Screening F1 arabica hybrids for resistance to coffee berry disease (Colletotrichum kahawae): insights from field and controlled conditions

Abstract

Coffee berry disease (CBD), caused by Colletotrichum kahawae, remains one of the most destructive diseases of Arabica coffee, leading to substantial yield losses during high infection seasons in major coffee-growing regions, including Tanzania. Developing resistant varieties is a sustainable strategy for managing CBD, and breeding programs increasingly rely on host resistance to mitigate its impact. This study evaluated the response of eight F1 hybrid genotypes of Arabica coffee—F90/64/4660 × KP423, F89/64/4660 × KP423, F45/64/2049 × KP423, F24/64/902 × KP423, F45/64/2061 × KP423, F24/64/886 × KP423, VC 298, and KP423—against three C. kahawae isolates (2006/14 from Kibosho–Kombo, 2019/16 from Ugano-Mbinga, and 2019/11 from Maua Kilema). Coffee berries were inoculated under both field conditions and controlled environments using a spore suspension spray method. In controlled assays, berries were maintained in humidity boxes at 24 ± 2°C, while field inoculations required humid conditions and an optimum temperature of 30°C. Disease severity was assessed using a modified 0–4 scale, and incidence was recorded as the percentage of infected berries. Inoculated berries developed typical CBD symptoms, including brown spots and sunken lesions. Results revealed that two genotypes (F90/64/4660 × KP423 and F89/64/4660 × KP423) exhibited complete resistance, showing no infection across all isolates and environments. Among the isolates, 2006/14 from Kibosho–Kombo was the most aggressive, producing higher infection rates. These findings highlight the potential of resistant genotypes for incorporation into breeding programs and demonstrate the value of aggressive isolates as screening tools for developing durable resistance to CBD in Tanzania.