Review Article: Genetics and Breeding Overview for Coffee Wilt Disease Resistance

Abstract

The presence of intra-and inter specific variability in the coffee species provide a potential source of resistance to Coffee Wilt Disease (CWD). Additionally, the existence of Robusta and Arabica wilt pathogenic forms enables to design effective breeding strategies to develop resistant cultivars towards each population. The inheritance of resistance to Fussarium xylarioides in Coffea canephora suggested that resistance is controlled by polygenic. Heritability is low to moderate with low genetic gains of choosing a progeny of resistant parents as source of planting materials; so that resistant clones should be propagated vegetatively. Alternatively, in Arabica CWD resistance has been suggested that presence of certain quantitative with qualitative resistance. Moreover, Arabica coffee was lacking or low heterosis for resistance, predominance of additive over non additive genetic effects and estimated of high heritability coupled with genetic advance as percent of mean (GAM) for resistance and incubation period; indicated that selection and hybridization are important to improve population and to obtain segregating generation, respectively. The resistant Arabica coffee genotypes were also significantly associated with extended incubation period, leaf area, stem diameter and minimum number of defoliated leaves than the susceptible genotypes. For further screening, promising resistant Arabica coffee genotypes were planted and also under evaluation for other major diseases, yield and quality traits at sick plot of Gera agricultural Research Sub Center, Ethiopia. Generally, CWD symptoms, source of resistance, host-pathogen interaction, resistance screening techniques, genotypes evaluation, inheritance of resistance, hybridization and resistant variety development approaches were comprehensively discussed.