Tolerance Levels of Seedborne Xanthomonas Campestris Pv. Translucens, the Causal Agent of Black Chaff of Wheat

Black chaff, caused by Xanthomonas campestris pv. translucens(hereafter referred to as X. translucens), has caused large yield reductions in irrigated wheat in southern Idaho recently. A seed assay using a semiselective agar medium (XTS agar) for detection of the pathogen was recently described (Phytopathology 75:260–263). Field studies were conducted in 1983 and 1984 to quantify the relationship between the level of X. translucens contamination (naturally infected and/or infested) in the seed with black chaff development in the field. In both years, different levels of contamination in wheat seed lots were achieved by mixing contaminated seed with 0, 90, and 99% foundation seed. The foundation seed had a trace level of X. translucens.