OCCURRENCE OF BACILLUS POLYMYXA (PRAZ.) MIG. IN ALBERTA SOILS WITH SPECIAL REFERENCE TO ITS PATHOGENICITY ON POTATO TUBERS

Abstract

The spore-forming bacterium, Bacillus polymyxa, was found to occur widely in Alberta soils. All isolates obtained from the soil, together with several from other sources, proved capable of rotting potato tubers when introduced through wounds under conditions of abundant moisture and high temperature.In these studies pure cultures of Bacillus polymyxa rotted potato slices at temperatures from 20 °C. to 45 °C. and whole tubers at temperatures from 30 °C. to 45 °C. but caused no damage below the minimum temperatures mentioned.Though potato tubers and other vegetables that are formed in the soil probably often come in contact with Bacillus polymyxa, they are not likely to be rotted by it except when temperature and other factors are favourable. In general, soil temperatures in the field in Alberta are not conducive to the decay of potatoes by this organism, but those near the soil surface may on occasion reach favourable levels. The fact that B. polymyxa can be isolated quite frequently from rotted stored potatoes indicates that it is of some importance as a cause of decay in harvested potatoes. If, however, recommended storage temperatures are maintained in the storage quarters no damage from this organism should occur there.