Diversidade genética e estrutura de populações de Helosis brasiliensis Schott & Endl. (Balanophoraceae) do Rio Grande do Sul

Abstract

Helosis brasiliensis (Balanophoraceae) is a parasitic plant, occurring in the south, southwest and northeast regions of Brazil, associated with the Atlantic Forest Biome. It is found on rocky soils close to streams and in transitional forests, in humid places, with little sunlight and with availability of organic matter. It is popularly known as the spike-of-dragon, and is characterized by being a holoparasitic geophyte herb, with an underground vegetative body, which is attached to the host plant. It has a rhizomatous structure and does not have leaves and roots. Its inflorescence, about 5-10 cm, appears in a short period when the climate is favorable for its emergence. In the literature we find few morphological and molecular studies involving the species. Thus, the objective of this work is to evaluate the genetic diversity and population structure of Helosis brasiliensis from Rio Grande do Sul, as well as to identify the species that can be parasitized by it. Four populations of H. brasiliensis were collected in the municipalities of Silveira Martins, Passa Sete, Candelária and Teutônia, totaling 52 individuals. At the Plant Genetics laboratory, total DNA extractions were performed, followed by PCR reactions using two types of molecular markers for the evaluation of genetic diversity and population structure: the nuclear ribosomal spacer ITS and ISSR. The amplified samples for the ITS region were sequenced and analyzed in Clustal X, MEGA, Structure X and GenAlEx software. Samples amplified with ISSR were visualized on an agarose gel and analyzed in GenAlEx and Structure X software. Samples of photosynthetic tree and shrub plant species were also collected within a radius of 3 meters from the populations of H. brasiliensis for further taxonomic identification of the species. potentially parasitized, in addition to some roots that were close to the individuals of Helosis. Genetic diversity indices were higher within populations than among populations. PCoA analysis revealed five genetic groups in the sampled populations. Individuals in the population of Teutônia divided into two groups. Overall, the species has moderate levels of genetic diversity (I: 0.529) and high polymorphism (89.42%). From the taxonomic analyses, we were able to report that the species under study has in its habitat 6 species from 6 families, namely: Gramineae, Lauraceae, Meliaceae, Piperaceae and Sapindaceae, which were identified in more than one sampling site with a high probability of be hosts of the species in Rio Grande do Sul. It is concluded that H. brasiliensis has high genetic diversity in the populations analyzed. It was still not possible to determine which species are parasitized by Helosis brasiliensis in Rio Grande do Sul, but the results obtained so far suggest that the species can parasitize more than one species of forest plants.