ABSTRACT. The genus Brachiaria contains species that have great economic importance in the Brazilian agricultural sector, as they enable cattle ranching on acid and poor soils with species that are resistant to spittlebugs and form crop-livestock-forest integration systems. The genus mainly consists of tetraploid (2n = 4x = 36) and apomictic species such as B. decumbens and B. brizantha. Sexuality is found in diploid species (2n = 2x = 18) such as B. ruziziensis. Interspecific hybridization between species of interest is possible by the artificial tetraploidization of B. ruziziensis and the subsequent hybridization with genotypes of B. brizantha and B. decumbens. Therefore, tetraploidized plants have to have normal meiosis or low rates of irregularities, as well as produce viable pollen grains. The objective of this study was to compare meiosis and pollen grain viability and morphology in artificially tetraploidized B. ruziziensis with that of descendants generated from crossing and selfing. The frequency of meiotic abnormalities ranged from 4.43 to 11%, and pollen viability ranged from 61 to 85%. Abnormalities were detected from prophase I to the tetrad stage with a variable frequency between the genotypes. The meiotic behavior of the artificially tetraploidized plants was little affected, and the pollen viability of the genotypes was high. Regarding pollen grain ultrastructure, there were no variations or morphological changes in the different genotypes. The genotypes have meiotic stability and high pollen viability, and can be incorporated into Brachiaria breeding programs.

Tuta absoluta is a pest of importance: quick to disperse and difficult to control due to the cases of resistance to insecticide active ingredients. Thus, studies using essential oils (EOs) to search for new molecules should be intensified. The objective of the present study was to evaluate the toxicity of EOs from Citrus aurantifolia (lime), Citrus aurantium (petitgrain) and Citrus aurantium bergamia (bergamot) and its major compounds against T. absoluta in a topical application test. Additionally, the demographic parameters of T. absoluta were studied after the topical application of EOs. The median lethal time (LT50) of the population was 12h for the three EOs tested. The median lethal concentration (LC50) was 33.75, 38.78 and 35.05 µg µL−1 for C. aurantifolia, C. aurantium and C. aurantium bergamia, respectively. As found using gas chromatography coupled to mass spectrometry (GC-MS) quantification, 44.74% of the EO of C. aurantifolia is α-terpineol, while 55.45% and 58.12% of the EO of C. aurantium and C. aurantium bergamia, respectively, is linalyl acetate. The toxicity of the major compounds was tested at concentrations equivalent to the LC50 of the EOs, that is, 16.2 µg µL−1 for α-terpineol, and 25.8 µg µL−1 for linalyl acetate, using topical application. Both of the major compounds showed less toxicity than the EOs. In the sublethal effects tests, all the EOs negatively affected the demographic parameters of T. absoluta, with a decrease in the duration of larval instars, duration of the pupal period, fecundity, oviposition and viability of the eggs, implying a reduction in the population growth parameters of this pest. The EOs of lime, petitgrain and bergamot are toxic to T. absoluta, and low concentrations cause deleterious effects on the reproductive and population parameters of T. absoluta.

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