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Key message The study unraveled the dynamics of mechanisms causing biennality in coffee, its consequences for competition for carbon and nitrogen and suggests means of adequately managing the problem. Imbalance in fruit load and branch growth plays a role in the occurrence of biennial bean production patterns in coffee ( Coffea arabica L.). Effects of fruit load manipulations were studied in two field experiments in the Jimma region, Ethiopia, over two consecutive years. Treatments consisted of reducing fruit loads in the pinhead stage to 25, 50, 75 % and controls keeping 100 % of the fruits per tree (treatments coded T25 through T100). Treatments were applied in the first year only. Branch growth and the formation of new leaves, drop of old leaves, light saturated rate of leaf photosynthesis ( A max ), nitrogen content of leaves on selected branches, as well yield and bean characteristics were evaluated throughout the experimental period. The study revealed that branch growth, and leaf N content per unit leaf area, N a , were inversely associated with fruit load, whereas loss of basal leaves on branches increased with fruit load and over time. A max was strongly and linearly associated with N a and declined with increase in fruit load. In the year of treatment green bean yield increased with fruit load, but in the second year the reverse was true. On aggregate over 2 years, treatment T25 and T50 out yielded treatments T75 and T100. Fruit thinning shifted the bean size distribution to larger sizes. In conclusion, fruit thinning modulated the balance between branch growth and fruit development. Thus enhanced branch growth, improved bean size and stabilized yield over years.

Mother-to-child transmission (MTCT) of human immune deficiency virus (HIV) is the infection of baby by HIV that originated from an HIV-positive mother during pregnancy and breast feeding. Without intervention, the transmission rate of HIV ranges from 15-45%, which can be reduced to below 5% with effective intervention. In Ethiopia, the final mother-to-child transmission rate was 15% in 2016, which was much higher than the target of the country to reduce transmission to lower than 5% by 2020. The study aims to identify determinants of transmission of HIV from mother to child in the West Shewa Zone. An unmatched case-control study, among children less than 5 years who tested HIV positive and negative, at the end of PMTC follow-up, N=96 (24 cases, 72 controls) was conducted during June to August 2019, focusing on PCR done during the last 2 years (June 2017 to July 2019), in public hospitals. Data were collected using a structured questionnaire and data abstraction forms from mothers of exposed infants, medical records of mothers and children. The majority of cases (17, 70.8%) were not included in the option B+ program, but only 11.1% of controls were not included. Home delivery (adjusted odds ratio (AOR)=6.047, confidence interval (CI)=1.549-29.230), non-inclusion into option B+ (AOR=18.0, 95% CI=5.0-68.1), and partner non-involvement to HIV care (AOR=7.3, 95% CI=1.14-37.459) had higher odds of transmitting HIV, while a mother-to-mother support program decreases the chance of transmission by 86.5% (AOR=0.135, 95% CI=0.11-0.396) when compared to their counterparts. Mother-to-mother support programs have a protective effect, while non-inclusion to option B+, partner non-involvement in HIV care, home delivery, and poor antenatal care (ANC) practices were determinant factors of HIV transmission from mother to child.

The coffee species Coffea arabica is facing numerous challenges regarding climate change, pests and disease pressure. Improved varieties will be part of the solution. Making optimal use of the scarce genetic diversity of the species is hence essential. In this paper, we present the first study of C. arabica genetic diversity covering its complete native habitat in Ethiopia together with its main domestication centers: Yemen and Hararghe region in Ethiopia. All in all, 555 samples were analyzed with a set of Single Sequence Repeat markers. Through admixture genetic analysis, six clusters were identified. A total of two “Core Ethiopian” clusters did not participate in the domestication of the species. There were four clusters that were part of the “Domestication Pathway” of C. arabica. The first one was named “Ethiopian Legacy” as it represents the genetic link between “Core Ethiopia” and the “Domestication Pathway” in Yemen and Hararghe. The geographic origin of this cluster in Ethiopia was the south of Ethiopia, namely Gedio, Guji and Sidama, which hence appears as the source of coffee seeds that led to the domestication of C. arabica. In Yemen, in addition to the “Ethiopian Legacy” cluster, we confirmed the “Typica/Bourbon” and “New-Yemen” clusters. In Hararghe, the “Harrar” cluster, never described before, likely originates from a re-introduction of domesticated coffee from Yemen into this region of Ethiopia. Cultivated varieties around the world today originate from the “Ethiopian Legacy” and “Typica/Bourbon” clusters and but none are related to the “new-Yemen” and “Harrar” clusters. Implications for breeding strategies are discussed.

