Interação Diabrotica speciosa e genótipos de Phaseolus vulgaris: preferência alimentar e tabela de vida

Abstract

In this study, we evaluated the interaction of Diabrotica speciosa (Germar) (Coleoptera: Chrysomelidae) and six commercial cultivars of bean (Phaseolus vulgaris), in order to characterize antixenosis and/or antibiosis resistance. The cultivars BRS Campeiro, IPR Uirapuru, BRS Esplendor, IPR Tuiuiu, IPR Tiziu and FTS Soberano were grown in the greenhouse and used in laboratory bioassays. To evaluate antixenosis, free-choice bioassays were performed in petri dishes, releasing six newly emerged adults of D. speciosa and offering to them six leaf discs (30 mm diameter), one of each cultivar, during 24 hours. In addition, no-choice bioassays were performed in plastic containers whith a leaf disc (30 mm diameter) of each cultivar were offered as the only source of food to one adult. Each foliar disc were evaluated before and after consumption by D. speciosa, registering the area damaged. The antibiosis was evaluated in insects biology studies, which were done in plastic cages with one newly-emerged couple (N=30), registering the survival and oviposition of adults at intervals of 48 hours.The leaf trichomes were analyzed, inserting 20 leave`s seccions (1 mm²) in scanning electron microscope, and registering the number of hookedtrichomes, acicular trichomes and glandular trichomes on abaxial (N = 10) and adaxial (N = 10) surfaces. In free-choice bioassays adults showed less preference to cultivars IPR Tuiuiú, IPR Uirapuru, BRS Esplendor, consuming less leaf area. On the other hand, in no-choice bioassays insects also fed up all cultivars, and the consumption area was similar. The isolated analysis of biological parameters did not differ among the insects that fed the different genotypes. From the fertility life table it was obtained difference in the mean interval between generations (IMG) as the BRS Esplendor genotype showed a lower average range compared to BRS Campeiro. And the net reproductive rate (Ro) of BRS Campeiro genotype differed from the others because the insects fed with this genotype showed higher reproduction. As to the trichomes, IPR Tuiuiu genotype had the lowest density acicular trichomes on the adaxial side face, and the glandular trichomes and hooked did not differ in the side faces of leaves. In the leaf center BRS Campeiro genotypes IPR Tuiuiu and BRS Esplendor had the greatest density of glandular trichomes in adaxial face, and in the abaxial face only the BRS Campeiro and the IPR Tuiuiu remained with higher density of this tricoma followed by IPR Tiziu. For acicular trichomes BRS Campeiro differed presenting the lowest density in the face adaxial. Hooked trichomes showed higher densities in the abaxial face of genotypes IPR Tiziu, and IPR Tuiuiu and IPR Uirapuru. The total trichomes (adaxial + abaxial) did not differ between the genotypes on the side, but the center genotypes IPR Tiziu, IPR Tuiuiú and IPR Uirapuru were the densest. In this study, there were no differences that can say resistance to D. speciosa in the evaluated treatments, however it was obtained are presented important information about the feeding behavior of the bean resistance to D. speciosa in bean and life table, which may provide a basis for future work in the area.