Phenotypic stratification of corn stunt tolerance in a tropical public maize panel reveals contrasting extreme phenotypes

Abstract

Corn stunt is one of the most important diseases affecting maize (Zea mays L.) production in tropical regions of the Americas and is caused by a complex of pathogens transmitted by the corn leafhopper (Dalbulus maidis). The quantitative nature of tolerance to this disease, combined with strong environmental effects and heterogeneous infection pressure under field conditions, poses major challenges for the identification and selection of superior genotypes. The objective of this study was to perform phenotypic stratification of corn stunt tolerance in a tropical public maize panel in order to identify extreme phenotypes and support future genomic analyses. A total of 360 inbred lines were evaluated under natural infection using three complementary traits: sanity score in survivor plants, proportion of survivor plants, and whole sanity score. Substantial phenotypic variation was observed among lines, with continuous trait distributions, confirming the quantitative inheritance of corn stunt tolerance. Phenotypic stratification allowed the identification of highly tolerant and highly susceptible genotypes, indicating the presence of favorable allelic combinations within the evaluated germplasm. The proposed approach proved effective for characterizing genotype responses to corn stunt and provides a robust phenotypic foundation for extreme phenotype–based genome-wide association studies, in addition to contributing to the identification of potential parental lines to be used in breeding programs, contributing to maize breeding efforts aimed at improving tolerance to insect-vectored diseases in tropical environments.