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COCE- Wild Arabica Coffee Ecophysiological

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Project log

Taye Kufa
added 4 research items
The study focused on assessing soil physical properties under natural coffee forest ecosystems in southeast and southwest Ethiopia. For this, the Harenna, Berhane-Kontir, Bonga and Yayu forest coffee soils were collected from three sub-sites and two soil depth ranges at each area. Hence, a total of 24 soil samples were analyzed for major soil physical properties using the standard procedures. The results depicted significant differences among the coffee forests in soil texture particles (silt and sand), bulk density, soil moisture content, water holding capacity, permanent wilting point and available water holding capacity. The proportions of silt followed the order of Berhane-Kontir,Bonga,Yayu and Harenna soils. In contrast, the highest sand and clay contents were from Yayu and Harenna soils, respectively, possibly reflecting their variations in soil weathering process and parent materials, among others. Likewise, there were significant differences between soil depths in most soil physical parameters. In contrast to the increased clay and available water content, the silt and sand particles declined with the decrease in depth, indicating the more vulnerability of forest soils to erosion loss. The results also depicted that clay was negatively correlated with silt particles at all study areas. In contrast, the association between soil water contents at field capacity and permanent wilting point was direct and highly significant at most locations. In conclusions, the findings showed considerable site-specific variations in major soil physical properties and provided soil quality evidences for knowing and promoting natural coffee forest habitats in Ethiopia and elsewhere.
Root characteristics of coffee seedlings were studied with the main objective to compare the variations among twelve Coffea arabica germplasm accessions under contrasting nursery environments at Jimma Research Center, southwest Ethiopia. Coffee seedlings from four wild coffee populations, namely, Harenna, Bonga, Berhane-Kontir and Yayu were ex-situ established under common nursery settings. The treatments included coffee germplasm accessions, shadings (moderate shade and full sunlight) and irrigation levels (well-watered and water-stressed). One-year-old coffee seedlings were used to record root growth traits from five central seedlings per plot and the data were analyzed using SAS software. Coffee accessions significantly differed in most root characteristics. The longest and shortest lateral roots were obtained from Yayu and Harenna seedlings, respectively. Berhane-Kontir accessions had significantly the lowest root volume as opposed to the highest value for the Harenna seedlings. Significantly higher root dry biomass was obtained from unshaded than from shaded seedlings. The difference between watering regimes was also significant for root dry biomass and it was higher for water-stressed than for well-irrigated seedlings. Coffee accessions were significantly differed in root proliferation and dry biomass and consequently, the lowest and highest average values were obtained from Berhane-Kontir and Harenna seedlings, respectively. The Harenna seedlings had a higher root mass than the others, particularly the Berhane-Kontir accessions. The ratios of root to shoot dry biomass of the seedlings were significantly differed among coffee accessions, but not between shade and irrigation levels. The significantly lowest and highest root to shoot values was determined for the Berhane-Kontir and Harenna accessions, respectively. Hence, Harenna genotypes can be considered as parents in coffee improvement programs under limiting water conditions.
The study was carried out to determine the variations among different Coffea arabica germplasm lines in hydraulic resistances under controlled nursery settings at the Jimma Agricultural Research Center in southwest Ethiopia. The experimental treatments included contrasting shade conditions (moderate shading v. full sunlight) and seedlings of 12 arabica coffee accessions of varying geographical areas in Ethiopia. Root hydraulic conductance and hydraulic resistances in the whole-shoot and different shoot parts were measured using a high-pressure flow meter. The results depicted significantly lower hydraulic resistances in the whole-shoot and in various shoot segments from the full sunlight exposed seedlings. The contribution of root and shoot resistances varied significantly in response to shade treatments. Likewise, seedlings of coffee accessions exhibited significant variation in the resistance contribution of the main stem-cut to whole-shoot resistances. The maximum hydraulic resistances in main stem-cut were noted in the order of Bonga>Berhane-Kontir>Yayu>Harenna coffee populations, suggesting a direct relationship between growth and hydraulic characteristics. The resistance contributions declined across seedling growth parts: roots>leaf>whole-shoot>lateral branch>petiole, which is consistent with hydraulic gradients and thus sensitivity to drought stress. Moreover, the findings indicate the possibility of predicating the latter stage performances of coffee genotypes at specific field locations. In support of the hypothesis, the effects of both environmental and genetic factors need to be considered in fully understanding drought tolerance strategies in coffee genotypes. In view of the continuous multifaceted threats on the untapped coffee genetic resources, due mainly to, among others, anthropogenic activities coupled with climate change, there is an urgent need for global collaborative actions for future development of the coffee sector in Ethiopia and worldwide.