Specific PCR to detect European stone fruit yellows phytoplasma
A specific PCR assay has been developed in France to detect the European stone fruit yellows phytoplasma (ESFY - quarantine status under review). PCR primers were designed according to the partial sequence of a non-ribosomal genomic fragment of European stone fruit yellows phytoplasmas obtained by direct sequencing of a specific PCR product. With these primers, a specific, sensitive and reliable detection of ESFY can be achieved. No PCR products were obtained from healthy control or plants affected by various other phytoplasmas (apple proliferation and pear decline phytoplasmas). This new detection tool was tested on many samples representing all Prunus species grown in France (apricot, Japanese plum, European plum, peach, sweet cherry, almond) and collected from all Prunus-producing regions. Most samples were collected on trees showing symptoms of phytoplasma diseases. ESFY was detected in samples from 114 out of the 139 examined orchards. The presence of typical symptoms (e.g. off-season growth in winter and chlorotic leaf roll in summer) was highly correlated with the presence of ESFY (in 95% studied cases). In addition, ESFY was detected in 51% of samples derived from trees showing non-specific symptoms, this could mean that ESFY is more widespread in the orchards than previously thought. The authors have also found that for a large number of samples, ESFY could be detected in the aerial parts of the trees in winter which is particularly useful in routine detection procedures for quarantine and certification purposes (as multiplication material is sold as dormant budwood). It is also noted that ESFY has been detected for the first time in France in almond, but not in cherry although 12 trees had been sampled in the Molières region where 20 years ago a severe decline had been reported (Molières disease which is thought to be caused by ESFY).
Sources
Jarausch, W.; Lansac, M.; Saillard, C.; Broquaire, J.M.; Dosba, F. (1998) PCR assay for specific detection of European stone fruit yellows phytoplasmas and its use for epidemiological studies in France.
European Journal of Plant Pathology, 104(1), 17-27.