Eradication ofXanthomonas campestris,the Causal Agent of Black Rot, fromBrassicaSeeds with Antibiotics and Sodium Hypochlorite

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Abstract
A method is needed for eradicating X. campestris from Brassica seeds without causing damage to seeds or phytotoxicity to seedlings. The pathogen was eradicated from most lots of Brassica seeds by a 1 h soak in a 500 .mu.g/ml solution of either aureomycin, terramycin or streptomycin. These treatments were phytotoxic, but if the antibiotic soak was followed with a water rinse and a soak for 30 min in 0.5% (wt/vol) NaOCl, the phytotoxicity was eliminated. Laboratory, greenhouse and field tests indicated that a soak for 2 h in a solution containing any one of these antibiotics followed by the water rinse and a NaOCl soak eradicated X. campestris from all seed lots tested and was not phytotoxic. When preceded with a reduced-pressure 0.2% (wt/vol) thiram soak for 24 h, both Phoma lingam and X. campestris were eradicated from cabbage seeds with no loss of seed quality. By comparison, the standard hot water soak did not eradicate X. campestris from 3 of 11 lots tested, and it frequently damaged seed quality. A soak in 500 .mu.g/ml of vancomycin HCl was not phytotoxic, but in field tests seeds treated with this antibiotic produced infected plants. Efforts are under way to register a seed soak in 500 .mu.g/ml streptomycin for 2 h followed by a water rinse and a 30 min soak in 0.5% NaOCl for eradication of seed-borne X. campestris in the USA.