Germinação e morfogênese in vitro de Plinia peruviana (POIR.) Govaerts (myrtaceae): uma análise morfoanatômica da calogênese e da embriogênese somática

Abstract

Plinia peruviana (Poir.) Govaerts popularly known as jabuticabeira is a species native to Brazil and belonging to the Myrtaceae family. An obstacle found for the commercial production of seedlings is their propagation, being considered difficult to cultivate when propagated by seeds (due to asynchrony in the development of seedlings, long juvenile period and seeds with recalcitrance characteristics) or through conventional vegetative propagation (rates rooting rates obtained are moderate to low, in addition to the absence of studies focusing on the long-term development of seedlings in the field). There is a prospect of growth in commercialization and use by industries, with that studies related to the propagation and conservation of the species become necessary. Thus, this thesis is structured in three chapters. Chapter I presents a literature review, updating the state of the art in the use of biotechnological tools in Plinia spp., emphasizing the need to use molecular approaches to resolve taxonomic uncertainties between species and the establishment of in vitro propagation protocols to overcome the difficulties related to its cultivation. Chapter II focuses on seed germination and in vitro callogenesis, in addition to the morphoanatomical characterization of calluses. For in vitro germination, seed disinfestation methods were tested (with 70% alcohol, NaOCl and autoclaved ultrapure water), and for callogenesis explant sources (nodal segments and leaf discs) and combinations of NAA (naphthaleneacetic acid) and BAP (6 - benzylaminopurine). There was success in the establishment of jabuticabeira seedlings from in vitro germination, indicating 70% alcohol for 2 minutes and triple rinsing in autoclaved ultrapure water for seed disinfestation, promoting the best GSI and with 98% germination. Callogenesis and rhizogenesis in nodal segments occurred both in the absence and presence of PGRs (NAA and BAP), and in leaf discs only with the addition of PGRs in the culture medium, in concentrations equal to or greater than 5.40 µM of NAA + 0 .44 µM BAP. The calli obtained showed non embryogenic characteristics, with large, disorganized and vacuolated parenchyma cells. Chapter III aims at the induction of somatic embryogenesis (ES) from explants obtained from mature seeds, testing concentrations (10, 20 and 30 µM) of 2,4-D and exposure times (1, 3, 5 and 7 days), in addition to the morphoanatomical and ultrastructural characterization of somatic embryos and/or calluses. The formation of somatic embryos occurred directly in the explants (without the need for callus formation), asynchronously and with the development of some anomalous embryos, in addition to the occurrence of repetitive somatic embryogenesis. SE was dependent on the addition of 2,4-D in the culture medium, with emphasis on the concentration of 20 µM of 2,4-D for 5 days of exposure, which promoted the percentage of formation of 26.66%. With the anatomical and ultrastructural analyses, the embryos were characterized at different stages of development and it was possible to identify some abnormalities (fused embryos, absence or formation of only one or multiple cotyledons, absence or little development of procambial cells, abnormal cotyledons and no meristem formation apical). Callogenesis was dependent on the addition of 2,4-D in the culture medium, and the concentration of 20 µM of 2,4-D for 1 day of exposure was the most promising. The calli showed different morphology and coloration with the presence of non-embryogenic cells. The analyzes developed in the present study can contribute to the improvement of new in vitro propagation protocols in P. peruviana.