Susceptibility of species of Juglans to pathovars of Xanthomonas campestris

Bacterial blight is considered one of the most serious diseases affecting t he genus Juglans. Artificial inoculations with Xanthomonas campestris pv. j uglandis were performed in the field by spraying seedlings Juglans cinerea, Juglans hindsii, Juglans mandshurica, Juglans nigra, Juglans regia and Jug lans sieboldiana. Juglans nigra, J. cinerea and J. sieboldiana proved to be the most resistant. The multiplication ability of Xanthomonas campestris p v. corylina, X. c. pv. juglandis, and X, c. pv. campestris ;was evaluated b y injecting 2-year-old seedling leaves of J. mandshurica, J. nigra and J. r egia. The bacterial growth was monitored in the infected tissue over 12 day s. Xanthomonas c. pv. juglandis exhibited a high growth rate and induced bl ack greasy spots in J. mandshurica and J. regia; X. c. pv. campestris grew in leaf tissues without inducing symptoms, X, c. pv. corylina showed a very low growth rate. None of the tested bacterial strains multiplied in the le aves of J. nigra. This confirms the results obtained in the field tests. Ju glans regia was the most susceptible among the walnut species tested.