Assessment of genetic relationships among Pyrus species and cultivars using AFLP and RAPD markers

Twenty-five Pyrus communis L. cultivars including eight traditional Portugu ese pears, and four commercial Pyrus pyrifolia (Burm.) Nak. (Japanese pear or 'nashi') cultivars were analysed by RAPD and AFLP techniques focusing on their molecular discrimination and the assessment of their genetic related ness. Twenty-five primers generated 324 RAPD markers, among which 271 (84%) were polymorphic. The AFLP technique, using seven primer combinations, rev ealed a similar level of molecular polymorphisms (87%), representing 418 po lymorphic bands among a total of 478 scored in autoradiographs. The high re producibility of RAPD and AFLP techniques was confirmed comparing DNA sampl es from different extractions and different digestions of DNA from the same plant. Three genetic similarity matrices and respective dendrograms were e laborated on using RAPD, AFLP or joint RAPD and AFLP data. Both molecular m arker techniques proved their reliability to assess genetic relationships a mong pear cultivars. P. pyrifolia cultivars exhibit a closer genetic relate dness, clustering apart from P. communis cultivars. Within P. communis, 'Wi lliam's', as well as 'Doyenne du Comice', cluster close to their hybrids. M ost of the Portuguese cultivars tend to cluster together, indicating to con stitute a relatively independent genetic pool, which can be of interest in pear breeding programs.