The study examined the physical and chemical characteristics of Kafa Biosphere Reserve Forest coffees, collecting 54 georeferenced samples from various zones and plots within the forests. Samples were processed, cleaned, and ground, and chemical contents were determined using high-performance liquid chromatography. Analysis of variance, descriptive statistics, principal component, multiple factors, and hierarchical cluster analysis were applied to the data collected in a three-stage balanced nested design. The district difference did not significantly affect bean physical and chemical contents, but it did affect fruit physical qualities. Forest zonation did not affect these attributes. The effect of forest plotting was significant on the chlorogenic acid content, fruit width and thickness, and seed length. The descriptive statistics results revealed significant variations in coffee chemical compounds across different sampling locations. The principal component analysis revealed that 61.97% of variation in forest coffee chemical and physical attributes is influenced by factors like chlorogenic acid content and fruit and seed width. Multiple-factor analysis showed a tendency for a relationship to be observed between the elevation gradient with nicotinic acid and the measured physical attributes of coffee samples. Nicotinic acid tends to increase with elevation, whereas coffee fruit and seed sizes become larger with reduced nicotinic acid content at a decreasing elevation. Cluster analysis categorizes the samples into three major clusters. The study confirms that the chemical and physical properties of coffee fruit and beans vary more significantly in smaller sampling categories, suggesting further investigation.

A comprehensive examination of the physical and cup quality of Kafa Biosphere Reserve coffees was essential to identify the inherent qualities of the coffees in connection with the area’s soil physical and chemical characteristics. As a result, preliminary coffee quality data was acquired from bean physical and cup quality examination of coffees derived through a three-stage nested design combining districts (Gimbo, Gawata, and Decha), coffee production systems (forest, semiforest, and garden), and coffee processing methods (wet, semiwet, and dry). Representative soil samples were collected according to the sampling structure and analyzed following the standard procedures. Multiple factor analysis and Pearson’s correlation coefficient analysis were applied to the collected data. According to the results of multiple factor analysis, the Gimbo and Decha districts are not significantly different from each other in terms of coffee quality. However, they are substantially different from the Gawata district in terms of coffee quality. Similarly, within each district, there are no clear differences in coffee production systems. However, the production systems of districts varied significantly. The coffee processing method had a pronounced effect on the overall quality and preliminary grade, physical and raw quality variables of coffee. Screen retention (14) was correlated with soil iron, but it was related negatively to boron and sodium contents. A significant and positive relationship was observed between green coffee bean moisture content and soil potassium, calcium, magnesium, boron, sodium, organic carbon, silicon content, and soil pH. A positive and significant relationship between soil molybdenum and the coffee quality variable was observed across the studied districts whereas most soil micronutrients, specifically, zinc, sulfur, and manganese, were significantly and negatively related to the organoleptic qualities of the coffees. Further investigation that includes the effects of elevation is recommended in future studies.

A comprehensive physical and cup quality assessment of coffee (Coffea arabica L.) has not yet been conducted on Kafa Biosphere Reserve coffees. Hence, the influence of location, production systems, and processing methods on coffee bean physical and sensorial qualities were studied to identify the inherent qualities and suitable preparation methods for the improvement of bean physical and organoleptic qualities. In a three‐stage nested design, factors such as location (Gimbo, Gawata, and Decha districts), coffee production system (forest, semiforest, and garden), and processing method (wet, semiwet, and dry) were considered. Preliminary coffee quality assessment data were gathered from bean physical and cup quality analyses of coffee obtained from the combination of the three factors. An ANOVA was conducted on preliminary coffee quality data. The result of the ANOVA showed that location and production system effects were significant only on bean moisture content (P < .01) and acidity (P < .05), respectively. The processing effect had a significant effect on bean moisture (P < .01), odor (P < .001), raw (P < .01), and preliminary grade (P < .05). Better coffee quality was maintained in the dry coffee processing method within the recommended moisture content. Forest and semiforest coffees respond poorly in odor and overall raw coffee quality when treated with wet and semiwet processing methods. Hence, to attain a better quality of coffee, rather than proper harvesting procedures, more emphasis should be given to choosing proper processing methods. Further investigation that includes the effects of elevation gradient is recommended. Core Ideas Coffee production location differences have a significant effect on bean moisture content. Coffee production system effects can significantly affect the acidity of coffee cup quality. Coffee processing had a significant effect on bean moisture, odor, raw, and grade. The dry coffee processing method maintained cup quality of coffee better than wet methods.

