Abstract
Coffee is one of the most consumed beverages in the world. It is also one of the most globally traded commodities. Coffee leaf rust (CLR), caused by the biotrophic fungus Hemileia vastatrix, is the most important disease affecting Arabica coffee growing worldwide, leading to significant yield losses if no control measures are applied. A deep understanding of the complex mechanisms involved in coffee-H. vastatrix interactions, such as the pathogen variability and the mechanisms governing plant resistance and susceptibility, is required to breed efficiently for durable resistance and design new approaches for crop protection. Here we summarize our current understanding across multiple areas related to pathogen infection, variability and candidate effectors, breeding for disease resistance, and the various components of the coffee immune system, by reviewing a comprehensive body of research on CLR and the advances recently made. We also update information about the defense responses activated by the application of plant resistance inducers, a promising alternative to fungicides in the control of CLR. Moreover, we identify and discuss future directions for further research.
Highlights
Coffee is a vital presence in the daily life of a significant share of the world’s population, with consumption of over 3 billion cups of coffee a day, it is the most valuable primary product in world trade, crucial to the economy of more than 50 countries, and constitutes the main source of livelihood for up to 25 million farmers and their families [1]
As promising as these strategies are for durable broad-spectrum resistance, they require the tagging of resistance genes by tightly linked markers, and their molecular characterization, which can be a hard task when dealing with highly complex polygenic traits in polyploid species
This review summarizes the progress made to date in the research of coffee-H. vastatrix interactions from both the plant and pathogen viewpoints
Summary
Coffee is a vital presence in the daily life of a significant share of the world’s population, with consumption of over 3 billion cups of coffee a day, it is the most valuable primary product in world trade, crucial to the economy of more than 50 countries, and constitutes the main source of livelihood for up to 25 million farmers and their families [1]. Plants are not able to defend themselves anymore and fall into the state of Effector-Triggered Susceptibility (ETS) [26,32] Once activated, both PTI and ETI induce a downstream of similar defenses, such as rapid accumulation of reactive oxygen species (ROS), changes in cellular ion fluxes, activation of protein kinase cascades, production of stress-related hormones, cell wall modifications and changes in protein and gene expression [26,28,34]. HR is considered to be one of the most important factors in the restriction of the pathogen growth, of obligate biotrophs [36,37] such as rust fungi, being responsible for race-specific resistance [38] Despite their differences and particular features, the two-layered defenses (PTI and ETI) should be considered as a continuum resulting in the activation of an overlapping set of immune reactions [39]. We discuss the main challenges for future research in this complex biological system
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