Identification of phytoplasmas associated with a decline of European hackberry (Celtis australis)

The presence of phytoplasmas in declining trees of European hackberry was demonstrated for the first time using polymerase chain reaction assays with primers amplifying phytoplasma 16S rDNA regions. Restriction fragment length polymorphism analysis of these DNA fragments together with PCR, employing primers specific for particular phylogenetic groups of phytoplasmas, made it possible to detect the presence of aster yellows group (16SrI) related phytoplasmas. These were classified into two different subgroups (I-B and I-C) and were present in both symptomatic and asymptomatic hackberry plants. Aster yellows-related phytoplasmas were found in all the root samples collected during the winter. In addition, phytoplasmas from the peach X disease group (16SrIII) were found in four out of 10 root samples; in five root samples phytoplasmas of the elm yellows group (16SrV) were also present.