Tithonia diversifolia (Asteraceae) uma planta invasora: reprodução, ecologia, diversidade genética e manejo com herbicidas

Abstract

Tithonia diversifolia (Asteraceae) is an exotic invasive species of global concern. The species is present in Brazilian biomes, threatening native ecosystems and cultivated areas. Therefore, five studies were developed with the following objectives: 1. To evaluate the reproductive potential, viability, and seed bank of T. diversifolia accessions collected in the state of Minas Gerais; 2. To evaluate the ecophysiological adaptation of different T. diversifolia accessions; 3. To analyze the genetic diversity of T. diversifolia accessions 4. To evaluate the competitive capacity of T. diversifolia on the physiological responses, nutrient utilization, and initial growth of Astronium urundeuva and Astronium fraxinifolium; 5. To evaluate the effectiveness of herbicides used pre- and post-emergence in controlling T. diversifolia. T. diversifolia plants produce up to 36,528 seeds per plant. The seeds showed germination rates of 96% to 67%, with variation among accessions, and were viable and vigorous according to the tetrazolium test. Seed dispersal was restricted to shorter distances, confirming their potential to colonize monospecific areas. Photosynthetic rate did not differ among T. iversifolia accessions. However, based on water use efficiency, chlorophyll a and b, quantum efficiency, chlorophyll fluorescence, and electron transport rate, it was possible to distinguish accessions with superior invasive capacity, due to their greater growth and physiological efficiency. The T. diversifolia genotypes studied showed a high level of genetic diversity, with 98.08% polymorphism, with accessions originating from Bahia being more dissimilar when compared to accessions collected in Minas Gerais. These results may indicate a high evolutionary potential for the species' adaptation to new environments. T. diversifolia plants exhibit highly competitive capacity over A. urundeuva and A. raxinifolium. There was a reduction in the values of physiological variables and nutrient accumulation in A. urundeuva and A. fraxinifolium plants maintained in coexistence with T. diversifolia. This coexistence had negative effects on the growth of native trees, confirming the existence of competition. Pre- and early post emergence control of T. diversifolia reached 100% with the use of Atrazine, Oxyfluorfen, or Fomesafen. The herbicides glyphosate, 2,4-D, and picloram are effective in controlling T. diversifolia in both the juvenile and adult stages of the invasive plant. The reproductive capacity, genetic diversity, and competitive ability of T. diversifolia reinforce concerns about the species as a threat to native cosystems and cultivated areas.