POLYMORPHISM OF INSERTION SITES OF TY1-COPIA CLASS RETROTRANSPOSONS AND ITS USE FOR LINKAGE AND DIVERSITY ANALYSIS IN PEA

A sample of 15 cultivars and 56 Pisum accessions from the JIC germplas m core collection has been studied using a modification of the SSAP (s equence-specific amplification polymorphisms) technique; the specific primer was designed to correspond to the polypurine tract (PPT) of PDR 1, a Ty1-copia group retrotransposon of pea. Most of these SSAP produc ts were shown to be PDR1 derived. The PDR1 SSAP markers are more infor mative than previously studied AFLP or RFLP markers and are distribute d throughout the genome. Their pattern of variation makes them ideal f or integrating genetic maps derived from related crosses. Data sets ob tained with AFLP and PDR1 SSAP markers were used to construct neighbou r-joining trees and for principal component analysis. These data sets give greater resolution than hitherto available for the characterisati on of variation within Pisum, showing that the genus has three main gr oups: P. fulvum, P. abyssinicum and all other Pisum spp. P. abyssinicu m is not a subgroup of cultivated P. sativum, as was previously though t, but has probably been domesticated independently. Modern cultivars are shown to form a single group within Pisum as a whole.