Morphological and organoleptic charachterization of some coffee (Coffea arabica L.) Germplasm accessesions from gomma wereda, southwest Ethiopia

Abstract

Information on genetic variability for morphological andorganoleptic traits is a prerequisite for further improvement of the yield and quality of coffee . However, lack of information on genetic variability for speciality coffee accessions has been one of the major problems in coffee improvement program. Forty nine coffee (Coffeaarabica L.) germplam accessions ,which were collected from Gomma Wereda,were evaluated at Agaro with the objectives of assessing genetic variability and character associations for morphological and organoleptic traits. Data on 26 quantitative,13 qualitative and eight organoleptic characters were recorded.Morphological characterization was conducted in simple lattice design with two replications during 2011/12 cropping season.The analysis of variance showed significant (P<0.05) variation among the accessions for all morphological traits except percentage bearing primary branches, leaf area, bean thickness and rust incidence and the wide range of the mean values for most of the characters indicated the existence of variability among the tested materials.Estimates of variabilityindicated that high phenotypic (PCV) and genotypic coefficients of variation (GCV) were recorded for CBD severity and yield per tree. High heritability coupled with high genetic advance as percent of mean was observed for hundred bean weight and height up to first primary branch.Cluster analysis of quantitative characters groupedthe 49 coffee germplasm accessions into five clusters.This makes the germplasm accessions to be moderately divergent.The distances between most of these clusters were highly significantat (P< 0.01), suggesting the possibility of getting suitable accessions for hybridization program among the tested materials.PCA analysis showed the variation in the first two principal components, which explained the lion’s share of the observed variation, (42%), was mainly due to inter node length of main stem and primary branches, leaf length, hundred bean weight, plant height, number of main stem nodes, number of primary branches, length of primary branches, number of secondary branches and canopy diameter. Coffee yield showed positive and significant correlations with average inter node length of main stem,stem diameter, angle of primary branches andfruit length, width and thickness. Path coefficient analysis revealed that average inter node length of stem, stem diameter, angle of primary branches, fruit length and thickness, having significant and positive correlation, exerted positive direct effects on coffee yield. So, these traits can be used as indirect selection criteria to improve coffee yield per tree.With regards to organoleptic traits, all traits showed significantvariationamong the accessionsat (P<0.05).High phenotypic and genotypic coefficients of variation was observed for bitterness and astringency.Organoleptic traits such as flavor, overall standard, acidity and aromatic quality had high heritability. Bitterness and astringency showedmoderate heritability coupled with high genetic advance.Similarly, flavor had high heritability and moderate genetic advance as percent of mean. Hence, bitterness, astringency and flavor can be improved through selection.Cluster analysis based on organoleptic traits grouped the accessions into three groups which make them also moderately divergent. The principal component analysis showed the variation in first principal component, 63.7%, had been attributed to overall standard, flavor, acidity and aromatic quality.Correlation analysis revealed flavor and overall standard exhibited positive and significant genotypic correlation among each other and with aromatic quality, acidy and body.Pathanalysis showed that flavor exerted maximum direct effect and had positive and significant correlation with overall standard. Thus, flavor can be used as indirect selection criteria to improve the overall standard of coffee quality.Generally,the present study indicated the presence of variability for several morphological and organoleptic traits among the accessions.Therefore, the variability observed for yield, disease resistance and quality should be exploited in order to improve the yield and the quality of Gomma Wereda coffee. However,since high morphological variation between accessions is not a guarantee for a high genetic variation, molecular and biochemical studies need to be considered as complementary to morphological and organoleptic studies