Abstract
The utilization of resistant Arabica coffee ( Coffea arabica ) varieties is considered as the most economical control for coffee berry disease (CBD) and coffee leaf rust (CLR) in Tanzania. The resistance levels of varieties at field and laboratory conditions were assessed through their phenotypic disease reaction response to CBD and CLR. In this study sixteen (16) compact hybrids of C. arabica plus four (4) standard cultivars were evaluated under a range of environmental conditions in on-station and on-farm trials in Tanzania. Also four (4) Colletotrichum kahawae strains of the pathogen responsible for CBD infection; 2010/1, 2010/2, 2006/7 and 2006/14, and Hemileia vastatrix uredospores were used to test the sixteen (16) hybrids through artificial inoculation under controlled conditions (temperatures between 19 to 22 oC, R. H. 100%). Results showed that a significant level of variability (P < 0.05) occurred between the sixteen (16) compacts, three (3) standard checks and N39 a commercial susceptible variety across trials. Compact genotype CVT14 (PNI086 x (N39 x Rume Sudan Selfed F 2 ) showed resistance to the four strains of C. kahawae and Hemileia vastatrix . Differential reactions on compact genotypes were found to C. kahawae and H. vastatrix strains existing in different coffee growing regions in Tanzania; genotypes CVT4 (PNI088 x (SL34 x HdT) x Kent x Rume Sudan) and CVT13 (PRO127 x (Blue Mountain Jamaica x Cioccie) x Rume Sudan) showed partial resistance to C. kahawae strains 2010/1, the genotypes were susceptible to strains 2010/2 but resistant to strains 2006/7 and 2006/14. This shows that host response reaction can be used as criteria for varietal assessment when evaluated at different locations.
Highlights
Coffee production in Tanzania is still constrained to a large extent by the ability of the growers to control coffee berry disease (CBD) and coffee leaf rust (CLR)
Differential reactions on compact genotypes were found to C. kahawae and H. vastatrix strains existing in different coffee growing regions in Tanzania; genotypes CVT4 (PNI088 x (SL34 x Hibrido de Timor (HdT)) x Kent x Rume Sudan) and CVT13 (PRO127 x (Blue Mountain Jamaica x Cioccie) x Rume Sudan) showed partial resistance to C. kahawae strains 2010/1, the genotypes were susceptible to strains 2010/2 but resistant to strains 2006/7 and 2006/14
Despite high level of pathogenicity of isolate 2011/1, C. kahawae isolates 2006/14, 2010/2, 2006/7 and 2010/1 were selected representing four ecosystem to test the reaction of the compact genotypes
Summary
Coffee production in Tanzania is still constrained to a large extent by the ability of the growers to control coffee berry disease (CBD) and coffee leaf rust (CLR). The varieties including N39, KP423, KP162 and H66 among others occupy over 80% of the total Tanzanian coffee acreage (Fernie, 1970; Robinson, 1964). They are protected against CBD and CLR by an intensive fungicide spray programme that accounts for up to 50% of the production costs (Gustave et al, 2007; Teri et al, 2004; Omondi et al, 2000). The fungicides are uneconomical and environmentally unsafe
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