Serological difference between Erwinia herbicola strains of plant and human origin.

Fifty Erwinia herbicola isolates obtained from host plants were examined in an agglutination reaction with antiserum prepared against E. ananas (E. herbicola) strain CCM 2407 antigen of plant origin and with antiserum prepared against Enterobacter agglomerans strain CNCTC M 269 antigen of human origin. In tests with strain CCM 2407 antiserum, 56% isolates showed a positive reaction, while in tests with strain CNCTC M 269 antiserum only 14% isolates showed a positive reaction. Among E. herbicola isolates which showed a positive reaction with CCM 2407 antiserum 18% showed a positive reaction with the CNCTC M 269 antiserum too. Our results confirmed the serological heterogeneity of E. herbicola population. In spite of the difference in the origin of the two antigens used for the preparation of antisera (plant, human; Japan, Czech Republic) our results indicate that some of our E. herbicola strains and E. agglomerans strain CNCTC M 269 are serologically identical.

Influence of soil pH and calcium nutrition on resistance of alfalfa to bacterial and verticillium wilt.

Alfalfa plants of a resistant, a susceptible and a highly susceptible strains were grown in unlimed soil at pH 5.8 and in limed one at pH 6.9 and inoculated by the pathogens of vascular wilt, Corynebacterium insidiosum and Verticillium albo-atrum. Two types of liming were performed: 1) before inoculation and 2) after inoculation. Liming of the soil led to an increase in number of resistant plants. In susceptible plants the external symptoms of disease on the plant tops were delayed or alleviated. This phenomen was more conspicuous with Verticillium wilt than with bacterial wilt. The favourable effect of liming was less distinct in resistant strains than in susceptible ones. For an increase in resistance, post-infection liming of the soil was more effective in the case of bacterial wilt, while pre-infection liming provided the best results in the Verticillium wilt. The nitrogen content in the dry matter of roots from plants grown in limed soil was higher by more than a quarter as compared to roots from plants growing in unlimed soil.