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. Keywords: Coffee Wilt Disease, Coffea Arabica , Coffea canephora , Resistance DOI: 10.7176/JEES/11-9-01 Publication date: September 30 th 2021
Highlights
Coffee wilt disease is a fungal vascular disease caused by Fusarium xylarioides or the sexual reproductive stage, Gibberella xylarioides (Steyaert, 1948; Heim and Saccas, 1950; Kranz and Mogk, 1973)
Evaluation of coffee genotypes for Coffee Wilt Disease (CWD) resistance At different time of artificial inoculation and screening programs, thousands of Arabica coffee genotypes are examined at seedling stage by different investigators in Ethiopia
Twelve Arabica coffee genotypes were tested from diverse agro ecological zones with different resistance reactions based on artificial inoculation test or natural CWD infested soils in order to verify previous results and select promising resistant genotypes (Figure 5)
Summary
Coffee wilt disease (tracheomycosis) is a fungal vascular disease caused by Fusarium xylarioides or the sexual reproductive stage, Gibberella xylarioides (Steyaert, 1948; Heim and Saccas, 1950; Kranz and Mogk, 1973). Its symptoms progress from inward curling and wilting of leaves to die back and death of affected trees. The pathogen invades the coffee tree and colonizes the xylem system. The production of coffee is today severely affected by this fungal disease (Silva et al, 2006; Serani et al, 2007). The disease is responsible for a reduction in the production of coffee beans and is accompanied by severe damage and death of millions of coffee bushes (Girma et al, 2001). CWD leads to about 37% reduction of coffee production (yield) at the farm level (from 1482 to 932 kg per sample farm); this led to a decline of income by 67% and the annual national crop losses attributed about 3360 tons. It varied from place to place in the range of 0 to 100% for incidence and 0 to 25% for severity (CABI, 2003)
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