Heterosis and Combining Ability Analysis for Coffee Quality in Diallel Crosses of Diverse Coffee (Coffea arabica L.) Parents in Origin

Abstract

In view of the lack of study on heterosis and combining ability in coffee quality breeding programs of Ethiopia, the present study was conducted on six distinct Coffea arabica L. lines in origin and 12 hybrids made among them in half diallel fashion to evaluate coffee hybrids for Sidamo coffee quality, to estimate heterosis effects for different coffee quality  parameters and to determine the gene actions involved in controlling the quality parameters. Coffee samples were prepared during the 2002/2003 cropping season from hybrids and parents planted at the Wonago  Agricultural Research Sub-station (06o 03’ N and 38o 03’ E) in Sidamo  following a randomized complete block design. The coffee samples were evaluated for Sidamo coffee quality at the National Coffee and Tea  Liquoring and Inspection Center. The hybrids exhibited positive and  significant heterosis that ranged from 14 to 33% relative to the commercial Sidamo coffee variety for most of the parameters studied. Two hybrids;  7440 x 75227 and 744 x 1681, evaluated as having highly acceptable  Sidamo coffee quality were the best specific combinations and heterotic for all coffee quality parameters. Two Kaffa coffee parents namely, 7440 and 75227 were good combiners and produced hybrids better than the  commercial Sidamo coffee variety for Sidamo coffee quality. Predominance of non-additive gene actions were detected for acidity, body, cup quality and overall Sidamo coffee quality and additive gene action was important for the expression of flavor. The results of this study suggested selection of parents on the basis of their quality performance regardless of their origin and crossing among them is an appropriate breeding method to improve target region coffee quality. This study was conducted using coffee parents obtained only from two coffee growing regions and the results might not be sufficient to reach at a general conclusion for all coffee types in Ethiopia. However, the present findings can be used as good evidence for the possibility of using coffee lines of diverse origin and their crosses to improve unique coffee quality of the target region.

Keywords: Additive Gene Action; Coffea arabica; Combining Ability; Heterosis; Non-additive Gene Action; Sidamo Coffee Quality