Coffea arabica is native to the Afromontane forests of southwestern Ethiopia, the leading African country in Arabica coffee production. The intensity of coffee leaf rust (CLR), a fungal disease of growing concern to coffee farmers, was assessed in eight coffee berry disease-resistant C. arabica varieties planted at three different altitudes. Disease variables assessed were CLR prevalence (percent of infected plants), incidence (percent rusted leaves) and severity (percent leaf area affected) at four times within a year (Nov, Jan, Apr and Jun). The intensity of CLR epidemics was highest at the lowland and lowest at the highland location. We hypothesize that inoculum may be limited by cooling conditions that negatively affects fungal sporulation. CLR intensity was highest at harvest time (Nov) and decreased during the following dry season, reaching zero values in Apr and Jun. All coffee varieties were similarly susceptible to CLR. Our data suggest that more efforts should be employed by breeders to develop CLR-resistant coffee varieties, and that shifting cultivation from lower to higher altitudes may contribute to achieve to higher yields due to lower impact of CLR epidemics.

The coffee species Coffea arabica is facing numerous challenges regarding climate change, pests and disease pressure. Improved varieties will be part of the solution. Making optimal use of the scarce genetic diversity of the species is hence essential. In this paper, we present the first study of C. arabica genetic diversity covering its complete native habitat in Ethiopia together with its main domestication centers: Yemen and Hararghe region in Ethiopia. All in all, 555 samples were analyzed with a set of Single Sequence Repeat markers. Through admixture genetic analysis, six clusters were identified. A total of two \"Core Ethiopian\" clusters did not participate in the domestication of the species. There were four clusters that were part of the \"Domestication Pathway\" of C. arabica. The first one was named \"Ethiopian Legacy\" as it represents the genetic link between \"Core Ethiopia\" and the \"Domestication Pathway\" in Yemen and Hararghe. The geographic origin of this cluster in Ethiopia was the south of Ethiopia, namely Gedio, Guji and Sidama, which hence appears as the source of coffee seeds that led to the domestication of C. arabica. In Yemen, in addition to the \"Ethiopian Legacy\" cluster, we confirmed the \"Typica/Bourbon\" and \"New-Yemen\" clusters. In Hararghe, the \"Harrar\" cluster, never described before, likely originates from a re-introduction of domesticated coffee from Yemen into this region of Ethiopia. Cultivated varieties around the world today originate from the \"Ethiopian Legacy\" and \"Typica/Bourbon\" clusters and but none are related to the \"new-Yemen\" and \"Harrar\" clusters. Implications for breeding strategies are discussed.

Coffee (Coffea arabica L.) bean production and quality are determined by a diversity of interacting factors (e.g. shade, nitrogen, crop traits). Bean yield increases with increase in radiation, but adequate fertilizer supplies are needed to sustain the productivity. This thesis analysed coffee tree growth, bean production and bean quality in relation to different degrees of exposure to radiation and nitrogen supply. Growth of leaves and branches and properties of leaves such as specific leaf area, nitrogen content per unit leaf area and light-saturated rate of photosynthesis were determined. Radiation interception and nitrogen uptake were also determined as were radiation use efficiency and apparent nitrogen recovery. Tree biomass and coffee bean yield responded positively to both radiation and nitrogen supply. Abundant bean yield to the detriment of vegetative growth, however, resulted in biennial bearing in coffee trees. Effects of fruit load on coffee tree growth and productivity were studied for two consecutive years and the result showed that competition between fruit growth and vegetative growth predisposed the trees for biennial bearing. Reduced vegetative growth when fruit load is high reduces the number of flower bearing nodes and hence yields in the next season. Coffee quality is a sum of favourable characteristics that satisfies requirements of different actors in the coffee chain and is the factor determining the price on the coffee market. This study has also examined coffee quality attributes in relation to radiation and nitrogen, fruit load manipulation, and genotype by environment (different altitudes) interactions. The result indicated that factors and conditions that support non-limiting supply of resources for bean to grow and a sufficient long period of maturation promote coffee bean quality. Overall, the study gained further understanding of coffee tree growth, yield and bean quality responses to aforementioned factors and explored traits that underlie the patterns. Further works are required to use the traits and describe the behaviour of coffee trees in different agroecosystems.