EFFECT OF ROOT INJURY ON LESION DEVELOPMENT OF CARAWAY ROOTS INFECTEDBY MYCOCENTROSPORA-ACERINA

The effect of injury on disease incidence, incubation period and lesio n development rate on caraway roots by Mycocentrospora acerina was stu died in three laboratory experiments. After inoculation with M. acerin a, disease incidence of injured roots was significantly (P < 0.001) hi gher than of non-injured roots. The incubation period of M. acerina wa s significantly (P < 0.001) shorter on injured roots than on non-injur ed roots. The incubation period shortened with increasing root injury level. Younger injured roots tended to be more resistant to M. acerina infection than older injured roots, expressed by longer incubation pe riods. The lesion development rate was, on average, higher on heavily injured roots than on non-or slightly injured roots. The lesion develo pment rate remained fairly constant after the first emergence of the s ymptoms on the caraway root, until the whole root was colonized. Caraw ay roots carefully dug up in autumn frequently showed injuries enablin g M. acerina to penetrate the roots. However, the correlation between root injury and root rot after cold storage was weak. Injury of roots had a stimulating effect on infection and development of M. acerina, b ut roots without wounds could be infected too. Some relevant field obs ervations are discussed.