Cracking open the witch's spell book: the witchweed genome provides clues to plant parasitism

Abstract

Cracking open the witch's spell book: the witchweed genome provides clues to plant parasitism Striga hermonthica (purple witchweed; Fig. 1) is the most notorious parasitic weed in the world. It attacks staple food crops of maize, sorghum, millet and rice, primarily in sub-Saharan Africa, contributing to hunger in the region and directly impacting human lives with an immediacy that is not matched by most other parasitic weeds. Striga hermonthica lives up to the imagery evoked by its common name, casting a curse on the host crop, as well as the unfortunate farmers whose fields it infests. Despite decades of study and incremental progress in controlling this weed, witchweeds persist and have even expanded their ranges (Parker, 2012). Therefore, the paper by Qiu et al. (2022; pp. 622-638), in this issue of New Phytologist signals a potential turning point in Striga research. The paper presents a draft of the S. hermonthica genome that is a milestone in itself, providing insight into the makeup and evolution of this species. But it also takes the next step, leveraging the genome in combination with a population genetics analysis to identify several candidate genes for parasite virulence.

The first example of extreme and independent host plant shifts mediated by parasitic plants in insects

“…One feature of parasitic plants that could explain this pattern is the existence of similar chemical compounds between dodders and broomrapes (Rehker et al, 2012), like those involved in haustorium formation (e.g. Sun et al, 2018;Qiu et al, 2022;Westwood, 2022) that potentially facilitated the detection of these distant plants by one or a few Smicronychini lineages towards parasitic Orobanchaceae (although their detectability by Smicronychini have never been put to the test). Additionally, a second feature of parasitic plants is that they may share similar host plants and therefore show some degree of chemical similarity according to the proximity of their host plants.…”