Integration of Conservation Strategies of Plant Genetic ... - Genres

K. Ham m er
Another factor for estimating the amount of plant genetic resourcesTable
6: Number of accessions
is the infraspecific variation, particularly of old and important cropsevaluated
in the Gatersleben
with a wide geographical amplitude. Some results from thegenebank
1975-1990
Gatersleben school of taxonomists have been compiled by Hammer
(1981) and are shown in table 9. These results are based on
Group
morphological traits but they provide a certain impression on the
No. accessions
wealth of infraspecific variation.
Cereals
44.548
Pulses
16.221
As a third factor the genepool has to be mentioned. When HarlanVegetables
3.557
and De Wet (1971) published their concept it was rather difficult toTotal
include the secondary genepool in breeding work. Today we known
numerous examples involving even the tertiary genepool and the
range of usable material became rather high (see e.g. von Bothmer Source: Hammer (1993b)
et al. 1992).
64.326
In this way maintaining and use of plant genetic resources is ever
more becoming a global problem, approaching to and merging withTable
7: Released cultivars bred
the efforts trying to manage biodiversity. This task calls for theusing
accessions from the
inclusion of a whole range of possible inputs in a concerted actionGatersleben
genebank (1973-
1990)
including the formal as well as the informal sector.
Crop No. cultivars
Ongoing evolution
Spring barley
30
Winter barley
Ongoing evolution within the populations of a genebank is a serious
Spring wheat
problem (see Hammer 1993a). Vavilov recommended theWinter
wheat
reproduction under ecologically and climatically similar situations asPeas
3
1
12
9
the collecting sites and created a net of stations all over the former Lettuce
1
Soviet Union. Other genebanks without such tremendous
Total
possibilities had to rely on line-splitting to avoid the loss of rare and
non-adapted genotypes within populations (Lehmann and Mansfeld
1957). Genebanks try to maintain the original variation particularlySource:
Hammer (1993b)
by effective methods of long term storage of seeds. In this way they
56
try to reach a static equilibrium. Whereas a dynamic equilibrium, including also the important hostparasite-interactions,
can be only achieved under on farm conditions.
The most spectacular cases of ongoing evolution under farm conditions are connected with
introgressions. Therefore, in many cases not only are on farm conditions involved but also more
generally in situ situations when wild plants (progenitors, related races) are included (Hawkes 1991).
In the following some recent examples for introgressions are mentioned. Introgressions have been
observed by us between
- wild (Secale strictum) and cultivated rye (S. cereale) in southern Italy (Hammer et al. 1985a);
- wild/weedy (Hordeum vulgare subsp. spontaneum) and cultivated barley (H. vulgare) in Libya
(Hammer et al. 1985b);