Combining ability, heterosis and heritability studies can provide valuable information for designing appropriate breeding programs for resistance to coffee wilt disease (CWD), which caused by Gibberella xylarioides. The objective of this study was conducted to determine heterosis, combining ability, and heritability for resistance to CWD using an eight-parent half diallel cross (eight parents and 28 F1 hybrids). A susceptible control was used as a reference. All entities were artificially inoculated by the pathogen, and evaluated for CWD in the greenhouse at Jimma Agricultural Research Center (JARC), Ethiopia in 2015/16. The reactions of inoculated genotypes were measured as a percent of wilted seedling, incubation period, and number of yellow and defoliated leaves. Combined analysis of variance showed significant difference among genotypes for the characters measured. Better-parent heterosis (BPH) and mid-parent heterosis (MPH) for percent of wilted seedlings and the number of defoliated leaves showed negligible heterosis in desirable direction. However, considerable MPH was noticed for
longer incubation period. Both additive and non-additive gene actions were involved in controlling the inheritance of CWD resistance and incubation period; the additive gene effects being predominant. Parents P2 (971), P7 (974), P8 (370), and P5 (79233) showed highly significant negative general combining ability (gca) effects and found to be good general combiners for resistance to CWD. Moreover, specific combining ability (sca) effects of hybrids P7 x P8 (974 x 370) and P4 x P8 (8136 x 370) revealed that they are good combinations for resistance (low mean wilted seedlings percentage) and incubation period. Percent wilted seedlings showed high broad (88.27%) and narrow (75.41%) sense heritability coupled with 68.61% genetic advance. Generally, both pure line selection and pedigree selection after hybridization could be an effective resistance breeding approach for CWD management in Arabica coffee.
