Semiselective agar medium for isolation of Clavibacter michiganense subsp. michiganense from tomato seed.
The new medium, designated SCM (semiselective medium for C. michiganense), contained sucrose, mono- and dipotassium phosphate, magnesium sulphate, yeast extract, nicotinic acid, boric acid, nalidixic acid, potassium tellurite and cycloheximide. Recovery of 34 strs of C. michiganense on SCM in comparison with nutrient broth yeast extract (NBY) medium ranged from 85 to 132%, and >98% of the recoverable tomato seed saprophytic bacteria growing on NBY did not grow on SCM. SCM was quantitatively and qualitatively superior to other selective media for C. michiganense. Extracting seed by blending for 10-15 min in a commercial lab. blender resulted in an increase of 100% or more over washing seeds in a flask at 4°C for 72 h. A single contaminated seed containing as few as 50 c.f.u. of C. michiganense was detectable in samples of 10 000 seeds.