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Open Access Methodology

Striga parasitizes transgenic hairy roots of Zea mays and provides a tool for studying plant-plant interactions

Steven Runo1*, Sarah Macharia1, Amos Alakonya1, Jesse Machuka1, Neelima Sinha2 and Julie Scholes3

Author Affiliations

1 Biochemistry and Biotechnology Department, Kenyatta University, P. O. Box 43844, 00100 GPO, Nairobi, Kenya

2 Division of Plant Biology, University of California Davis, Davis, 1 Shields Avenue LSA 2231, 95616, Davis, CA, USA

3 Department of Animal and Plant Sciences, University of Sheffield, Sheffield, S10 2TN, United Kingdom

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Plant Methods 2012, 8:20  doi:10.1186/1746-4811-8-20

Published: 21 June 2012

Abstract

Background

Striga 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.

Results

We 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.

Conclusions

This rapid, high throughput, transformation technique will advance our understanding of gene function in parasitic plant-host interactions.

Keywords:
Maize; Striga hermonthica; Agrobacterium rhizogenes; Hairy roots; Composite plants