VIEW ARTICLE

Techniques

A Semiselective Agar Medium for Isolating Xanthomonas campestris pv. translucens from Wheat Seeds. N. W. Schaad, Department of Plant, Soil and Entomological Sciences, University of Idaho, Moscow 83843; R. L. Forster, research and Extension Center, Kimberly, ID 83341. Phytopathology 75:260-263. Accepted for publication 4 October 1984. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/Phyto-75-260.

A semiselective agar medium (XTS agar) was developed and tested for the isolation of Xanthomonas campestris pv. translucens (hereafter referred to as X. translucens) from seeds of wheat (Triticum aestivum). XTS agar contained Difco nutrient agar, glucose, cycloheximide, gentamycin, and cephalexin. More than 91% of the seed-associated saprophytic bacteria washed from seeds of six wheat lots and one barley (Hordeum vulgare) lot were inhibited on XTS agar. X. translucens was isolated on XTS agar from 15 of 19 randomly obtained commercial wheat seed lots in Idaho but from only three of the 19 lots assayed on nutrient glucose agar. Comparison of results of assaying washings from samples of seed lots with different levels of natural contamination by X. translucens onto XTS agar and sowing samples of the same seed lot in the field showed the former to be more sensitive. Our frequent isolation of X. translucens from wheat seed lots suggests that seed contamination may be a factor in recent epiphytotics of black chaff in sprinkler-irrigated wheat fields in southern Idaho. We suggest that wheat seeds be assayed for X. translucens and that contaminated seed lots not be grown under sprinkler irrigation.