Host Range And Host (Un)Specificity Of Different Isolates Of Polymyxa betae
Five soil samples were taken from sugar beet growing areas in France (3), England (1) and Czech Republic (1). Sugar beet, Chenopodium album, C. murale, C. ficifolium, Portulaca oleracea, and Amaranthus retroflexus as possible hosts of specific formae speciales were sown in these samples. After six weeks roots of baiting plants were checked for the presence of P. betae cystosori. If they were not found every two weeks other plants were checked. Roots containing cystosori were harvested and homogenized in water. The homogenates were used to inoculate the same plants host in sand cultures. Using this method we obtained P. betae isolates from sugar beet and C. murale from all soil samples and two isolates from C. album. Roots of plants were used for the enrichment of P. betae population in sand. Then all host species were sown in these sands and roots of plants were checked as described above. Sugar beet and C. murale were infected in all soils. C. ficifolium and C. album were infected in three soils; A. retroflexus in one soil and P. oleracea has never been infected. On the contrary, after the enrichment of population of given isolate in sand all other hosts were always infected with two exceptional cases of A. retroflexus only. It means that there is almost no host specificity of different isolates. In different trials seeds of potential host species were sown into soil containing P. betae. The procedure was similar as described above. Some new host of P. betae were found.