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Plants of Rudbeckia hirta L. exhibiting symptoms characteristic of viral (plant stunting, flower distortion, necrotic spots on leaves) and phytoplasmal (general yellows, stunting, virescence) diseases were collected for investigation. The causal agent of viral disease, Cucumber mosaic virus (CMV), was isolated and identified by the methods of test-plants, electron microscopy, DAS-ELISA, and reverse transcription polymerase chain reaction (RT-PCR). The causal agent of phytoplasmal disease was detected in polymerase chain reactions (PCRs) using phytoplasma universal primer pairs P1/P7 and R16F2n/R16R2 and DNA extracted from diseased rudbeckias. The 1.2 kbp 16S rDNA product was subjected to single enzyme digestions with 9 different restriction endonucleases. Restriction fragment length polymorphism (RFLP) analysis revealed that rudbeckia plants were infected by phytoplasma belonging to group 16SrI (aster yellows phytoplasma group), subgroup M. [ABSTRACT FROM AUTHOR]

Plants of sneezeweed (Helenium L.) exhibiting symptoms characteristic of diseases: viral (plant stunting, flower breaking) and phytoplasmal (general yellows, flower virescence, phyllody) were collected for investigation. The causal agent of viral disease, Tomato ringspot nepovirus, was isolated and identified by the methods of test-plants and electron microscopy. The causal agent of phytoplasmal disease was detected in polymerase chain reactions (PCRs) using phytoplasma universal primer pairs P1/P7 and R16F2n/R16R2. The 1.2 kbp 16S rDNA product was subjected to single enzyme digestions with 10 different restriction endonucleases. Restriction fragment length polymorphism (RFLP) analysis revealed that sneezeweed plants were infected by phytoplasma belonging to group 16SrI (aster yellows phytoplasma group), subgroup I-A, which type strain is tomato big bud phytoplasma. [ABSTRACT FROM AUTHOR]