Detection of mollicutes in maize plants and its insect vector, <i>Dalbulus maidis</i> , in Paraguay

Corn diseases caused by mollicutes have been present in Paraguay since 1990, but recent epidemics have brought attention to farmers and scientists. Local information about mollicutes incidence in maize is scarce and molecular confirmation of causal agents is unavailable in the literature. In 2023, a high incidence of typical mollicutes symptoms was found in hybrid maize plants from a field experiment in San Lorenzo, Paraguay. This study identified mollicute species in maize using molecular methods and evaluate their incidence, predominance and presence in the insect vector Dalbulus maidis. Molecular diagnostics identified Spiroplasma kunkelii and Maize bushy stunt phytoplasma (MBSP) in 87.1 and 71.4% of analysed samples, respectively, using primers targeting the spiralin and 16SrRNA genes. The infection rates of S. kunkelii and MBSP in D. maidis specimens collected in the same area were 22.2% and 16.6%, respectively. The incidence of symptoms in maize hybrids ranged between 21.1% and 52.8%. A negative correlation was observed between mollicutes incidence and grain production, resulting in a significant impact on yields. To our knowledge, this is the first molecular detection of S. kunkelii and MBSP in maize plants in Paraguay. Further research is necessary to evaluate management strategies for reducing mollicutes incidence.