ABSTRACT
Herbicides are commonly used to control weed. However, some plants are resistant to such products. To identify less harmful herbicides, it is crucial to search for different mechanisms of action. Thymol is an easily acquired allelopathic compound, capable of producing its respective semisynthetic derivative, thymoxyacetic acid. The aim of this study was to determine the effects of thymol and thymoxyacetic acid molecules as bioherbicides in greenhouse at the concentration of 3 mmol L-1 in pre- and postemergence applications in five species: Amaranthus viridis L., Cucumis sativus L., Lactuca sativa L., Eleusine indica L., and Sorghum bicolor L. The initial seedling development and DNA changes were analyzed. These molecules were contrasting with the solvent, in the negative control, and with the glyphosate, in the positive control, promoting phytogenotoxic activities. The toxic effect of thymoxyacetic acid was more effective in preemergence and thymol's in postemergence. We also observed a reduction in the germination speed index and root growth with a negative correlation to the increase in potassium leaching. Damage to the root and shoot of the seedlings was verified at the DNA level, and the phytotoxicity of the plants treated with the herbicide glyphosate was similar to the plants treated with the natural molecules tested. The bioherbicidal effect of thymol and thymoxyacetic acid exacerbates the reduction of the environmental impact caused by the disordered and increased use of residual pesticides.
Subject(s)
Herbicides , Thymol , Thymol/pharmacology , Plant Weeds , Herbicides/toxicity , Seedlings , GerminationABSTRACT
Polyploidy is more than two chromosomal sets per nucleus, as the allotetraploid Coffea arabica. Due to allotetraploidy, C. arabica shows different phenotypes compare to diploid Coffea species, highlighting by beverage quality produced from its grains. Looking for the possibility of new phenotypes coupled with economic feature, considerable progress since 60's was reached for synthetic chromosome set doubling (CSD) in vitro, involving especially the antitubulin compounds, biological material, and used tissue culture pathway as the indirect somatic embryogenesis (ISE). Here, we aimed to regenerate autotetraploid and auto-alloctaploid plantlets of Coffea canephora and C. arabica, respectively, from a novel in vitro CSD procedure for Coffea. Exploring the ISE pathway, we treated the cellular aggregate suspensions (CAS) with 0.0 (control), 0.5, 1.5, or 2.5 mM of colchicine solution for 48, 72, or 96 h and maintained in liquid medium under constant orbital shaking. After transferring the CAS to semisolid media for somatic embryo regeneration, we considered it as cellular mass. Mature cotyledonary somatic embryos were only regenerated from cellular masses treated with 2.5 mM/48 h and 2.5 mM/72 h for C. canephora and with 0.5 mM/48 h for C. arabica. Evaluating the DNA ploidy level and the chromosome counting revealed that 36 (34.9%) plantlets of C. canephora were autotetraploids (4C = 2.86 pg, 2n = 4x = 44) and 61 (21.1%) of C. arabica were auto-alloctaploids (4C = 5.24 pg, 2n = 8x = 88). The CSD procedure, exploring the CAS proliferation and ISE pathway, promoted whole-genome duplication and resulted in a relatively high number of solid polyploids of both Coffea species. Due to distinct responses, DNA sequence fidelity (genetic) and global level of 5-methylcytosine (epigenetic) were evaluated. We observed that the increase of 5-methylcytosine levels was associated with somatic embryo regeneration from cells showing DNA sequence fidelity for the tested SSR primers. In conclusion, the adopted procedure for in vitro CSD is reproducible for induction, regeneration and propagation of Coffea polyploids and potentially other shrubbery and woody species. In view of the novelty of this procedure to generate new germplasm, we show the key issues and the steps of the CSD procedure.
ABSTRACT
Bromeliads are an important group for the maintenance of the Atlantic Forest, with many threatened species due to exacerbated extraction and destruction of their natural habitats. Considering the need of developing protocols for the conservation of these species, the aim of this work was to evaluate the effect of different growth regulators in the in vitro induction of shoots of Billbergia euphemiae. Leaf explants were excised from seedlings derived from in vitro germination and grown on MS medium supplemented with NAA (0, 1 or 2 µM) and BA (0, 2, 4 or 6 µ M) combinations. The evaluation of the number of shoots per explant, shoot length, number of leaves per shoot and longest leaf length average was carried out after 30 and 60 days of culture. The best in vitro responses were observed in the presence of 1 µM NAA after 60 days of culture, which induced the best production of shoots per explant (16.39), as well as the highest rates of shoot length (1.08 cm), number of leaves per shoot (5.00) and the longest leaf length (0.56 cm). This work determined the best conditions for shoot production from leaf explants of B. euphemiae, being the first report on micropropagation of this species.
As bromélias constituem um importante grupo para a manutenção da Floresta Atlântica, com várias espécies ameaçadas de extinção pelo extrativismo exacerbado e a destruição dos habitats naturais. Considerando a necessidade do desenvolvimento de protocolos para a conservação destas espécies, este trabalho teve como objetivo avaliar o efeito de diferentes reguladores de crescimento na indução de brotos de Billbergia euphemiae. Explantes foliares foram excisados de plântulas derivadas da germinação in vitro e inoculados em meio MS suplementado com combinações de ANA (0, 1 ou 2 µM) e BA (0, 2, 4 ou 6 µM). O número de brotos por explantes, comprimento dos brotos, número médio de folhas por broto e comprimento médio da maior folha foram avaliados após 30 e 60 dias de cultura. As melhores respostas foram observadas na presença de ANA a 1 µM, após 60 dias de cultura, que induziu a maior produção de brotos por explante (16,39), assim como as maiores taxas de comprimento dos brotos (1,08 cm), número médio de folhas por broto (5,00) e comprimento da maior folha (0,56 cm). Este trabalho determinou as melhores condições para produção de brotos de B. euphemiae a partir de explantes foliares, representando o primeiro relato de micropropagação desta espécie.
Subject(s)
Bromelia , In Vitro Techniques/methods , Germination , Agricultural Inoculants , Organogenesis, PlantABSTRACT
The molecular characterization of ten genotypes of the Coffea arabica plants and of seven genotypes of C. canephora having interesting features for coffee breeding programs was carried to select the parents for breeding. A total of 40 SSR and 29 ISSR primers were used. The primers generated a total of 331 (307 polymorphic and 24 monomorphic) bands. Analysis of genetic diversity presented dissimilarity intervals ranging from 0.22 to 0.44 between the Conilon genotypes, from 0.02 to 0.28 between the Arabica genotypes, and from 0.49 to 0.60 between the genotypes of the two species in the joint analysis. Four groups were formed: I = genotypes of C. arabica, II = four progenies of C. canephora, Conilon group, and one non defined C. canephora (Conilon or Robusta), III = one progeny of un-defined C. canephora (Conilon or Robusta) and IV = one progeny of C. canephora of Robusta group. The grouping formed was consistent with the origins of each group. High stabilities of the bifurcations were found by bootstrap analysis. The use of molecular markers of the SSR and ISSR types in the diversity study was efficient in distinguishing genotypes between and within C. arabica and C. canephora. .
