Abstract:
Increasing coffee productivity is one of the highest national priorities of the rural development policy of
Ethiopia; and thus, the choice of promising genotypes from diverse genetic base and subsequent utilization of
hybrids is one of strategies of improving productivity. A half diallel analysis involving five parents, ten F1
hybrids of Coffea arabica and one check hybrid was studied for several quantitative traits to generate
information on combining ability. The genotypes were evaluated in a randomized complete block design
(RCBD) with three replications at Melko, Metu and Tepi research centers. Both General Combining Ability (GCA)
and Specific Combining Ability (SCA) mean squares were highly significant for yield indicating both additive
and non-additive gene actions are important for the inheritance of this economic trait; percentage relative
contribution of SCA over GCA was high indicates the predominance of non-additive gene action. Both the
additive and non-additive gene actions were involved in the control of the characters studied for fruit length,
fruit width, fruit thickness, bean length, bean width, bean thickness and 100-bean weight similar to
aforementioned trait. Parental line P4 found to be the best combiner for stem girth, length of first primary
branch and internode length showing significant and positive GCA effects for these traits; this parent may
contribute favorably for additive genes to its progenies for the synthesis of vigorous hybrids. Parental lines P4
and P5 were found good general combiners for yield showing highly significant GCA effects in across locations
GCA effects. These parental lines may have good prospect for the inclusion in the breeding program for yield
improvement in synthesis of new high yielding hybrid varieties. Nearly 90% of the crosses showed positive
SCA effects for yield out of which five crosses: P3XP5, P1XP5, P2XP5, P2XP4 and P3XP4 showed positive and
significant SCA values for yield indicating that these crosses were good combinations.
