Abstract

Eighteen clones of coffee rust differentials were used to characterize rust races prevailing in the coffee growing areas in Arusha, Kilimanjaro, Mara, Bukoba, Kigoma, Mbeya and Ruvuma regions. The results showed the presence of seven new Hemileia vastatrix races causative agent for coffee leaf rust (CLR) in the surveyed coffee growing areas. The races were: XLI (v2, 5, 8), XLII (v2, 5, 7, 8 or v2, 5, 7, 8, 9), XV (v4, 5), XXX (v5, 8), XXXIII (v5, 7 or v5, 7, 9), XXXIV (v2, 5, 7 or v2, 5, 7, 9), XXXIX (v2, 4, 5, 6, 7, 8, 9). Four strains of Colletotrichum kahawae originating from 4 coffee ecosystems were used to test their level of pathogenicity on 16 compact coffee genotypes, Ctr088 and commercial variety N39. The four C. kahawae strains were less pathogenic to six compact coffee genotypes; CVT2, CVT4, CVT5, CVT7, CVT8 and CVT13, completely nil pathogenic to Ctr088, but significantly highly (P < 0.05) pathogenic to N39. Coffee genotype Ctr088 was confirmed to be a potential donor of developing coffee berry disease (CBD) varieties with durable resistance. Differential interaction between the compact genotypes and the four C. kahawae strains needs further investigation.

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