstanding cultivars used as progenitors in breeding programmes;
• limited use of exotic germplasm.
Future development of diversity in barley
Barley is well represented in the world’s genebanks with ca. 378,000 accessions reported
(HINTUM 2002). However, duplications are common and of the reported number
it is at present not possible to estimate the actual number of unique accessions.
Moreover, due to the lack of overview we can neither indicate the “white spots” in
current holdings, i.e. from which areas or of which types no or restricted material is
available and which are in urgent need for intensified collecting or monitoring.
Currently, despite that there has been and still is an ongoing genetic erosion, it is not
known how large (or important) this is. It is also amazing that there is still variation
left in advanced material, and new genotypes can be obtained by crossing closely
related elite lines. This techniques has been used for more than 100 years and one
133