Acerola shoot proliferation induced by a phytoplasma enclosed in the subgroup 16SrIII-F

Acerola bushes were observed showing symptoms of shoot proliferation, generalized stunting, yellowing and decline. Since these symptoms are typically induced by phytoplasmas, this survey was carried out with the aim of detecting, identifying and classifying the supposed phytoplasma present in symptomatic bushes. Total DNA was extracted from symptomatic and asymptomatic samples and used in nested PCR conducted by the primer pairs R16mF2/mR1 followed by R16F2n/R2. Amplifications of expected genomic fragments of 1.2 kb revealed the presence of phytoplasma in 73 % of the symptomatic samples. Molecular analyses, using computer-simulated RFLP patterns, similarity coefficient calculation and phylogenetic analysis allowed for classifying the bacterium as a 'Candidatus Phytoplasma pruni' - related strain (subgroup 16SrIII-F). The phytoplasma induced the same symptoms in healthy acerola plants inoculated by grafting and showed molecular identity with the strain identified in naturally infected bushes. Although various strains belonging to distinct subgroups within the 16SrIII group have been previously identified in Brazil, this is the first report of the presence of a representative of the 16SrIII-F subgroup in the Brazilian agroecosystem. Considering that phytoplasmas can be systemically distributed throughout the plant and acerola plants are vegetatively propagated, it is recommended that propagation material be obtained from mother plants free of the pathogen.

Molecular characterization of a phytoplasma associated with a commercial variety of Momordica charantia

Momordica charantia (bitter melon) presents two distinct types or varieties, known as wild type and commercial type. Plants of the wild type are hosts of a phytoplasma of the group 16SrIII-J, which is associated with a disease known as witches’ broom. However, this disease has not yet been reported in commercial bitter melon. Thus, symptomatic plants of the commercial type were analyzed in order to demonstrate the association between phytoplasmas and disease. In further assays, strains found in symptomatic plants of the commercial type were subjected to analysis of sequences of the secY gene to determine the extent of genetic diversity. Amplification of DNA fragments from genes 16Sr rRNA (1.2Kb) and secY (1.6Kb) revealed association of phytoplasma with symptomatic plants of the commercial type. Virtual Restriction Fragment Length Polymorphism (RFLP) analysis identified this phytoplasma as a member of the subgroup 16SrIII-J. Phylogenetic analysis showed that the phytoplasma was closely related to the representative of the 16SrIII-J subgroup. Molecular analysis indicated that the secY gene, in spite of the greater genetic variation compared with 16S rRNA gene, did not separate strains of the phytoplasma of the subgroup 16SrIII-J among those strains present in M. charantia.

Molecular characterization of a phytoplasma associated with a commercial variety of Momordica charantia

Momordica charantia (bitter melon) presents two distinct types or varieties, known as wild type and commercial type. Plants of the wild type are hosts of a phytoplasma of the group 16SrIII-J, which is associated with a disease known as witches broom. However, this disease has not yet been reported in commercial bitter melon. Thus, symptomatic plants of the commercial type were analyzed in order to demonstrate the association between phytoplasmas and disease. In further assays, strains found in symptomatic plants of the commercial type were subjected to analysis of sequences of the secY gene to determine the extent of genetic diversity. Amplification of DNA fragments from genes 16Sr rRNA (1.2Kb) and secY (1.6Kb) revealed association of phytoplasma with symptomatic plants of the commercial type. Virtual Restriction Fragment Length Polymorphism (RFLP) analysis identified this phytoplasma as a member of the subgroup 16SrIII-J. Phylogenetic analysis showed that the phytoplasma was closely related to the representative of the 16SrIII-J subgroup. Molecular analysis indicated that the secY gene, in spite of the greater genetic variation compared with 16S rRNA gene, did not separate strains of the phytoplasma of the subgroup 16SrIII-J among those strains present in M. charantia.(AU)