Abundance of Dalbulus maidis and impact of maize rayado fino disease on different genotypes in field conditions in Santa Catarina, Brazil

Abstract

Corn stunt complex disease has been a major problem to maize production in Brazil. Dalbulus maidis incidence can vary greatly over the years, as well as the occurrence of corn stunt diseases. Among the corn stunt pathogens, the maize rayado fino virus (MRFV) is involved in this disease complex. MRFV is persistently transmitted by the corn leafhopper Dalbulus maidis (Hemiptera: Cicadellidae) in a persistent propagative relationship. In this work, we assessed the abundance of D. maidis and rayado fino in experimental field plots with a commercial hybrid (P4285 VYHR) and an open pollinated variety (SCS156 Colorado) in the early phase of the planting in the late-sowing season, in two consecutive crop years (2020–21 and 2021–22), in Chapecó, Santa Catarina (South Brazil). Also, we evaluated the incidence of rayado fino and counted corn leafhoppers that were infesting MRFV-symptomatic and asymptomatic plants. D. maidis did not sort between the two maize genotypes in field conditions, but preferentially infests asymptomatic plants. This could be an evidence for the vector manipulation to aid pathogen spread. Incidence of rayado fino is greater in P4285 than in Colorado in early vegetative stages of maize and impacted plant production in about 40%. Additionally, we evaluated the incidence of rayado fino in 18 commercial maize genotypes in a field plot experiment at 50 days after sowing in the early-sowing season of the 2022–23 crop year. These genotypes showed a differential incidence to the disease, which could be explored in breeding programs. Our results also support that the corn stunt complex pathosystem, with the rayado fino viral disease, is dynamic and unequal over the years.