Histopathological study of resistance to cercospora beticola in sugar beet

Infection process including spore germination, penetration and intercellular development of Cercospora beticola in the mesophyll of immature and mature leaves of two resistant (FD0018 and HM1836) and a susceptible genotypes (236) of sugar beet were studied, in order to determine the relative importance of defense phenomena in pre and post-penetration stage of infection to the pathogen in sugar beet. The results indicated that pre-penetration stages had no importance in resistance because there was no significant difference between resistant and susceptible genotypes, but in endophytic phase some penetrating germ tubes in resistant genotype stopped in initial stages and did not develop to necrotic phase.