DISEASE RESISTANCE OF EUCALYPT CLONES TO CERATOCYSTIS MANGINECANS

Abstract

Ceratocystis manginecans is causing serious damage to Eucalyptus plantations in Vietnam. When the stems of 8-month-old ramets of two widely-planted Eucalyptus clones were inoculated with nine C. manginecans isolates in a nursery trial, all caused disease. Using the same methodology, the two most pathogenic isolates were used to rank the resistance of 18 Eucalyptus clones. Significant (p < 0.001) differences among clones were observed for both lesion length and percentage mortality, 90 days after inoculation. Three Eucalyptus hybrid clones and seven E. urophylla clones were highly resistant, with mean lesion length from 0.99 to 2.75 cm and mortality ranging from 0 to 5.0%. The remaining eight clones, including the two clones used to screen the C. manginecans isolates, displayed low to moderate resistance with mean lesion length exceeding 5 cm and mortality ranging from 15.0 to 41.7%. This suggests that there are opportunities to deploy Eucalyptus hybrid and E. urophylla clones, resistant to C. manginecans, to enhance disease resistance through crossing among resistant genotypes.