Physiological and ecological warnings that dodders pose an exigent threat to farmlands in Eastern Africa

Abstract

Invasive holoparasitic plants of the genus Cuscuta (dodder) threaten African ecosystems due to their rapid spread and attack on various host plant species. Most Cuscuta species cannot photosynthesize and hence rely on host plants for nourishment. After attachment through a peg-like organ called a haustorium, the parasites deprive hosts of water and nutrients, which negatively affects host growth and development. Despite their rapid spread in Africa, dodders have attracted limited research attention, although data on their taxonomy, host range, and epidemiology are critical for their management. Here, we combine taxonomy and phylogenetics to reveal the presence of field dodder (Cuscuta campestris) and Cuscuta kilimanjari (both either naturalized or endemic to East Africa), in addition to the introduction of the giant dodder (Cuscuta reflexa), a south Asian species, in continental Africa. These parasites have a wide host range, parasitizing species across 13 angiosperm orders. We evaluated the possibility of C. reflexa to expand this host range to tea (Camelia sinensis), coffee (Coffea arabica), and mango (Mangifera indica), crops of economic importance to Africa, for which haustorial formation and vascular-bundle connections in all three crops revealed successful parasitism. However, only mango mounted a successful post-attachment resistance response. Furthermore, species distribution models predicted high habitat suitability for Cuscuta spp. across major tea- and coffee-growing regions of Eastern Africa, suggesting an imminent risk to these crops. Our findings provide relevant insights into a poorly understood threat to biodiversity and economic wellbeing in Eastern Africa, and provide critical information to guide development of management strategies to avert Cuscuta spp. spread.

Host Resistance to Parasitic Plants—Current Knowledge and Future Perspectives

“…may be enormous and unpredictable. For example, C. reflexa is an emerging threat to tea, coffee, and mango production in Eastern Africa [ 16 ], C. campestris is a well-known pest on sugar beet in many European countries [ 17 ], and C. gronovii is damaging cranberry production in North America [ 18 ]. Yield losses may reach 50–70% of the expected [ 19 , 20 ], and the quality of the yield may be also negatively affected [ 21 ].…”

Rising from the shadows: Selective foraging in model shoot parasitic plants

“…Their intimate physiological connection with their often closely related host and, in some cases, resilient seed banks, make it challenging to manage infestations (Benvenuti et al, 2005; Parker, 2012; Vurro et al, 2017). Increased concerns in a context of global change foster the need of refining predictive models to guide conservation of endangered species and pest control (Cai et al, 2022; Masanga et al, 2021; Ren et al, 2020). While successful parasitism critically depends on efficient host location, evidence has accumulated that parasitic plants can evaluate the quality of available hosts and ‘choose’ which ones they parasitise (Li et al, 2023; Marquardt & Pennings, 2010; Sandner & Matthies, 2018).…”

“…Their intimate physiological connection with their often closely related host and, in some cases, resilient seed banks, make it challenging to manage infestations (Benvenuti et al, 2005;Parker, 2012;Vurro et al, 2017). Increased concerns in a context of global change foster the need of refining predictive models to guide conservation of endangered species and pest control (Cai et al, 2022;Masanga et al, 2021;Ren et al, 2020).…”

Integrated metabolomic and transcriptomic analyses of the parasitic plant Cuscuta japonica Choisy on host and non-host plants

“…Moreover, resistant hosts, including sweet potato and tomato, can produce degrading enzymes in cell walls and inhibit the penetration of haustorium into plant tissues [3]. Masanga et al [40] found that Mangifera indica successfully mounted a post-attachment resistance response to dodder. In summary, in direct contact with haustoria, epidermal tomato cells elongate and die following a hypersensitive response, whereas a secondarily modified tissue is formed in the hypodermis to protect against haustoria penetration [23].…”