SEED TREATMENTS FOR ERADICATING CLAVIBACTER-MICHIGANENSIS SUBSP MICHIGANENSIS FROM NATURALLY INFECTED TOMATO SEEDS

Clavibacter michiganensis subsp. michiganensis, the causal agent of bacterial canker, was eradicated from naturally infected tomato (Lycopersicon esculentum) seeds that were soaked in 0.6 M HCl for 5 hr, in 0.25 or 0.50% acidified cupric acetate (ACA) for 20 min, or in water at 52 C for 20 min or at 56 C for 30 min. Other individual treatments failed to eradicate the pathogen. Most treatments reduced the saprophytic bacterial flora on tomato seeds; however, only the HCl treatment and treatment with ACA (0.25%) at 52 C for 20 min eradicated saprophytes. Germination of treated seed varied with the germination test. In the blotter test, all individual treatments that eradicated C. m. subsp. michiganesis, except water at 56 C significantly (P = 0.05) reduced germination. In contrast, only the HCl treatment significantly reduced the germination of seed planted in steam-sterilized soil (UC soil mix), and seed treated with hot water (52 C for 20 min) germinated at a greater rate than the untreated controls.