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The USDA Agricultural Research Service-managed National Plant Germplasm System (NPGS) coordinated several germplasm expeditions in the trans-Caucasus countries of Armenia, Azerbaijan, and Georgia beginning in 2001. One of the goals was to preserve valuable wild relatives of crop species ex situ at genebanks in the host countries and in NPGS genebanks in the United States. The Caucasus region is a center of origin for several important temperate fruit and nut crops that are conserved at NPGS facilities in Oregon, New York and California. Seeds and cuttings of landrace cultivars and wild relatives were collected from diverse habitats in accordance with international agreements and national laws. Since 2001, more than 50 unique accessions of Corylus (hazelnut), 20 Cydonia (quince), 23 Mespilus (medlar), 52 Pyrus (pear) and smaller numbers Amelanchier, Crataegus and Sorbus from these three trans-Caucasus nations have been added to the NPGS collections in Corvallis, Oregon. Almost 50 Ficus samples, 125 Juglans, 53 Pistacia, 50 Punica, 70 Vitis and many accessions of various Prunus species went to the genebank in Davis, California. Malus (apple) samples numbered 30 and were deposited at the genebank in Geneva, New York. Established accessions are evaluated for horticultural traits, environmental adaptations and pest resistance, and made available to researchers world-wide for genetic studies and crop improvement.

Fire blight in Bulgaria and Erwinia amylovora strains were subjects of field observations and laboratory tests within a 21-year period (1989-2009). Results from the most comprehensive survey for the country determined that fire blight is widely spread and the pathogen was found in 370 localities representing all administrative districts. The pathogen was isolated from 433 samples originating from 11 rosaceous host species: quince, pear, apple, Mespilus germanica (medlar), Crataegus monogyna, Pyrus sp., P. pyraster, P. elaeagrifolia, Amelanchier sp., Cotoneaster dammeri and Pyracantha coccinea. The cultural, physiological and biochemical characteristics of more than 370 preserved strains corresponded to the available data on E. amylovora (incl. API 20E and FAME profiles). Exopolysaccharide production differed among the tested strains, corresponded to virulence, and was particularly high for one strain from (225/12, = BG 16). Numerous DNA tests (23S rDNA, nested PCR, ams-PCR) revealed the existence of E. amylovora-related amplicons and genomic variability (SSR) among the Bulgarian strains as well. Streptomycin resistance (100 ppm) was not observed either during laboratory tests of plant samples or in isolates obtained afterwards.

To check the true hybrid character of seedlings, resulting from interspecific and intergeneric hybridizations in Malus × domestica, we have chosen macrosatellites (SSRs) as molecular markers since SSR loci are highly conserved among species and genera and because SSR primer information is available in cultivated apple. To study the transferability of apple SSRs to other species or genera of potential breeding parents within the Maloideae we screened 147 accessions of the Maloideae. These 147 accession covered 10 genera, with several representative species within each genus: Amelanchier (9 accessions), Aronia (5), Chaenomeles (8), Cotoneaster (11), Crataegus (9), Cydonia (11), Malus (20), Mespilus (10), Pyrus (47) and Sorbus (16). In total we tested 31 Malus × domestica SSR loci on each accession. We considered a marker as transferable when a successful amplification was obtained in at least 75% of the tested accessions. The transferability from cultivated apple to other genera and Malus species varied between 58% (Pyrus) and 94% (Malus). The mean number of alleles per (transferable) locus ranged from 1.9 (Cydonia) and 2.2 (Mespilus) to 11.5 (Malus) and 12.5 (Pyrus). The low allele diversity of a locus of Cydonia and Mespilus reflects most likely their apomictic behavior. Considering the transferability of the primer combinations from M. domestica to other genera substantial differences were found among microsatellites: from 0% to 100%, but for most of the primer combinations the transferability of a microsatellite marker was higher than 70%. The highest number of alleles over all species and genera of a specific locus was 62, the lowest only 5. In the latter case the primer combination of this locus amplified just one allele in most species.