Sorghum is a food staple for millions of people in sub-Saharan Africa, but parasitic weeds of the Striga genus greatly diminish its production. An efficient and cost-effective way of managing Striga in smallholder farms in Africa is to deploy resistant varieties. 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. We exploit a Striga resistance mechanism that hinges on essential communication molecules – strigolactones exuded by hosts to trigger parasite seed germination. We used the Sorghum Association Panel (SAP) to search for sorghum genotypes with a mutation on the LOW GERMINATION STIMULANT 1 ( LGS1) locus that makes them ineffective in inducing Striga germination. Our analysis led us to identify new 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 far-reaching implications for improving food security in Africa by potentially reducing crop losses due to Striga parasitism.

Fitness responses to environment can shape species distributions, though opposing eco-evolutionary processes can obscure environmental effects. For example, host specificity influences parasite dynamics, but is unclear how adaptation of parasites to local host communities may scale up to continental distributions. Here, we develop a macroecological framework to determine how host community structure affects the distribution of specialist and generalist populations of Striga hermonthica, an African parasitic plant of cereal crops. Combining data from global crop production and parasite experimental trials, we find that parasites perform best on the host species that is most common in their location of origin. Moreover, niche model contrasts predict parasite specialization on two hosts that evolved alongside Striga during domestication (pearl millet and sorghum), indicating that specialist parasites may be most likely to occur where host niches differ most in multivariate environmental space.  Our study demonstrates that patterns of parasite local adaptation to host communities can emerge at continental scales and that differential environmental tolerances of hosts indirectly shape the distribution of specialist and generalist parasites.  By predicting spatial dynamics of parasite specialization versus generalization directly from environmental data, our approach may help inform current and future management of pests and disease.