Resistência de genótipos de arroz à Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera: Noctuidae)

Abstract

Rice (Oryza sativa L.) is one of the foods most consumed by the world population. Among the various pests that limit its productivity and compromise the rice quality, the leaf caterpillar Spodoptera frugiperda (J. E. Smith, 1797) deserves special mention. The objective of this work was to evaluate the resistance of rice genotypes to S. frugiperda, and to generate information on the use of resistant plants as a component in integrated pest management. The research was developed in the Agricultural Entomology Laboratory of the Goiano Federal Institute - Campus Urutaí, in Urutaí, Goiás, Brazil. Eighteen rice genotypes were evaluated, including 17 traditional varieties and a variety obtained from external breeding (IR 64). Antioxiosis tests, antibiosis and nutritional parameters were performed under controlled conditions of temperature (25 ± 2 ° C, relative humidity 60 ± 10% and photophase 14 hours), and tolerance in the greenhouse. In the first experiment the antixenosis was evaluated, determining the number of S. frugiperda caterpillars attracted by plants at different times, and the attractiveness index in test with and without choice. The experimental designs were randomized blocks for the test with a chance of choice and completely randomized for the test with no chance of choice, all with 10 repetitions. For the biological parameters experiment, a completely randomized design was used, with 32 replications. It was evaluated: a) Larval phase: viability, caterpillar weight at 10 days after hatching, and the duration of the stage; b) Pre-pupal phase: feasibility, stage duration; c) Pupal stage: viability, pupal weight at 24 hours and duration of the stage; d) Adult phase: sexual ratio, stage duration, and longevity; e) total life-time, total viability, and longevity of males and females. For the nutritional parameters test, a completely randomized design was used, with 10 replicates. It was evaluated: ingested, assimilated and metabolized food rates, weight gain, relative consumption rate, relative metabolic rate, relative growth rate, approximate digestibility, feed conversion efficiency, digestible feed conversion efficiency, and cost metabolic. For the tolerance test, the experimental design was completely randomized, with 18 treatments (genotypes) and four replications, arranged in a factorial scheme (infested plants and control). It was determined: a) insects recovered; b) number of tillers; c) stem diameter; d) height of the stem; (e) fresh mass of the aerial part; f) fresh root mass; g) aerial shoot dry mass; and h) dry mass of the root. The genotypes Miúdo Branco (BGA 012626) and Arroz do Governo (BGA 011335) showed antixenose resistance to S. frugiperda. And the genotypes IR 64 (BGA 018794) and Bacaba Branco (BGA 011352) presented antibiosis resistance. Meanwhile, genotypes IR 64 (BGA 018794), Arroz do Governo (BGA 011335), Nenenzinho (BGA 011585), and Trinca Ferro (BGA 011391) showed resistance to S. frugiperda tolerance. These genotypes can be used in rice breeding programs aimed at incorporating sources of resistance to this pest, and used by farmers as a tool for integrated pest management.