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The level of genetic relatedness of ninety-six strawberry cultivars, released in dif­ferent breeding centres of seventeen countries, was estimated based on analysis of their DNA polymorphism. Five hundred fifty-eight polymorphic amplicons, with a size range from 80 to 2600 bp, were generated in PCRs carried out on the template of DNA isolated from plants representing all analyzed cultivars. In RAPD reactions, polymorphic bands covered 58% of the total number of PCR products, while in ISSR, SSR and selective AFLP, the polymorphic DNA fragments covered 75%, 70% and 67% of all amplicons, respectively. Data concerning DNA polymorphism were as­sembled using the PCo-A method (Principal Component Analysis), and then referred to information about country of origin and pedigree described by the breeders. The results showed that contemporary breeding uses genetic resources in a very narrow range. Consequently, the cultivars released in individual breeding centres presented a very close relationship and were grouped in one, or at most two, genetic clusters.
Experimental infection of Alstroemeria seedlings with naturally infected lily ‘Casablanca’ with stunting and flower bud deficiency phytoplasma resulted 3–4 weeks after top grafting in chlorotic and/or necrotic stripes, whitening of the leaves, shoot necrosis and die back. Flower discoloration or malformation were not observed. Attempts to transmit phytoplasma from naturally infected lily and experimentally infected Alstroemeria to Catharanthus roseus by top grafting resulted in stunted growth, dull yellowing and malformation of the leaves in 4–6 weeks. Some plants were temporary entirely vegetative and did not produce flowers. The periwinkle plants that were bridged by Cuscuta odorata from the diseased lilies and Alstroemerias showed similar symptoms as top-grafted ones. With the universal primer pairs rU3/fU5 specific PCR product with expected length ∼900 was amplified from samples collected from lilies with severe symptoms and top grafted test plants. All PCR products used for RFLP analysis after digestion with Alu I showed the same restriction profiles. Position of three obtained bands corresponded to the lengths of the DNA fragments of American aster yellows (AAY) phytoplasma group.
Three SCAR and two SSR molecular markers located on Lg 3 and Lg7 were used for early selection of apple genotypes. The purpose of the selection was to find a potential donor for resistance to fire blight (FB) in an apple breeding programme. This study was carried out on 35 breeding clones, and registered cultivars originating from seven countries. They were all characterized as having different levels of sus­ceptibility to FB in field conditions. The number of generated markers varied from 1-2 to 4-5, depending on the genotype. For the majority of the tested genotypes, strong interactions were observed between data concerning plant behaviour in the field and the presence/number of DNA markers. For nine genotypes, however, correla­tions between phenotypic and molecular study were not found with selected QTLs.
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