Antixenosis in cotton genotypes (Gossypium hirsutum var. marie galante) to Spodoptera frugiperda (Lepidoptera: Noctuidae) mediated by trichome and gossypol densities

Abstract

Cotton (Gossypium hirsutum L.) is one of the most important crops in Brazil and pest incidence limits its yields. The fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), native to tropical and subtropical America, spread and rapidly became an invasive pest worldwide. It is a polyphagous pest that feeds on up to 353 plant species including cotton. The objective of this study was to evaluate the antixenosis to S. frugiperda in 27 cotton genotypes, comparing varieties with non- commercial genotypes. The attractiveness was estimated in no-choice and free-choice tests, offering leaf discs of the 27 cotton genotypes to S. frugiperda, and counting the number of caterpillars feeding at 3, 5, 10, 15, and 30 minutes and 1, 2, 6, 12, and 24 hours after their release. The numbers of trichomes and gossypol glands per cm2 were measured on abaxial and adaxial surface. The free-choice test was performed in a randomized block design with the 27 genotypes (treatments) and 20 arenas (replicates). The no-choice assay was conducted as a completely randomized design with 18 genotypes and 20 replicates. The non-commercial genotypes PI0440, CE0467, PI0416, BA0512 and MA0425 presented antixenosis against S. frugiperda. In the free-choice test the cultivar BRS Buriti and the genotype PI0429 were the most attractive to S. frugiperda, while in no-choice test, the genotype PI0429 was the most attractive. High trichome density and gossypol glands did not influence the attractiveness of S. frugiperda in cotton genotypes, while the absence of trichomes was repellent to the caterpillars. There is polymorphism among cotton genotypes to attractiveness to the pest, and the genotypes with antixenosis can be used in future study in plant breeding program as donor source of resistance to S. frugiperda