Abstract:
Hararghe coffee improvement both for yield and quality is vital for the sustainability of its production and fetches premium prices in world market, but limited information on genetic variability and association of morpho-agronomic and bean quality traits of Hararghe coffee collections. This research was conducted to assess genetic variability and determine the associations among morpho-agronomic and bean quality traits in Hararghe coffee collections. Sixty-four collections evaluated for morpho-agronomic traits in simple lattice design at Mechara Agricultural Research Center in 2021/22, and bean quality traits of collections determined in complete randomized design with three replications at coffee quality laboratory of Jimma Agricultural Research Center. The analysis of variance revealed the presence of significant differences among coffee collections for 31 morpho-agronomic and bean quality traits. The collections had 0.6 to 2.02 t ha-1 bean yield and total coffee quality ranged between 76.33 to 86.33%. The yield of 11 collections was higher than the best yielding Mocha variety (1.63 t ha-1 ) and 20 collections had total coffee quality better than the variety that had highest total coffee quality among check varieties. The genotypic and phenotypic coefficient of variation for morpho-agronomic and bean quality traits ranged from 1.42% to 35.45% and 2.63% to 38.42%, respectively. The broad sense heritability and genetic advances as percent of mean ranged from 17.88% to 88.82% and 1.47% to 67.97%, respectively. Coffee yield had positive and significant genotypic and phenotypic correlation with plant height, stem diameter, number of primary branches and canopy diameter of which plant height and stem diameter had positive direct effects on yield at genotypic and phenotypic levels. Number of primary branches and canopy diameter had positive indirect effects on yield via plant height and hundred beans weight at genotypic level. Yield had positive and significant genotypic correlation with plant height up to first primary branch and total raw beans quality, but both had high negative direct effect on yield. Total coffee quality showed positive and significant genotypic and phenotypic associations with acidity, astringency, body, flavor, and overall standard coffee quality of which acidity, body, and flavor exerted positive direct effects on total coffee quality. Astringency and overall standard coffee quality exerted high positive indirect effects via acidity on total coffee quality at genotypic and phenotypic levels. Beans shape and make had also positive direct effect on total coffee quality at phenotypic level and the two traits also had positive and significant phenotypic correlation. The eight principal components (PCs) with eigenvalue >1 accounted 82.75% of the total variation of coffee collections. The first three PCs (PC1, 2 and 3) contributed 53.58% of the total variation while the remained five PCs explained 29.17% of the total variation. Euclidean distance of pair of collections ranged from 2.82 to 14.1 with average of 7.66. The genetic cluster analysis grouped collections into seven clusters with inter-cluster distance ranged from 5.08 to 10.43 identified from Euclidean distances matrix. The results showed the existence of variability among Hararghe coffee collections, 11 and 20 collections had higher yield and bean quality better than the best performing check varieties, respectively, which can be used for further evaluation to the development of new varieties.