The identification of a phytoplasma from the Aster Yellows group infecting sugar beet in Hungary

Abstract

In September 1999, sugar beet from several fields in Hajdszovat, Hungary (in the Kaba sugar factory region) were identified showing unusual symptoms, including a ‘pineapple-shaped’ crown, and stunted, chlorotic and necrotic leaves and petioles, with recent re-growth being small and deformed. In some cases, up to 60% of the crop was showing symptoms. The observed symptoms were similar to those described for ‘low sugar disease’, a condition previously recorded only in France, which is putatively associated with a phytoplasma of the Stolbur group and is believed to be vectored by the leaf hopper, Pentastiridius beieri (Munchembled et al., 1999). As a result of these similarities, and as extensive testing had failed to identify any other pathogens as the potential cause, samples were tested for phytoplasma infection. DNA was extracted from symptomatic plants (three in total) using an enrichment procedure (Ahrens & Seemuller, 1992) and tested using PCR with universal nested 16S rRNA primers (Gundersen & Lee, 1996). In all cases, a single product (1246 bp) was obtained (none was obtained from healthy beet controls). One of these products was cloned and sequenced. Subsequent BLAST analysis showed that the obtained sequence (accession no. AF245439) shared closest homology with 16S rRNA sequences from members of the Aster Yellows (16SrI) group. The greatest similarity was with a phytoplasma isolated from winter oilseed rape in the Czech Republic (accession no. U89378) and onion yellows from Japan (accession no. D12569), with 99·7% and 99·3% sequence identity, respectively. Both phytoplasmas are classified within subgroup 16SrI-B (Bertaccini et al., 1998). The rape phytoplasma is thought to be the same as those previously described as rape green petal or phyllody, found in Germany and Hungary (Bertaccini et al., 1998). This is the first definitive record of a phytoplasma infecting sugar beet in Hungary.