Ecology and evolutionary dynamics of the A-strain maize streak virus and the decade-long strategies targeting streak-resistant maize.

The A-strain maize streak virus (MSV-A; genus Mastrevirus, family Geminiviridae) is a single-stranded DNA (ssDNA) virus that severely constrains the production of maize in sub-Saharan Africa and other places where its insect vectors thrive. In this review, we discuss the ecology- and genomics-driven evolution of this economically important virus and strategies targeting streak resistance in maize. Evolution of MSV-A is largely driven by the interplay of mutation, recombination and selective forces that may sustain fitness and result in host adaptation. In the last decade, research efforts, including fine-mapping of quantitative trait loci (QTL), gene pyramiding, clustered regularly interspaced short palindromic repeats (CRISPR) techniques, microRNA gene silencing and farming practices, have had key roles in creating maize genotypes that are resistant to streak diseases caused by MSV-A and other plant-infecting viruses. However, these techniques may also foster the rapid emergence of editing-resistant variants, requiring more thorough and rigorous validations for desired results. We propose a five-cardinal agenda for future research covering layered surveillance-supported host resistance, evolutionary surveillance, agro-ecological alignment of breeding, escape-aware editing stewardship and policy harmonisation. Moreover, the in-depth understanding of the interplay between pathogens, hosts, and biotic interventions for breeding resistance is central to achieving crop improvement, agricultural productivity, and food security.