Development of DNA markers for assisted selection of cassava resistant to cassava mosaic disease (CMD).

Cassava is an important staple crop in tropical and subtropical regions. Cassava mosaic disease (CMD) is one of the most dangerous diseases affecting cassava production in Africa. Since the first reported in Southeast Asia in 2015, the CMD prevalence has become a concern in Southeast Asia. To combat it, CMD resistance has been introduced from African cassava into Asian elite cultivars. However, efficient DNA markers for the selection of CMD resistance are not available. The CMD2 locus confers resistance to African cassava mosaic virus via non-synonymous substitutions in the DNA polymerase δ subunit 1 gene (MePOLD1). Here, we developed DNA markers to identify the mutations providing the resistance. We examined the association between the resistance score in CMD-infected fields and the genotypes of hybrids of CMD-resistant and ‑susceptible Asian lines. Our study provides powerful tools to the global cassava breeding community for selecting CMD resistant cassava.