FIRST REPORT OF A “CANDIDATUS PHYTOPLASMA SOLANI” RELATED STRAIN ASSOCIATED WITH A DISEASE OF DATURA STRAMONIUM IN GREECE

Abstract

Jimsonweed (Datura stramonium), family Solanaceae, a common weed in spring crops in Greece, includes two botanical varieties (var. stramonium and var. tatula). During a field trial at the Aristotle University Farm (40o32N’ 22o59’E, 6 m asl), in which four accessions of D. stramonium were tested for growth rate and alkaloid content, phytoplasma-like symptoms were observed. Initially, the affected plants showed interveinal chlorosis of the upper leaves, stunting and flower malformation, whereas at maturity they did not form normal fruits and developed leaf necrosis. To investigate the possibility of a phytoplasma infection, DNA was extracted from leaf samples of symptomatic and apparently healthy plants of both varieties according to Psifidi et al. (2010). A nested PCR was performed using two universal primer sets specific to the phytoplasma 16S rRNA gene: P1/P7 (Schneider et al., 1995) followed by R16F2n/R16R2 (Gundersen and Lee, 1996). The expected ca. 1,200 bp product, amplified esclusively from symptomatic plants of both varieties, was cloned and sequenced. BLAST analysis revealed 99% similarity with sequence AF248959 of stolbur phytoplasma (16SrXII group, Ca. Phytoplasma solani). Sequences from both varieties were identical, indicating infection by the same phytoplasma strain and were deposited in EMBL-EBI (accession Nos HE598778 and HE598779). Diseased plants of var. tatula and stramonium showed 49-69% and 38% reduction of the above-ground fresh weight, respectively, compared to healthy plants, hence making the phytoplasma an important pathogen of jimsonweed, which constitutes a reservoir plant in the field. This is, to our knowledge, the first report of a Ca. Phytoplasma solani-related disease in jimsonweed in Greece.