RESTRICTION-FRAGMENT-LENGTH-POLYMORPHISM ANALYSES AND DOT HYBRIDIZATIONS DISTINGUISH MYCOPLASMALIKE ORGANISMS ASSOCIATED WITH FLAVESCENCE-DOREE AND SOUTHERN EUROPEAN GRAPEVINE YELLOWS DISEASE IN ITALY

Biotinylated cloned DNA probes were employed in dot hybridizations and restriction fragment length polymorphism (RFLP) analyses to compare mycoplasmalike organisms (MLOs) associated with two grapevine yellows diseases (strain FDU of flavescence doree MLO from northern Italy and strain FDB of southern European grapevine yellows MLO from southern Italy) and Italian periwinkle virescence disease (MLO strain G from northern Italy). Results from dot hybridizations using six probes containing cloned DNA of MLO strain FDU, of MLO strain G, or of American aster yellows MLO strain AY1, revealed that FDU and FDB shared some regions of DNA sequence homology with one another as well as with MLO strains G and AY1, but all four MLOs were mutually distinguished. RFLP patterns of chromosomal DNA from southern European grapevine yellows MLO strain FDB exhibited some similarities with those from MLO strain G but were markedly different from those exhibited by DNA from flavescence doree MLO strain FDU. The results indicate that at least two distinct MLOs are associated with grapevine yellows in Italy.