Natural resistance to Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera: Noctuidae) in traditional maize varieties cultivated in southeast Brazil

The aim of this research was to assess the natural resistance of traditional maize (Zea mays L.) varieties cultivated in Espírito Santo, Brazil, to Spodoptera frugiperda. Additionally, the study aimed to investigate the leaf structures, chemicals, biochemicals, and cellular factors associated with this resistance, with the ultimate goal of identifying promising varieties for genetic breeding. The evaluation included a total of 77 traditional maize varieties, along with four commercial varieties cultivated throughout Brazil. The experiment followed a randomized complete block design with three replications, and the plots consisted of three rows, each 3 m in length and spaced 1.0 m apart, with the central row representing the useful area of the plot. Traditional varieties exhibiting low herbivory by S. frugiperda underwent antixenosis tests for feeding and oviposition. Leaf samples were subjected to histology and microscopy tests. Out of the field tests, eight maize varieties displayed no evidence of S. frugiperda attacks, suggesting either natural resistance or antixenosis by the pest. Antixenosis analysis identified variety Cativerde 02 with minimal herbivory by S. frugiperda, comparable to the negative control, the transgenic hybrid Feroz Viptera 3 (Syngenta), known for its resistance to the pest. Histological and microscopy analyses revealed distinct chemical elements in the traditional Cativerde 02 compared to the controls, and the presence of silica crystals in this variety suggested a potential protective mechanism against herbivory.