Serovars of Xanthomonas campestris pv. oryzae Collected from Asian Countries

Abstract

By means of gel diffusion test with antisera produced against Xanthomonas campestris pv. oryzae isolates Q7472 (pathogenic group I) and Q7502 (pathogenic group IV), three serovars, A, B-I and B-II, were designated in X. campestris pv. oryzae isolates collected from Asian countries. Among 160 isolates tested, 132 produced precipitin bands with both antisera and were designated as serovar A. The other 28 isolates gave bands with anti-Q7502-serum but not with anti-Q7472-serum and were designated as serovar B. Serovar B was further separated into B-I and B-II, in terms of heat tolerance of antigen. Among 28 isolates belonging to serovar B, 20 fell into B-I because they did not show any changes in reaction pattern even if heat treatment (dip into boiling water for 1hr) was given to the antigens. The remaining 8 isolates were designated as B-II as they lost their antigenicity by heating.
The degree of autoagglutination of isolates in 0.1-10% CaCl₂ or 1% acriflavine hydrochloride solution closely related with serovars. Serovar B-I and B-Il showed marked autoagglutination while serovar A did not or much less in degree even if it occurred. The same phenomenon was also observed when heat treatment was given to the isolates suspended in 0.85% NaCl solution.
Serovar A is distributed all over Asian countries more widely with higher frequency as compared to serovar B.