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• Genetic relatedness among Asian Cotoneaster species investigated with DNA marker analysis

  43-46.

  H. Nybom

  I. V. Bartish

  J. Fryer

  Views:

  153

  The widespread genus Cotoneaster has its centre of diversity in the Himalayas and surrounding areas. Most taxa appear to be polyploid and apomictic, and many of them have become popular ornamentals due to their attractive foliage and berries. One of the taxonomically most critical groups is Section Alpigeni which contains several important ornamental plants. The number of species belonging to this section varies widely between different taxonomic treatises, depending on whether 'splitting' or 'lumping' of species is preferred. Using a rather narrow species definition, we have investigated 13 different species using RAPD analysis. A simple matching (SM) coefficient-based principle coordinate analysis (PCO) was calculated from the RAPD data. Some species were clearly more similar to each other than to other species in the analysis. The levels of similarity did, however, not correspond very well to the lumping together of several taxa under the same species name as performed e.g. in the recent Flora of China. Obviously, the complex hybridogenous origination and, in some cases, still ongoing recombination with sexual species or among the apomictic taxa themselves, produces a genetic variability structure that cannot be properly reflected in a hierarchical taxonomy.

• Application of DNA markers for detection of scab resistant apple cultivars and selections

  59-63.

  H. Mattisson

  H. Nybom

  Views:

  105

  A DNA marker-based study was undertaken to identify the occurrence of major scab resistance genes in some apple cultivars and selections of importance for apple breeding. Unfortunately none of the RAPD-based markers previously reported to detect the V_a, V_b, V_r and V_x genes produced unambiguous results. By contrast, the CAPS marker MI8 produced the expected three bands in all cultivars and selections already known or suspected to have the V_f gene, as well as in the Russian cultivar 'Antonovka Polotora Funtovaja' suspected to have V_a resistance which however may be allelic to V_f. V_f-carrying selections and newly named cultivars 'Frida' and 'Fredrik' are grown successfully in Sweden without fungicides, suggesting that the V_r resistance breaking scab races 6 and 7 have not yet become a problem. The SCAR marker B12 detected the V_m gene in 'Prairifire', 'Rouville', clones 'OR45T132' and 'OR48T70', and selection '16-36-193'. The SSR locus 0102b10 detected one band at 118 by in 'Reka'. This is presumed to be identical to the V_r gene marker previously reported.