A Semiselective Agar Medium for IsolatingXanthomonas campestrispv.translucensfrom Wheat Seeds

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Abstract
A semiselective agar medium (XTS agar) was developed and tested for the isolation of X. 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 6 wheat lots and 1 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 [USA], but form 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. The 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. Wheat seeds should be assayed for X. translucens and contaminated seed lots not be grown under sprinkler irrigation.