The slime polysaccharide of X. campestris pv. oryzae caused wilting in rice cuttings. This substance was high molecular and was precipitated by ethanol. Wilt inducing potential of slime polysaccharides of virulent and avirulent clones could not be differentiated. The slime polysaccharide of all clones was composed of arabitol, mannose, glucuronolactone, glucose and glucuronic acid. The ratios of these sugars were quite different between large colony type and small colony type. In general, arabitol and glucose contents of slime polysaccharides were higher in small colony types (St and Sm) than in large colony types (Lw, Ld and Lh). Column chromatography on Sephadex G-200 revealed that the slime polysaccharides of each clone were heterogeneous in molecular weight. The wild type was composed of relatively greater amount of high molecular weight polysaccharide whereas the small colony type variants were of relatively low molecular ones. Intermediate types such as Ld and Lh were composed of both these types.
The hapten inhibition studies were carried out by using sugars of slime polysaccharide component and anti-Q7472-serum. In the case of the isolate Q7472 (serovar A), glucose, mannose and glucuronic acid inhibited precipitin reaction, while in the cases of Q7502 (serovar B-I) and N5837 (serovar B-II), glucuronic acid and glucuronolactone were strong promotors of the precipitin reaction. These facts suggest that the component sugars of a major portion of the immunogenic regions are remarkably different with serovars.