Aggressiveness profiling of the coffee pathogen Colletotrichum kahawae

Abstract

Colletotrichum kahawae is a specialized plant pathogen of arabica coffee in Africa, able to infect green berries. The economic impact of this pathogen means there is an urgent need to better understand its pathogenic lifestyle, in particular its aggressiveness. In this study, several quantitative traits including disease severity, latent period and incubation period were measured to concomitantly assess the aggressiveness of 26 C. kahawae isolates. The results show that the area under disease progression curve is the most informative variable, particularly when joined together with the index disease intensity 10 days after inoculation and latency period, while the incubation period is not a reliable trait to distinguish aggressiveness levels in C. kahawae. This study also confirms the suitability of hypocotyls and detached green berries to perform C. kahawae aggressiveness assays, revealing that hypocotyls are a more reproducible testing material. Based on isolate profiles, three aggressiveness classes were established (high, moderate and low). A cytological analysis of representative isolates from each class showed that aggressiveness can be related to the development of post‐penetration stages, rather than conidia germination and appressoria differentiation. This study provides, for the first time, the best metrics to evaluate C. kahawae aggressiveness, characterizing the profile of a broad range of isolates, and defining a set of parameters that can be used to classify new isolates. Furthermore, the collected information will contribute to the improvement of coffee breeding programmes, through the selection of tester isolates for prescreening of resistant coffee materials, and offers the opportunity to engage on future genotype–phenotype studies.

Resistencia genética a la Enfermedad de la Cereza del Café en variedades cultivadas en Colombia.

“…Reportes de Van der Vossen y Waweru (1977) indican que en temperaturas superiores a 24°C los genotipos susceptibles mostraron infección reducida o nula, mientras que a temperaturas inferiores a 17°C genotipos de alta resistencia desarrollaron lesiones. Resultados similares son reportados por Vieira et al (2019) quienes hallaron alta reproducibilidad de la prueba sobre hipocótilos y frutos desprendidos en variedad Caturra (CIFC 19/1).…”

Evaluation of coffee berry disease resistance (Colletotrichum kahawae) in F2 populations derived from Arabica coffee varieties Rume Sudan and SL 28

“…Isolates of Colletotrichum kahawae were obtained from freshly infected coffee berries in the field and multiplied on malt extract agar (MEA) for a period of about 15 days in the laboratory. To stimulate conidia production, isolates were cultured on coffee leaf extract agar medium for 7 days under a photoperiod of 12 h at 22°C and then sub-cultured on 90-mm polystyrene petri dishes containing malt extract agar (40 g L -1 , MEA; Oxoid) for 7 days under the same photoperiod (Vieira et al, 2019). Inoculum was obtained by dislodging and harvesting the conidia by flooding the plate with 5 mL of sterile distilled water and the suspensions passed through four layers of sterile muslin cloth to remove mycelia (Vieira et al, 2019).…”

“…To stimulate conidia production, isolates were cultured on coffee leaf extract agar medium for 7 days under a photoperiod of 12 h at 22°C and then sub-cultured on 90-mm polystyrene petri dishes containing malt extract agar (40 g L -1 , MEA; Oxoid) for 7 days under the same photoperiod (Vieira et al, 2019). Inoculum was obtained by dislodging and harvesting the conidia by flooding the plate with 5 mL of sterile distilled water and the suspensions passed through four layers of sterile muslin cloth to remove mycelia (Vieira et al, 2019). Concentrations of spore suspensions were determined using a haemocytometer (NEUBAUER Scientific International, Germany).…”

“…Coffee (Coffea spp.) is among the most important commodities in the tropical countries of the world (Vieira et al, 2019). It is commercially grown in more than 10.5 million ha in 80 different countries worldwide (Van der Vossen et al, 2015).…”

“…Coffee berry disease caused by the fungal pathogen Colletotrichum kahawae, is a specialized hemibiotrophic pathogen of C. arabica L. (Vieira et al, 2019). Unlike other Arabica coffee diseases, CBD is still restricted to the African continent despite favourable climatic conditions in certain high-altitude Arabica coffee growing areas of Latin America and Asia (Agwanda et al, 1997;Van der Vossen et al, 2015).…”