20 January 2020
Staving off Striga, the ‘violet vampire’
Published online 28 March 2019
Scientists are getting closer to finding viable solutions to the menace of parasitic plants.
Among the threats to food security in sub-Saharan Africa is Striga hermonthica, or purple witchweed, called the ‘violet vampire’ because it wreaks havoc on fields of maize, millet, sorghum and rice.
The parasitic plant thrives on tapping into the roots of host plants and depriving them of nutrients and water. Crop yield losses caused by Striga are estimated to exceed US$10 billion every year. Control options exist, such as herbicides and mechanical removal, but they are costly and do not address the problem of the huge reserve of Striga seeds buried in the soil.
A technique called suicidal germination, which involves tricking Striga into germinating without a host plant and letting the germinated seeds die off, could offer a solution, but the strategy has not yet been fully explored under real-world conditions.
Now, researchers from Saudi Arabia, Burkina Faso, Japan, and the Netherlands have demonstrated1 that suicidal germination can be effective in natural rain-fed areas prone to Striga infestations. Describing their findings in the journal Plants, People, Planet, they say their method provides “a new means of sustainable cleaning of heavily Striga-infested pearl millet and sorghum fields in West Africa”.
Their study involved harnessing the power of plant hormones called strigolactones, which are known to trigger germination. Many scientists have been developing strigolactone analogs (compounds that mimic natural plant hormones) designed specifically to combat Striga.
The team compared three types of these compounds called MP1, MP3 and Nijmegen-1 and observed their effects under laboratory, greenhouse and field conditions. One remarkable finding was that Nijmegen-1 reduced Striga emergence in pearl millet fields by 65 per cent.
“The minimal demands of our protocol, in terms of water consumption and amount of selected strigolactone analogs, make it affordable and applicable at a large scale,” the authors say.
Pearl millet had not been studied adequately, explains co-author Salim Al-Babili, of King Abdullah University of Science and Technology (KAUST), “despite it being the staple food crop for millions of resource-poor subsistence farmers in sub-Saharan Africa.” If it can escape from Striga’s stranglehold, the cereal could contribute more effectively to food and nutritional security in the region.
“We will validate our results and conduct further studies with Nijmegen-1 and other suitable analogs,” he says.
Striga expert Yukihiro Sugimoto of Kobe University, Japan, who was one of the first to establish the feasibility of suicidal germination in 2016, says the current study “shows promise, as the practicality of the suicidal germination approach for controlling root parasitic weeds has been demonstrated in previous works2, 3 .”
Sugimoto cautions that, “cost-effectiveness and most importantly the biosafety of synthetic compounds must be confirmed before application to agricultural land.”
- Kountche, B.A. et al. Suicidal germination as a control strategy for Striga hermonthica (Benth.) in smallholder farms of sub‐Saharan Africa. Plants, People, Planet http://dx.doi.org/10.1002/ppp3.32 (2019).
- Zwanenburg, B. et al. Suicidal germination for parasitic weed control. Pest Manag. Sci. 72, 2016–2025 (2016).
- Samejima, H. et al. Practicality of the suicidal germination approach for controlling Striga hermonthica. Pest Manag. Sci. 72, 2035–2042 (2016).