RESUMO
Symptoms of phytoplasma infection were observed in different weed species, Bidens subalternans, Conyza bonariensis, Heterosperma ovatifolium and Conium maculatum, collected from diverse geographical regions in Argentina. To confirm the association of phytoplasma infection with symptomatic plants, PCR, RFLP and phylogenetic analyses based on 16S rRNA-encoding sequences were performed. In this work, we report the presence of phytoplasmas from group 16SrVII (subgroup 16VII-B) infecting C. bonariensis and B. subalternans and from group 16SrIII (subgroup 16SrIII-X) B. subalternans, H. ovatifolium, and C. maculatum. Phytoplasmas from the aster yellows group were detected infecting C. bonariensis and B. subalternans. Analysis of 16S rRNA-encoding genes revealed the presence of two distinct operons, rrnB (16SrI-B) and newly described rrnA, which is different from the reference RFLP patterns of all previously established 16SrI-subgroups. A single rp operon sequence analysis reveals the presence of simple infection and confirms a description of a novel subgroup. On the basis of these results we propose a designation of new subgroup 16SrI-(B/AJ) AJ (rp-AJ). To our knowledge, this is the first report of phytoplasmas infecting Bidens subalternans¸ Heterosperma ovatifolium and Conium maculatum.
Assuntos
Filogenia , Phytoplasma/classificação , Doenças das Plantas/microbiologia , Plantas Daninhas/microbiologia , Argentina , Técnicas de Tipagem Bacteriana , DNA Bacteriano/genética , Óperon , Phytoplasma/isolamento & purificação , Reação em Cadeia da Polimerase , Polimorfismo de Fragmento de Restrição , RNA Ribossômico 16S/genética , Análise de Sequência de DNARESUMO
China tree yellows (ChTY) phytoplasma is associated with the yellowing disease of the China tree (Melia azedarach) in Argentina. According to partial 16S rRNA gene analysis, ChTY phytoplasma belongs to the 16Sr XIII group, subgroup G. Strains of species of ChTY have 98-99 % 16S rDNA gene sequence similarity with 16SrXIII-group phytoplasmas, and less than 97.5 % when compared to all 'CandidatusPhytoplasma' described so far, except for the novel 'CandidatusPhytoplasma hispanicum'. However, strains of species of ChTY are differentiated from the latter due to having additional molecular and biological attributes. The presence of unique features in the 16S rDNA sequence distinguishes ChTY from all species of 'CandidatusPhytoplasma' currently described. The in silico RFLP profile of 16S rDNA (1.2 kb) and rpLV-rpsC (1.3 kb) genes distinguished ChTY, as in the 16SrXIII-G subgroup within the 16SrXIIII group. The phylogenetic analyses, based on 16S rDNA, rpLV-rpsC and secA gene sequences, in addition to the restricted host range, characteristic symptoms and geographical distribution, confirm that the collective strains of the species ChTY represent a distinct lineage within the phytoplasma clade and support the description of a novel species of 'CandidatusPhytoplasma meliae' with the reference strain being ChTY-Mo3 (Montecarlo, Argentina).
Assuntos
Melia azedarach/microbiologia , Filogenia , Phytoplasma/classificação , Doenças das Plantas/microbiologia , Argentina , Técnicas de Tipagem Bacteriana , Composição de Bases , DNA Bacteriano/genética , Ácidos Graxos , Genes Bacterianos , Phytoplasma/isolamento & purificação , RNA Ribossômico 16S/genética , Análise de Sequência de DNARESUMO
The composition and diversity of the endophytic community associated with yerba mate (Ilex paraguariensis) was investigated using culture-depending methods. Fungi were identified based on their micromorphological characteristics and internal transcribed spacer rDNA sequence analysis; for bacteria 16S rDNA sequence analysis was used. Fungal and bacterial diversity did not show significant differences between organ age. The highest fungal diversity was registered during fall season and the lowest in winter. Bacterial diversity was higher in stems and increased from summer to winter, in contrast with leaves, which decreased. The most frequently isolated fungus was Fusarium, followed by Colletotrichum; they were both present in all the sampling seasons and organ types assayed. Actinobacteria represented 57.5 % of all bacterial isolates. The most dominant bacterial taxa were Curtobacterium and Microbacterium. Other bacteria frequently found were Methylobacterium, Sphingomonas, Herbiconiux and Bacillus. Nitrogen fixation and phosphate solubilization activity, ACC deaminase production and antagonism against plant fungal pathogens were assayed in endophytic bacterial strains. In the case of fungi, strains of Trichoderma, Penicillium and Aspergillus were assayed for antagonism against pathogenic Fusarium sp. All microbial isolates assayed showed at least one growth promoting activity. Strains of Bacillus, Pantoea, Curtobacterium, Methylobacterium, Brevundimonas and Paenibacillus had at least two growth-promoting activities, and Bacillus, Paenibacillus and the three endophytic fungi showed high antagonistic activity against Fusarium sp. In this work we have made a wide study of the culturable endophytic community within yerba mate plants and found that several microbial isolates could be considered as potential inoculants useful for improving yerba mate production.