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 m ycoplasmalike organisms (MLOs) associated with two grapevine yellows d iseases (strain FDU of flavescence doree MLO from northern Italy and s train FDB of southern European grapevine yellows MLO from southern Ita ly) and Italian periwinkle virescence disease (MLO strain G from north ern Italy). Results from dot hybridizations using six probes containin g 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 pattern s of chromosomal DNA from southern European grapevine yellows MLO stra in FDB exhibited some similarities with those from MLO strain G but we re markedly different from those exhibited by DNA from flavescence dor ee MLO strain FDU. The results indicate that at least two distinct MLO s are associated with grapevine yellows in Italy.