ABSTRACT
Diluted bacterial culture suspension is inoculated by the injection infiltration method in tobacco leaves with a hypodermic syringe. Different cultures may be inoculated in different interveinal sections of the same tobacco leaf. The cultures, which are plant pathogenic, produce quick necrosis hypersensitive reaction (HR) within 24 hours. Once the bacterium is isolated from the diseased plant material, it is necessary to know whether the isolated bacteria is the actual cause of the disease and is pathogenic. The method is based on the fact that only plant pathogenic bacteria are able to induce a HR in tobacco. Sometimes the HR is produced as early as 8 hours. Those isolates that gives an HR in tobacco plants are surely plant pathogenic bacterial isolates. Most of the plant pathogenic bacteria produce hypersensitive browning reactions on tobacco plants. The reaction of plant pathogenic bacteria, particularly Erwinia, on soft pear fruit is very quick.
