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Occurrence of Corn Stunt Spiroplasma at Different Elevations in Mexico. Narceo B. Bajet, Associate Scientist, International Maize and Wheat Improvement Center (CIMMYT), Apartado Postal 6-641, 06600 Mexico, D.F., Mexico. B. L. Renfro, Pathologist, International Maize and Wheat Improvement Center (CIMMYT), Apartado Postal 6-641, 06600 Mexico, D.F., Mexico. Plant Dis. 73:926-930. Accepted for publication 24 April 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0926.

A survey of Spiroplasma kunkelii, or corn stunt spiroplasma (CSS), was conducted in Mexico from October 1985 to March 1988 using phase contrast or dark field light microscopy (DFM) and enzyme-linked immunosorbent assay (ELISA). Three types of symptoms were observed: consistently stunted plants whose leaves had well-defined broad chlorotic streaking and that were usually observed at 60940 m above sea level, plants that were not always stunted but whose leaf margins showed red to purple streaks, and plants that usually were not stunted but whose leaves showed either a diffuse yellow or a chlorotic stripe condition with or without red margins. Both the second and third symptom types were observed at all elevations surveyed and usually appeared around 7 days before or after anthesis. ELISA was better than DFM at detecting CSS, but both methods demonstrated that all samples with the first type of symptom, 5170% of those with the second type, 4346% of those with the third type, and 311% of those without symptoms were infected with CSS. The disease was more prevalent at lower than at higher elevations. These results indicate high prevalence and wide distribution of CSS in Mexico and also confirm that maize plants having reddish or purplish leaves are often infected with CSS.

Keyword(s): incidence, mollicute, resistance.