DEVELOPMENT OF HEMILEIA-VASTATRIX IN COFFEE PLANTS WITH GENETIC OR INDUCED RESISTANCE

Systemic resistance to coffee rust (Hemileia vastatrix) was induced in susceptible cv. 'Mundo Novo' by spraying foliage with a yeast filtrat e. The stages of fungal development were compared in leaves of untreat ed (MN), induced 'Mundo Novo' (MN-I) and coffee rust resistant segrega nts of the hybrid 'Sarchimor' (Sch). Development of H. vastatrix was o bserved at intervals of 228 h after inoculation. The expression of res istance was detected 48-72 h after inoculation. In Sch, it occurred at the one haustorial mother cell (HMC) stage, whereas in MN-I, it occur red at the 2nd HMC stage. In Sch the majority of aborted colonies were associated with necrotic host cells, and the collapsed fungal hyphae exhibited a yellow autofluorescence which was observed in necrotic cel ls of the host. In MN-I, 80% of the colonies could not be visualized 7 2 h after inoculation and host cells at the infection sites were not n ecrotic.