Assessment And Characterization Of Coffee Berry Disease (Colletotrichum Kahawae) And Resistance Evaluation Of Gurage Coffee Accessions

Abstract

Arabica Coffee is an important crop in the national economy of Ethiopia. Coffee berry disease (CBD), coffee wilt disease (CLD) and coffee leaf rust (CLR) are the most important coffee diseases in the country. Development of coffee cultivars for different localities having a character of diseases resistant, high yielding and quality coffee is important. Previous research works have little effort to provide varieties that are suitable for Gurage zone southern parts of Ethiopia in addition to the little information available regarding the extent of CBD and related factors in this area. Hence, this study was carried out to assess the magnitude and extent of CBD, characterize the virulence of C. kahawae isolates and evaluate Gurage coffee accessions against CBD. The survey was conducted in three districts of Gurage zone including Cheha, Ezha and Enemorina Ener during July to August 2017. Attach Berry Test and Detach Berry Test evaluations of Gurage coffee accessions were conducted under field and laboratory condition in Randomized Complete Block Design and Completely Randomized Design, respectively. The survey result revealed that CBD was prevalent in all the assessed areas that range from 86.66 to 100% and 38.89 to 59.44% for Disease Incidence and Percent Severity Index, respectively. Out of 33 sample 13 representative C. kahawae isolates from the survey areas and one Gera isolate were isolated from infected green coffee berry which showed significant variations in their Morphological characteristics and pathogenicity. Mean radial colony growth rate of isolate showed significant variation (p<0.001) with the range of 2.67 to 4.08 mm/24hrs on PDA in EZA and CA1 isolates, respectively. Conidial size also showed significant difference (p<0.001) in the range of 5 to 6.04 and 9.24 to 10.0 µm in width and length, respectively. Similarly, conidia production varied from 182.25 to 432.92×104conidia/ml of isolate EK1 and EZD, respectively. All isolates were found to be pathogenic to Arabica coffee with highly significant variation (P < 0.01) and infection percentage in the ranges of 45.83 to 68.06%. Gurage coffee accessions Gu-18, Gu-1 and Gu-4 had lower CBD infection level in both field and laboratory experiment, which was 5.4, 8.29 and 11.37 and 32.5, 45.0 and 25.8 %, respectively. Aggressive isolate EZD should be used for screening of coffee variety for CBD resistance evaluations. Future research should focus on evaluating the promising Gurage coffee accessions in seedling inoculation test and in multilocation field trials for several years.