Vieira, A., Diniz, I., Loureiro, A., Pereira, A.P., Silva, M.C., Várzea, V. & Batista, D. (2018) Aggressiveness profiling of the coffee pathogen Colletotrichum kahawae.Plant Pathology, 68(2), 358-368. DOI:10.1111/ppa.12950 (IF2017 2,303; Q1 Agronomy)
Colletotrichum kahawae is a specialized plant pathogen of Arabica coffee in Africa, able to infect green berries. The economic impact of this pathogen leads to the urgent need of better understanding its pathogenic lifestyle, namely 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. Our 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 the isolates’ profile, 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 improve coffee breeding programs, through the selection of tester isolates for pre‐screening of resistant coffee materials and offers the opportunity to engage on future genotype‐phenotype studies.