Isolation, Identification and Antagonistic Effect of Rhizobacteria Associated with Coffee (Coffea arabica L.) Rhizosphere Against Coffee Berry Disease (Colletotrichum kahawae) Jimma, Ethiopia

Abstract

Coffee berry disease caused by fungus Colletotrichum kahawae, is considered as major disease of coffee in Ethiopia. Different control methods practiced at coffee producing farms and farmer levels in the country including chemical control. Hence, the use of chemical fungicide is causes environmental pollution and abortion of natural sustainability. However, the development of biological control helps to improve plant health, yield, reduce health risk and hazardous effects on environments have got great concern. Hereafter, this study was carried out to examine the antagonistic effects of rhizobacteria isolated from Arabica Coffee rhizosphere against Colletotrichum kahawae, that causes coffee berry disease, under in vitro and in vivo conditions. The soil sample used sources of bacteria were taken from Gera, Ela Dalle and around the JUCAVM campus. The isolation result showed that, total of 215 isolated from Gera (104), Ela dale (67) and JUCAVM campus (44) in ten different bacteria species on Kings B medium. The isolated bacteria were in-vitro tested by using CRD with three replications. Out of 215 isolated rhizobacteria antagonistic tested on Half Strength King’s B (HSKB) medium, 28 exhibited remarkable range of 8.2% – 91.3% C. kahawae radial growth inhibition and four rhizobacteria; Bacillus spp. (JU544) by 91.3%, Pseudomonas spp. (JU13) by 82.3%, Bacillus spp. (JU735 by 74.6%, and Micrococcus spp. (JU533) with 67% showed high inhibition percentage. High performed rhizobacteria were tested under in vivo condition against the fungal pathogen on detached green coffee berry, by applying the isolates at the same time of inoculation, 48 hours before and after inoculation of the pathogen. The results at both severity and incidence showed that Bacillus spp. (JU544) and Pseudomonas spp. (JU13) genera were the most effective that significantly reduced (p<0.0001) the radial culture growth of the pathogen when compared to the control, respectively. Furthermore, Bacillus spp. (JU544) and Pseudomonas spp. (JU13) genera consistently reduced disease severity and incidence when applied at the same time than applying before 48hrs and 48 hours after inoculation on detached coffee berries. However, the highest bio-control efficiency reduced disease severity and disease incidence was 89% and 76.7% when the coffee berry was treated with Bacillus spp. (JU544) at the same time with inoculation of the pathogen. Thus, considerable efforts should be devoted on isolation, identification of the plant growth promoting rhizobacteria and to evaluate the genera’s effectiveness against the coffee berry disease causing pathogen. In order to develop new microbial fungicides as alternative to control and fight berry anthracnose and as well as to formulate integrated disease management schedule and come up with strong recommendation. This study was conducted under laboratory conditions. Moreover, optimum concentration, application methods of rhizobacteria should be studied. Further conformation may be also important.