Submitted to: International Journal of Systematic and Evolutionary Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/5/2011
Publication Date: 1/5/2011
Citation: Lee, I., Bottner-Parker, K.D., Zhao, Y., Villalobos, W., Loreira, L. 2011. "Candidatus phytoplasma costaricanum" a new phytoplasma associated with a newly emerging disease in soybean in Costa Rica. International Journal of Systematic and Evolutionary Microbiology. 61:2822-2826. Interpretive Summary: Phytoplasmas are uncultured bacteria that lack a cell wall and that cause several hundred economically important diseases in plants worldwide. Because of the advance in molecular tools for detection and identification of phytoplasmas, many previously unknown or newly emerged diseases have been diagnosed to be caused by phytoplasmas in the last decades. Thus far more than 1000 phytoplasma strains have been reported and classified into 30 distinct groups and many subgroups. A total of 28 ‘Cadidatus Phytoplasma’ species have been reported. Recently, new diseases with characteristic symptoms induced by phytoplasmal infection occurred in soybean, sweet pepper, and passion fruit in Costa Rica. In collaboration with scientists from Costa Rica, we detected a new phytoplasma in soybean with stunt symptom and closely related strains in both diseased sweet pepper and passion fruit. The soybean stunt (SoyST) phytoplasma is distinct from all the existing phytoplasmas previously reported and represents a new taxon most closely related to 16SrI and 16SrXII stains. We propose that the SoyST phytoplasma represents a novel taxon, ‘Candidatus Phytoplasma costaricanum’. The information will aid implementation of quarantine regulations and it will help extension workers and plant diagnosticians in Costa Rica to determine how to combat the disease.
Technical Abstract: A new phytoplasma associated with a newly emerging disease, soybean stunt (SoyST), in soybean (Glycine max) was found in 2002 in a soybean plantation in Alajuela Province, Costa Rica. The same or very closely related phytoplasma also infected sweet pepper (Capsicum annuum) with purple vein syndrome (SwPPV) and passion fruit (Passiflora edulis) vines with bud proliferation (PasFBP) in the same region. Sequence analysis of cloned 16S rDNAs (GenBank Accession Nos. FJ226068–FJ226073 and HQ225624-HQ225635) indicated that the affected plants were infected by phytoplasmas that shared less than 97.5% sequence similarity with any of the previously classified phytoplasmas, and, as such, represent a new taxon, most closely related to phytoplasma group16SrI and 16SrXII strains. Virtual RFLP analysis indicated that the new phytoplasma and the closely related strains represent a new 16Sr group, designated16SrXXXI. Phylogenetic analysis of 16S rRNA gene sequences from the new phytoplasma strains, previously described ‘Candidatus Phytoplasma spp’, and other distinct unnamed phytoplasmas indicated that soybean stunt (SoyST) phytoplasma represents a distinct lineage within the aster yellows/stolbur branch on the phylogenetic tree. On the basis of unique 16S rRNA gene sequences and biological properties, we propose that the new SoyST phytoplasma represents a novel taxon, ‘Candidatus Phytoplasma costaricanum’, with SoyST1c1R as the reference strain.