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In the summer of 1999, typical yellows-type symptoms were observed on garlic and green onion plants in a number of gardens and plots around Edmonton, Alberta, Canada. DNA was extracted from leaf tissues of evidently healthy and infected plants. DNA amplifications were conducted on these samples, using two primer pairs, R16F2n/R2 and R16(1)F1/R1, derived from phytoplasma rDNA sequences. DNA samples of aster yellows (AY), lime witches'-broom (LWB) and potato witches'-broom (PWB) phytoplasmas served as controls and were used to determine group relatedness. In a direct polymerase chain reaction (PCR) assay, DNA amplification with universal primer pair R16F2n/R2 gave the expected amplified products of 1.2 kb. Dilution (1/40) of each of the latter products were used as template and nested with specific primer pair R16(1)F1/R1. An expected PCR product of 1.1 kb was obtained from each phytoplasma-infected garlic and green onion samples, LWB and AY phytoplasmas but not from PWB phytoplasma. An aliquot from each amplification product (1.2 kb) with universal primers was subjected to PCR-based restriction fragment length polymorphism (RFLP) to identify phytoplasma isolates, using four restriction endonucleases (AluI, KpnI, MseI and RsaI). DNA amplification with specific primer pair R16(1)F1/R1 and RFLP analysis indicated the presence of AY phytoplasma in the infected garlic and green onion samples. These results suggest that AY phytoplasma in garlic and green onion samples belong to the subgroup 16Sr1-A.

Typical phytoplasma yellows symptoms were observed in parsnip (Pastinaca sativa L.) plants grown around Edmonton, Alberta, Canada. Examination of ultrathin sections of leaf midribs by electron microscopy revealed numerous phytoplasma bodies localized in the phloem cells. DNA extracted from the infected 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 member of the aster yellows (AY) group by amplification with the specific primer pair R16(1)/F1/R1 that was designed on the basis of AY phytoplasma 16S rDNA sequences. In the nested PCR assays, the expected DNA fragment of 1.1 kb was amplified with this specific primer set. Similar restriction patterns were found for the 1.1 kb PCR products of the phytoplasma isolated from parsnip and an AY phytoplasma control after digestion with restriction endonucleases AluI, HhaI, KpnI and RsaI. This is the first reported observation of aster yellows in parsnip in Canada.