Abstract:

By measuring the number of bacteria adsorbed on root surfaces and contained in roots of 2 eucalyptus clones with different extent in resistance to the bacterial wilt and a non-host species after inoculation with Ralstonia solanacearum and non-pathogenic Escherichia coli,it was found that the number of adsorption of R. solanacearum to the root surface of susceptible host was greater than that of the resistant hosts and non-host, the number of ingression of the pathogen to the root of susceptible host was greater than that of the resistant hosts but smaller than that of the non-host; the number of adsorption of pathogenic bacteria to susceptible eucalyptus root surface was greater than that of the non-pathogenic bacteria, the number of ingression of the pathogen to susceptible host root was greater or smaller than that of the non-pathogen depending on whether there were wounds on roots. During a period of 24 h after inoculation, the number of R. solanacearum both adsorbed on root surface and contained in root exhibited an increasing tendency in susceptible eucalyptus but a decline pattern in resistant host and non-host. Statistically, R. solanacearum demonstrated a certain degree of selectivity in terms of adsorption and ingression to host root, the selectivity, however, was of little biological significance since the pathogenic bacteria could adsorb to and ingress into the roots of resistant host and non-host in a great quantity, and non-pathogenic bacteria could also adsorb to and ingress into the root of eucalyptus in a great number. R. solanacearum did not show an evident recognition behavior to the root surface of eucalyptus.

Key words: eucalyptus, Ralstonia solanacearum, adsorption, ingression, nonhost, recognition