title: Novel Sources of Witchweed (Striga) Resistance from Wild Sorghum Accessions.
abstract: Sorghum is a major food staple in sub-Saharan Africa (SSA), but its production is constrained by the parasitic plantStrigathat attaches to the roots of many cereals crops and causes severe stunting and loss of yield. Away from cultivated farmland, wild sorghum accessions grow as weedy plants and have shown remarkable immunity toStriga. We sought to determine the extent of the resistance toStrigain wild sorghum plants. Our screening strategy involved controlled laboratory assays of rhizotrons, where we artificially infected sorghum withStriga, as well as field experiments at three sites, where we grew sorghum with a naturalStrigainfestation. We tested the resistance response of seven accessions of wild sorghum of the aethiopicum, drummondii, and arundinaceum races against N13, which is a cultivatedStrigaresistant landrace. The susceptible control was farmer-preferred variety, Ochuti. From the laboratory experiments, we found three wild sorghum accessions (WSA-1, WSE-1, and WSA-2) that had significantly higher resistance than N13. These accessions had the lowestStrigabiomass and the fewest and smallestStrigaattached to them. Further microscopic and histological analysis of attachedStrigahaustorium showed that wild sorghum accessions hindered the ingression ofStrigahaustorium into the host endodermis. In one of the resistant accessions (WSE-1), host and parasite interaction led to the accumulation of large amounts of secondary metabolites that formed a dark coloration at the interphase. Field experiments confirmed the laboratory screening experiments in that these same accessions were found to have resistance againstStriga. In the field, wild sorghum had low Area under theStrigaNumber Progressive curve (AUSNPC), which measures emergence ofStrigafrom a host over time. We concluded that wild sorghum accessions are an important reservoir forStrigaresistance that could be used to expand the genetic basis of cultivated sorghum for resistance to the parasite.
authors.affiliation: Department of Biochemistry and Biotechnology, Kenyatta University Nairobi, Kenya.
authors.forename: Dorothy A
authors.initials: DA
authors.lastname: Mbuvi
authors.affiliation: Tropical Institute of Development InnovationsKampala, Uganda; Sudan Academy of SciencesKhartoum, Sudan.
authors.forename: Clet W
authors.initials: CW
authors.lastname: Masiga
authors.affiliation: Department of Biochemistry and Biotechnology, Kenyatta University Nairobi, Kenya.
authors.forename: Eric
authors.initials: E
authors.lastname: Kuria
authors.affiliation: Department of Biochemistry and Biotechnology, Kenyatta University Nairobi, Kenya.
authors.forename: Joel
authors.initials: J
authors.lastname: Masanga
authors.affiliation: Department of Biochemistry and Biotechnology, Kenyatta University Nairobi, Kenya.
authors.forename: Mark
authors.initials: M
authors.lastname: Wamalwa
authors.affiliation: Agricultural Research Cooperation Wad-Medani, Sudan.
authors.forename: Abdallah
authors.initials: A
authors.lastname: Mohamed
authors.affiliation: International Crops Research Institute for the Semi-Arid Tropics Nairobi, Kenya.
authors.forename: Damaris A
authors.initials: DA
authors.lastname: Odeny
authors.affiliation: Sudan Academy of SciencesKhartoum, Sudan; Commission for Biotechnology and Genetic Engineering, National Centre for ResearchKhartoum, Sudan.
authors.forename: Nada
authors.initials: N
authors.lastname: Hamza
authors.affiliation: Department of Biology, University of Virginia Charlottesville, VA, USA.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Timko
authors.affiliation: Department of Biochemistry and Biotechnology, Kenyatta University Nairobi, Kenya.
authors.forename: Steven
authors.initials: S
authors.lastname: Runo
keywords: Striga hermonthica benth.; Striga resistance; Sub-Saharan Africa; sorghum; sorghum bicolor; wild sorghum relatives; witchweed