Colonial Growth and Virulence through Water Culture Inoculation of Juvenile Shoots with Eucalypt Bacterial Wilt Pathogens from Distinct Origins

It was found that 12 Ralstonia solanacearum isolates from distinct origins were obviously different in colonial growth and virulence through water culture inoculation of eucalypt juvenile shoots,but the colonial growth and virulence did not exhibit relationship.The virulence significantly increased with the concentration of pathogen solution.However,4 eucalypt clones tested did not show marked difference in susceptibility to the bacterial wilt pathogen.Most of the colony growth on plate occurred in the first 4 days after inoculation,with the average diameter ranging from 3.53 to 27.68 mm on the 4th day.Further analysis showed that if two pathogen isolates with the strongest and weakest virulence respectively were excluded,the remaining isolates with different origins became similar in virulence.This implied that under the same or similar environmental and climatic conditions,most of young eucalypt stands in distant regions or places have the likeness in incurring bacterial wilt,while the rest may severely be damaged by certain isolates with strong virulence.