Susceptibility and Yield Response of Commercial Corn Hybrids to Maize Dwarf Mosaic Disease

Maize dwarf mosaic (MDM) is one of the most important virus diseases of maize worldwide. Caused by the potyviruses maize dwarf mosaic virus (MDMV) or sugarcane mosaic virus (SCMV), MDM can cause up to 90% yield loss in susceptible hybrids. One of the most effective management strategies for MDM is growing potyvirus-resistant corn varieties. However, yield impacts associated with MDM and the corresponding efficacy of genetic resistance present in modern United States commercial hybrid lines is uncharacterized. In this study, we evaluated the disease response of 78 commercial hybrids to MDMV and SCMV and quantified yield losses associated with infection over multiple trials. We determined that while 97% of the hybrids tested were resistant to MDMV, 100% were susceptible to SCMV, with mean disease incidence per line averaging between 45 and 78% across six trial years. Despite only one hybrid displaying visible mosaic symptoms when inoculated with MDMV, MDMV reduced average yields by approximately 5% across all hybrids compared with the mock-inoculated treatment. The yield impact of SCMV was more severe, reducing average yields by 10% across replicated experiments. These results indicate that while most commercial hybrids are resistant to MDMV, possibly due to the presence of the major Scmv1 resistance locus on chromosome 6, additional potyvirus resistance genes are needed to manage SCMV-induced MDM. Pyramiding resistance loci, such as Scmv2 on chromosome 3 or Scmv3 on chromosome 10 in addition to Scmv1, could be an effective strategy to mitigate the yield impact of MDM disease.