Submitted to: American Phytopathological Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 5/22/1998
Publication Date: N/A
Technical Abstract: For many years, soybeans in Wisconsin have exhibited symptoms that could not be explained purely by traditional pathogens (fungi, bacteria, viruses, nematodes), nutrient imbalances, herbicide injury, poor soil conditions, or the "the weather". Such symptoms include: "bushy" or "stunted" plants, purple streaks and patches on stems, yellow blotches or marginal necrosis on leaves, stems that remain green even after leaves and pods have matured bud proliferation, reduction in the number of pods per node, dull seed coats, relatively dark, bluish foliage. The symptoms described above are more severe in affected plants at cooler temperatures. Initial diagnosis by 4',6-diamidino-2-phenyl-indole*2HC1 (DAPI) and Dienes' stains suggested that phytoplasmas (plant pathogenic Mollicutes) or other prokaryotes may be associated with this soybean disorder. Nested PCR using phytoplasma-specific primers detected phytoplasmas from symptomatic soybean nsamples. Two distinct phytoplasma belonging to the clover proliferation group (R16SrVI) and the aster yellows group, subgroup B (16SrI-B) were identified by RFLP analysis of PCR amplified 16SrDNA sequence. The phytoplasma belonging to the R16SrVI group predominates in all symptomatic soybeans. Some symptomatic soybean are doubly infected with both phytoplasmas. Studies have been undertaken to determine the distribution and impact of phytoplasmas on soybean health and yield.