Abstract
Immunofluorescent staining, dot blot hybridization, PCR, random amplified polymorphic DNA (RAPD) markers, and restriction fragment length polymorphism wee used to study the genetic relatedness among mycoplasmalike organisms (MLOs) associated with several geographically diverse grapevine yellows diseases (CA1, CH1, SA1, and SA2 from Bologna, Italy; GYU from Udine, Italy; GYR from Rome, Italy; and GYG from Germany). The relationship between these and MLOs associated with clover phyllody diseases in Italy (CPhB and CPhC) and Canada (CPhCa) was also examined. Two monoclonal antibodies reacted with MLOs of GYU-, CPhB-, and CPhC-infected periwinkles. Dot blot hybridization with two cloned GYU DNA fragments, GYD-1 and GYD-2 inserts, showed that both hybridized with DNAs of GYU-, CPhB-, and CPhC-infected periwinkles but not with those of GYR and CPhCa. In addition, GYD-1 insert hybridized with DNAs of CA1, CH1, SA1, SA2, and GYG. Three primer pairs were developed in PCR experiments for this study. By using primer set GYD2P1F and GYD2P1R, a 600-bp DNA fragment was amplified only when DNAs from GYU-, CPhB-, and CPhC-infected plants were used as templates. With the primer pair GYD2P1F and GYD2P2R, a 550-bp DNA fragment was amplified from GYU, CPhB, CPhC, and GYG. The primer pair GYD1P1F and GYD1P2R, on the other hand, could amplify all isolates, although the patterns of PCR products were not identical for all isolates.(ABSTRACT TRUNCATED AT 250 WORDS)