Abstract
BackgroundStriga species are noxious root hemi-parasitic weeds that debilitate cereal production in sub-Saharan Africa (SSA). Control options for Striga are limited and developing Striga resistant crop germplasm is regarded as the best and most sustainable control measure. Efforts to improve germplasm for Striga resistance by a non-Genetic Modification (GM) approach, for example by exploiting natural resistance, or by a GM approach are constrained by limited information on the biological processes underpinning host-parasite associations. Additionaly, a GM approach is stymied by lack of availability of candidate resistance genes for introduction into hosts and robust transformation methods to validate gene functions. Indeed, a majority of Striga hosts, the world’s most cultivated cereals, are recalcitrant to genetic transformation. In maize, the existing protocols for transformation and regeneration are tedious, lengthy, and highly genotype-specific with low efficiency of transformation.ResultsWe used Agrobacterium rhizogenes strain K599 carrying a reporter gene construct, Green Fluorescent Protein (GFP), to generate transgenic composite maize plants that were challenged with the parasitic plant Striga hermonthica. Eighty five percent of maize plants produced transgenic hairy roots expressing GFP. Consistent with most hairy roots produced in other species, transformed maize roots exhibited a hairy root phenotype, the hallmark of A. rhizogenes mediated transformation. Transgenic hairy roots resulting from A. rhizogenes transformation were readily infected by S. hermonthica. There were no significant differences in the number and size of S. hermonthica individuals recovered from either transgenic or wild type roots.ConclusionsThis rapid, high throughput, transformation technique will advance our understanding of gene function in parasitic plant-host interactions.
Highlights
Striga species are noxious root hemi-parasitic weeds that debilitate cereal production in sub-Saharan Africa (SSA)
Agrobacterium rhizogenes induces hairy roots in maize producing composite plants Agrobacterium rhizogenes composite plants are generally produced from wounding plant tissue e.g. leaves, cotyledons, or root hypocotyls, followed by inoculation with a culture of bacteria under in vitro or in vivo conditions
In summary maize composite plants were produced as follows: 5 day old maize seedlings were infected with A. rhizogenes K599 harbouring a Green Fluorescent Protein (GFP) reporter construct by an excision that split the main root in two halves approximately 4 mm from the tip
Summary
Striga species are noxious root hemi-parasitic weeds that debilitate cereal production in sub-Saharan Africa (SSA). Efforts to improve germplasm for Striga resistance by a non-Genetic Modification (GM) approach, for example by exploiting natural resistance, or by a GM approach are constrained by limited information on the biological processes underpinning host-parasite associations. Are the most important cereal weeds, The Striga life cycle is highly synchronized with that of the host and generally involves the stages of germination, attachment to host, haustorial formation, penetration, establishment of vascular connections, accumulation of nutrients, flowering and seed production [2]. Germination of Striga seeds only take place in response to chemical cues, most commonly strigolactones, produced by the host and in some cases non host species [3,4]. After penetration of the cortex, haustorial cells undergo a remarkable differentiation process to form vessels that form a continuous bridge with the host xylem [5] that serve as a conduit for host derived nutrients and water
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