On the hunt for the alternate host of <i>Hemileia vastatrix</i>

Abstract

Coffee leaf rust (CLR), caused by the fungal pathogen <i>Hemileia vastatrix</i>, has plagued coffee production worldwide for over 150 years. <i>Hemileia vastatrix</i> produces urediniospores, teliospores, and the sexual basidiospores. Infection of coffee by basidiospores of <i>H. vastatrix</i> has never been reported and thus far, no alternate host, capable of supporting an aecial stage in the disease cycle, has been found. Due to this, some argue that an alternate host of <i>H. vastatrix</i> does not exist. Yet, to date, the plant pathology community has been puzzled by the ability of <i>H. vastatrix</i> to overcome resistance in coffee cultivars despite the apparent lack of sexual reproduction and an aecidial stage. The purpose of this study was to introduce a new method to search for the alternate host(s) of <i>H. vastatrix</i>. To do this, we present the novel hypothetical alternate host ranking (HAHR) method and an automated text mining (ATM) procedure, utilizing comprehensive biogeographical botanical data from the designated sites of interests (Ethiopia, Kenya and Sri Lanka) and plant pathology insights. With the HAHR/ATM methods, we produced prioritized lists of potential alternate hosts plant of coffee leaf rust. This is a first attempt to seek out an alternate plant host of a pathogenic fungus in this manner. The HAHR method showed the highest-ranking probable alternate host as <i>Psychotria mahonii</i>, <i>Rubus apetalus</i>, and <i>Rhamnus prinoides</i>. The cross-referenced results by the two methods suggest that plant genera of interest are Croton, Euphorbia, and Rubus. The HAHR and ATM methods may also be applied to other plant-rust interactions that include an unknown alternate host or any other biological system, which rely on data mining of published data.