Detection and molecular characterisation of an alfalfa phytoplasma in Argentina that represents a new subgroup in the 16S rDNA Ash Yellows group(‘Candidatus Phytoplasma fraxini’)

Abstract

A phytoplasma infecting alfalfa crops was detected and characterised in Argentina, the Argentinean Alfalfa witches¢-broom (ArAWB) phytoplasma. Typical witches¢-broom symptoms were observed in diseased alfalfa plants from fields of the 'Cuyo' region in the Andean midwest. Pleomorphic bodies were observed by electron microscopy in sieve tubes of the diseased plants. The results obtained from the sequence homology, similarity coefficients derived from RFLP of the 16S rDNA and phylogenetic analysis led us to include this phytoplasma in the 16Sr VII (Ash Yellows) group. However, the ArAWB phytoplasma showed several differences when compared to other members of group 16Sr VII. The RFLP analysis of partial 16S rRNA gene of two ArAWB isolates, digested with 16 restriction enzymes, showed differences between the ArAWB and the reference strain (AshY1 T ) in six enzyme patterns. Restriction patterns unique for the group and an exclusive HinfI restriction site were found in the ArAWB phytoplasma rDNA. Moreover, the similarity coefficients (0.92-0.86) were lower than those obtained among other group members. The significant differences detected suggested that this phytoplasma belonged to a subgroup different from those described so far. We propose therefore, that the ArAWB phytoplasma should be included in a new VII-C subgroup, closely related to the EriWB phytoplasma (VII-B) described in Brazil.

Phytoplasmas and Phytoplasma Diseases: A Severe Threat to Agriculture

“…VII-B Erigeron witches' broom (ErWB) AY034608 [180] VII-C Argentinian alfalfa witches' broom (ArAWB) AY147038 [181] 16SrVIII: Loofah witches' broom (Asia)…”

The underestimated diversity of phytoplasmas in Latin America

“…Phytoplasma fraxinis'), 16SrVII-B (Erigeron witches'-broom phytoplasma), 16SrVII-C (Argentinian alfalfa witches'-broom phytoplasma) and the recently identified 16SrVII-D (EboWB-Br01), group 16SrVII is one of the least diverse groups in terms of distribution and plant hosts affected (Griffiths et al, 1999;Conci et al, 2005;Meneguzzi et al, 2008;Flôres et al, 2015). The new subgroup detected in this study, subgroup 16SrVII-E, is represented by Chilean grapevine yellows phytoplasma (GenBank accession no.…”

Detection of Bacterial and Phytoplasmal Pathogens

“…When digested with 16 restriction enzymes the profiles revealed distinct differences between the ArAWB isolates and when disgested with six enzymes, the profiles revealed distinct differences between the ArAWB and the reference strain (AshY1 T ). Restriction patterns unique for the group and an exclusive Hinf 1 restriction site were found in the ArAWB phytoplasma DNA (Conci et al 2005). Tomato big bud (TBB) phytoplasma belonging to group 16SrII occurring in Brazil was detected by RFLP analysis using endonucleases HhaI and RsaI (Mello et al 2006).…”