Steven RUNO

Tuesday, 25 May 2021 | 12:00 noon – Cape Town, SOUTH AFRICA

Department of Biochemistry, Microbiology and Biotechnology Kenyatta University, KENYA

Genetic basis of Striga (witchweed) resistance in sorghum

(Host: L. Donaldson)

Striga (witchweed) is a major constrain of cereal production in sub Saharan Africa, predicted to cause 30-100 percent yield losses and USD 7billion annually. Current control strategies for the parasite are only moderately effective or out of reach for resource poor farmers in SSA. Host resistance is the most effective strategy but this is limited by availability of sources of resistant plant varieties. We have combined genome wide association studies (GWAS) and RNA sequencing to dissect the genetic basis of Striga resistance in sorghum. We have also determined the genetic basis of virulence in Striga. Our studies show that sorghum employs various Striga resistance mechanisms including: i) mechanical barriers that block parasite entry, ii) elicitation of a hypersensitive reaction that interfere with parasite development, iii) the inability of the parasite to develop vascular connections with hosts, iv) low germination stimulation of Striga germination. Resistance genes underpinning the resistance correspond with the resistance mechanisms and include pleiotropic drug resistance proteins that transport resistance molecules; xylanase inhibitors involved in cell wall fortification. On its part, Striga uses cell wall degrading enzymes, among other effectors to overcome host resistance. Additionally, these mechanisms are mediated by a well coordinated hormonal cross-talk. Our findings are of fundamental importance to developing durable and broad-spectrum resistance against Striga and have far-reaching applications in many SSA countries where Striga threatens the livelihoods of millions of smallholder farmers that rely on sorghum as a food staple.