Characterization and virulence determination of Colletotrichum kahawae isolates from Gidami, Western Ethiopia

Abstract

Coffee is one of the most essential crops that generate income for Ethiopian economic growth. However, its production faced with many factors primarily biotic entities. Among these, the fungal pathogen /Colletotrichum kahawae/ that induce coffee berry disease (CBD) is the main constraint of coffee production in the country. The pathogen is a very specialized and infects the green berries/fiscal par/which diminishes the income gained from it and disturbs the country’s economy in general and the producers in particular. Regarding to the disease level and related factors, little information is available in Western Ethiopia. Hence, this study was initiated to assess the magnitude of CBD in coffee fields, to characterize and evaluate the virulence of C. kahawae isolates from the study areas of Gidami district. Assessment was done in 9 selected kebeles of 45 total farms starting from July 2017. The results indicated that CBD was prevalence in all assessed areas with the range of 66% to 86% and 16% to 50% disease incidence and severity index (SI), respectively. The highest CBD intensity was observed in higher altitude with a significant positive correlation between disease incidence (r = 0.61) and severity (r = 0.55). Macro and microscopic characterization results revealed isolates diversity in terms of colony color, density, mycelia growth rate and conidial production. Moreover, mycelia growth rate differs significantly (p < 0.001) in the range between 2.2 to 4.3 mm/24 hrs. Similarly, the sporulation capacity widely ranged from 186.1 to 572.3 spores/ml. This were strongly agreed with the virulence test that revealed significant variation (p < 0.001) among isolates and infection percentage also ranged between 34.8% and 88.7%. In all, the study was not only showed the CBD is very important disease of coffee in the study area but also determines the virulence disparity among isolates. To be honest, the diversity/identity of C. kahawae isolates should be confirmed using more other reliable methods thru including additional sample areas as well.

Influence of altitudes on the cultural and morphological variation of Colletotrichum kahawae isolates, the causal agent of coffee berry disease in the West Region of Cameroon

“…Kilimbo et al (2013) and Emana (2014) also conducted a similar study in Tanzania and Ethiopia, respectively and observed a growth rate of C. kahawae ranging from 5.0 to 5.5 mm/day on PDA. However, recent reports recorded a relatively lower growth rate of C. kahawae isolates ranging from 2.2 to 4.30 mm/day on PDA (Amare et al, 2021;Zenebe et al, 2021). Differences in growth rate observed among the isolates of C. kahawae in the present study are probably due to prevailing environmental conditions in the respective altitude of origin of isolates.…”

“…The morphological characteristics of C. kahawae were observed based on their conidia shape and size, they varied significantly among the isolates as also noted in other studies (Kilimbo et al, 2013;Emana, 2014;Bersisa et al, 2018;Alemu et al, 2020;Amare et al, 2021;Zenebe et al, 2021). Isolates CBDBHa1, CBDBHa2 and CBDBHa3 from the high altitude of the Bamboutos division and CBDBMa1 and CBDBMa2 isolated from the medium altitude of the same division produced cylindrical shaped conidia with acute at one end and round at the other end to sometime round at both ends.…”

“…These values fall within the interval described by Amare et al (2021) for conidia production that ranged from 182.25 to 432.92 × 10 4 conidia/ml. Similarly, Zenebe et al (2021) also reported the variation in the number of conidia production ranged from 186.10 to 572.30 × 10 4 conidia/ml. In addition, Emana (2014) and Bersisa et al (2018) also recorded relatively lower conidia production on PDA ranging between 39.53 to 260.85 × 10 4 conidia/ml and 75 to 144 × 10 4 conidia/ml, respectively.…”

“…Coffee berry disease (CBD) caused by Colletotrichum kahawae, is the most devastating threat to Coffea arabica L. production in Africa. CBD broke out in Kenya in 1922 (Hindorf and Omondi, 2011) and later spread to all major coffee-producing areas like Angola (1930), Cameroon (1955to 1957, Uganda (1959), Tanzania (1964) and Ethiopia (1971) (Hindorf and Omondi, 2011;Zenebe et al, 2021). The impact of this disease varies with location and period of year depending on the management practices undertaken, the rainfall pattern and the altitude (Belachew and Teferi, 2015;Garedew et al, 2017).…”

“…According to Van der Vossen et al (2015) a good understanding of the biology of C. kahawae could lead to the development of coffee varieties with sufficient disease resistance and disease management strategies. Researched have been conducted across the globe indicating the variation among C. kahawae isolates through morphocultural characteristics (Bersisa et al, 2018;Alemu et al, 2020;Amare et al, 2021;Zenebe et al, 2021). Derso and Waller (2003) reported the presence of several morphological and cultural characteristics within C. kahawae isolates in Ethiopia and indicated that, it would be useful to look at a profile of several isolates from widely differing coffee types existing in the country.…”