Novel Sources of Witchweed (Striga) Resistance from Wild Sorghum Accessions
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Date
2017
Journal Title
Journal ISSN
Volume Title
Publisher
Frontiers in Plant Science
Abstract
Sorghum is a major food staple in sub-Saharan Africa (SSA), but its production is
constrained by the parasitic plant Striga that 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 to
Striga. We sought to determine the extent of the resistance to Striga in wild sorghum
plants. Our screening strategy involved controlled laboratory assays of rhizotrons, where
we artificially infected sorghum with Striga, as well as field experiments at three sites,
where we grew sorghum with a natural Striga infestation. We tested the resistance
response of seven accessions of wild sorghum of the aethiopicum, drummondii, and
arundinaceum races against N13, which is a cultivated Striga resistant 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 lowest Striga
biomass and the fewest and smallest Striga attached to them. Further microscopic and
histological analysis of attached Striga haustorium showed that wild sorghum accessions
hindered the ingression of Striga haustorium 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 against Striga. In the field, wild sorghum
had low Area under the Striga Number Progressive curve (AUSNPC), which measures
emergence of Striga from a host over time. We concluded that wild sorghum accessions
are an important reservoir for Striga resistance that could be used to expand the genetic
basis of cultivated sorghum for resistance to the parasite.
Description
Keywords
Striga resistance, Witchweed, Sorghum, Wild sorghum relatives, Sub-Saharan Africa Nomenclature, Striga hermonthicabenth, Witchweed, Sorghumbicolor
Citation
Mbuvi DA,MasigaCW,KuriaE, Masanga J,WamalwaM, MohamedA,OdenyDA,HamzaN, TimkoMPandRunoS(2017)Novel Sources ofWitchweed(Striga) Resistance fromWildSorghum Accessions. Front.PlantSci.8:116. doi: 10.3389/fpls.2017.00116