New genetic opportunities from legume intercrops for controlling Striga spp. parasitic weeds

Abstract

In smallholder farming in East Africa, intercropping of maize with the cattle forage legume, Desmodium uncinatum Jacq., prevents parasitism by Striga hermonthica (Del.) Benth. (witchweed) through an allelopathic mechanism. Isoschaftoside, a di-C-glycosylflavone, isolated from the root extract and root exudate of Desmodium, interferes with in vitro radicle development of germinated Striga. The biosynthetic pathway of this class of compound is already mostly present in edible legumes and in cereals, so characterisation of the enzyme and genes that control C-glycosylflavone biosynthesis has the potential to create this protection mechanism in other agriculturally important plants.

Plant: soil interactions in temperate multi-cropping production systems

“…These techniques however require a change in system and the complex interactions make the outcome difficult to predict. Hence, most research has focused on extracting and synthesising the active weed inhibiting compounds to produce natural herbicides, which then can be applied onto fields (Fujii 2001;Singh et al 2003;Hooper et al 2009). …”

“…Common crops, such as durum wheat, oat, sorghum and fenugreek (Trigonella foenum-graecum) can be intercropped successfully to inhibit broomrape (Orobanche) and witches weed (Striga) species in grain and forage legumes without compromising the growth of the component crop (Lins et al 2006;Fernández-Aparicio et al 2008;Hooper et al 2009;Fernández-Aparicio et al 2010;Fernández-Aparicio and Rubiales 2012). The component crops can inhibit broomrape germination and/or trigger seed germination of said parasitic weeds leading to 'suicidal' germination.…”

Allelopathy as protectant, defence and growth stimulants in legume cereal mixed culture systems

“…Most farmers in Africa intercrop maize, sorghum and millet with legumes to increase crop production and achieve greater marginal revenue. These intercrops have been reported to reduce the infection by S. hermonthica due to underground interaction (Carson 1989;Carsky et al 1994;Oswald et al 2002;Hooper et al 2009). Similarly, growing sorghum in a mixture with cowpea, green gram and crotalaria (Crotalaria ochroleuca G. Don), as well as maize with crotalaria, significantly reduced Striga populations (Khan et al 2007).…”

“…One such weed, Striga, is parasitic on both monocots and dicots (Press & Graves 1995;Hooper et al 2009). Studies have shown that there are between 28 and 50 species of Striga, which belongs to the family Scrophulariaceae (Butler 1995;Press & Graves 1995;Bouwmeester et al 2003).…”

Farmers’ Perception and Constraints to the Adoption of Weed Control Options: the Case of Striga asiatica in Malawi

“…Various Striga control options such as use of resistant crop varieties, cereal-legume intercropping, trap crops that stimulate suicidal germination and nitrogen fertilizer application have been suggested (Frankie et al, 2006;Hooper et al, 2009). A combination of a wide range of technologies into an integrated Striga control (ISC) program has been identified as a feasible approach to contain the parasite.…”