The Potential of Fungi as Bio-Control Agents in Managing Colletotrichum Kahawae In Kenya

Colletotrichum kahawae is a causative fungal agent of Coffee Berry Disease (CBD) that negatively affects coffee production. Its control relies on use of resistant varieties and chemical control. Fungicides used in control of CBD are costly and pose a risk to environment and health. The study was aimed at assessing the possible antagonistic potential of fungal isolates against Colletotrichum kahawae in in vitro conditions. Five isolates were used; one isolate was collected from berries while the rest were collected from soil. Testing for antagonism against Colletorichum kahawae was done by co-culturing the isolates on Potato Dextrose Agar. The degree of antagonism was determined by measuring and comparing the radial growth of pathogen with the bio-agent against the control. Out of the five isolates tested against C. kahawae, three isolates Fusarium proliferetum, Penicillium and Fusarium ceraneasum significantly inhibited test pathogen growth at 60%, 55% and 45.45%, respectively. The other isolates, Fumigatus aspergillus and Chaetomium perithecia showed inhibition of growth at 40% and 18.18% respectively. It was concluded that there is potential of using fungi as bio control of the coffee berry disease.

The dark side of shade: How microclimates drive the epidemiological mechanisms of coffee berry disease

Coffee berry disease (CBD) can cause significant coffee yield losses along with major income losses for African smallholders. Although these farmers cannot afford to purchase pesticides to control the disease, agroecological solutions have rarely been investigated, and how epidemiological mechanisms are linked to the environment of the coffee tree and the plot remains unclear. Agroforestry systems are a promising agroecological option, but the effect of shade on CBD regulation is the subject of debate, and the use of plant species diversity remains uncertain. Here, we address how shade affects epidemiological mechanisms by modifying the microclimate. For this purpose, we developed a mechanistic susceptible-exposed-infectious-removed (SEIR) model, and used a Bayesian framework to infer the epidemiological parameters against microclimatic covariates. We show that shade has opposing effects on different epidemiological mechanisms. Specifically, shade can limit disease dynamics by reducing disease transmission while simultaneously promoting disease dynamics by reducing the latent period of the pathogen. However, in full sun, efficient disease transmission compensates for long latent periods. As a result, the balances between microclimatic variables can counterbalance the epidemiological rates, which can dramatically alter the fate of epidemics in shade versus full sun conditions. We propose research avenues to help design cost- and environmentally effective management strategies for CBD that are notably based on the functional traits of shade trees that could hamper CBD dispersal.

Incidence and severity of major diseases of coffee in highland of eastern Ethiopia

This study was conducted with the objective to assess the incidence and severity of coffee berry disease (CBD) and coffee leaf rust (CLR) in the highland of Eastern Ethiopia. In the east Hararge Zone of Eastern Ethiopia, coffee was grown by 331,651 holders on 7,584 ha with a production output of 3,722 tons and a yield of 0.5 ton/ha in 2017. Bedeno is the leading coffee producer district in the Zone followed by Melka-ballo, Deder and Meta districts. In Bedeno, coffee is mainly grown in altitudes ranging from 1690 to 2260 masl. Coffeeberry disease and leaf rust are the two major diseases of coffee in the area. A total of 34 representative coffee farms at nine study sites (3-4 coffee farms at the interval of 3-5 kilometers) were selected through discussion with Bedeno district’s coffee experts. The study sites were selected using sequential sampling techniques through discussions with the district’s coffee experts. Incidence of coffee berry disease and leaf rust was determined as percentage of diseased trees. Disease severity was determined as percentage of diseased coffee berries per plot. Data were analyzed using descriptive statistics. The result of this study revealed the incidence of CBD in Bedeno district ranged from 30.0 to 93.3% with a mean of 70.19%. The severity of the CBD was from 13.3% to 44.4% with an average severity of 28.53%. Both incidence and severity of CBD were high at Barkalle followed by Barakat and Hindhessa areas. On the other hand, the incidence of coffee leaf rust varied from 18.9 to 87.4% with a mean of 52.7%. The high mean incidence of CLR at highland areas of eastern Ethiopia is clear evidence for the occurrence of climate change in the area. Hence, it is advisable to introduce improved coffee varieties that are resistant to coffee berry disease and leaf rust for production in the area. Training farmers to implement proper cultural disease management practices such as prunning and sucker management will also help alleviate the constraint.

Pathological, Morphological, Cytogenomic, Biochemical and Molecular Data Support the Distinction between Colletotrichum cigarro comb. et stat. nov. and Colletotrichum kahawae

The genus Colletotrichum has witnessed tremendous variations over the years in the number of species recognized, ranging from 11 to several hundreds. Host-specific fungal species, once the rule, are now the exception, with polyphagous behavior regarded as normal in this genus. The species Colletotrichum kahawae was created to accommodate the pathogens that have the unique ability to infect green developing coffee berries causing the devastating Coffee Berry Disease in Africa, but its close phylogenetic relationship to a polyphagous group of fungi in the C. gloeosporioides species complex led some researchers to regard these pathogens as members of a wider species. In this work we combine pathological, morphological, cytogenomic, biochemical, and molecular data of a comprehensive set of phylogenetically-related isolates to show that the Coffee Berry Disease pathogen forms a separate species, C. kahawae, and also to assign the closely related fungi, previously in C. kahawae subsp. cigarro, to a new species, C. cigarro comb. et stat. nov. This taxonomic clarification provides an opportunity to link phylogeny and functional biology, and additionally enables a much-needed tool for plant pathology and agronomy, associating exclusively C. kahawae to the Coffee Berry Disease pathogen.