Strigolactone biosynthesis lgs1 mutant alleles mined from the sorghum accession panel are a promising resource of resistance to witchweed (Striga) parasitism

Abstract

Societal Impact StatementStriga is a parasitic plant that greatly limits the production of Africa's most staple cereals, including sorghum. Infection occurs when the parasite germinates in response to biomolecules emitted into the soil from the host's roots. Some sorghum genotypes harbor a mutation that makes them ineffective in stimulating Striga seed germination. This resistance is of great importance because of its possible application in Striga management. Here, additional resistant sorghum genotypes with varying levels of Striga resistance are discussed in the context of their candidacy for integration in breeding programs and their possible role in alleviating food insecurity in sub‐Saharan Africa by reducing crop losses because of Striga infestation.Summary Sorghum is a food staple for millions of people in sub‐Saharan Africa, but its production is greatly diminished by Striga, a parasitic weed. An efficient and cost‐effective way of managing Striga in smallholder farms in Africa is to deploy resistant varieties of sorghum. Here, we leverage genomics and the vast genetic diversity of sorghum—evolutionarily adapted to cope with Striga parasitism in Africa—to identify new Striga‐resistant sorghum genotypes by exploiting a resistance mechanism hinged on communication molecules called strigolactones (SLs), exuded by hosts to trigger parasite seed germination. We achieved this by mining for mutant alleles of the LOW GERMINATION STIMULANT 1 (LGS1) that are ineffective in stimulating Striga germination from the sorghum accession panel (SAP). Our analysis identified lgs1 sorghum genotypes, which we named SAP‐lgs1. SAP‐lgs1 had the SL exudation profile of known lgs1 sorghum, whose hallmark is the production of the low inducer of germination, orobanchol. Laboratory and field resistance screens showed that the SAP‐lgs1 genotypes also exhibited remarkable resistance against Striga. Our findings have the potential to reduce crop losses because of Striga parasitism and therefore have far‐reaching implications for improving food security in Africa.