Molecular and microscopical detection of aster yellows phytoplasma associated with infected parsnip

Typical phytoplasma yellows symptoms were observed in parsnip (Pastinaca sa tiva L.) plants grown around Edmonton, Alberta, Canada. Examination of ultr athin sections of leaf midribs by electron microscopy revealed numerous phy toplasma bodies localized in the phloem cells. DNA extracted from the infec ted leaves was amplified with a 16S rDNA universal primer pair P1/P6 giving the expected PCR product of 1.5 kb. The phytoplasma was confirmed as a mem ber of the aster yellows (AY) group by amplification with the specific prim er pair R16(1)/F1/R1 that was designed on the basis of AY phytoplasma 16S r DNA sequences. In the nested PCR assays, the expected DNA fragment of 1.1 k b was amplified with this specific primer set. Similar restriction patterns were found for the 1.1 kb PCR products of the phytoplasma isolated from pa rsnip and an AY phytoplasma control after digestion with restriction endonu cleases AluI, HhaI, KpnI and RsaI. This is the first reported observation o f aster yellows in parsnip in Canada.