GENETIC COMPARISON OF THE PEACH YELLOW LEAF ROLL AGENT WITH EUROPEAN FRUIT TREE PHYTOPLASMAS OF THE APPLE PROLIFERATION GROUP

Restriction fragment length polymorphism (RFLP) analysis of PCR-amplif ied ribosomal DNA and Southern blot hybridization using cloned chromos omal DNA fragments from the apple proliferation (AP) phytoplasma as pr obes were used to investigate the genetic relationship of the Californ ia peach yellow leaf roll (PYLR) agent with phytoplasmas causing fruit tree diseases in Europe. This comparison showed that the California P YLR phytoplasma is closely related to apple proliferation (AP), pear d ecline, and European stone fruit yellows phytoplasmas and that it is a member of the phylogenetic AP group. The PYLR agent could clearly be distinguished from the AP and European stone fruit yellows phytoplasma s by Southern blot hybridization with DNA fragments from the AP phytop lasma and by RFLP analysis of ribosomal DNA employing SspI, BsaAI, and RsaI restriction endonucleases. However, the PYLR phytoplasma was ind istinguishable from the pear decline agent by RFLP analysis of PCR-amp lified ribosomal DNA.