Caracterização de sementes e micropropagação de guapeva [Pouteria torta (Mart) Radlk]

Abstract

Pouteria torta (Mart) Radlk is a fruit plant of great medicinal value from the Cerrado biome. Its seeds are recalcitrant and cannot be stored. There are little studies regarding its in vitro and ex vitro propagation. Based on this, we aimed at characterizing their seeds and establish a protocol for the micropropagation of the species. To characterize the seeds, we evaluated water content, weight of one thousand seeds, morphological and chemical characteristics, and determined the imbibition curve. For the in vitro establishment, we evaluated the effect of the presence and absence of light and the germination speed index (GSI). For in vitro multiplication, we evaluated the effect of adding 6-benzylaminopurine (BAP), benzyladenine (BA) and thidiazuron (TDZ) (0, 0.25, 1, 4 and 16 µM). We also evaluated, separately, the use of zeatin (0, 2.3, 4.6, 9.2, 18.4 and 36.8 µM) and phloroglucinol (0, 80, 396 and 792 µM), added to the WPM culture medium. For in vitro root formation, we verified the effect of naphtaleneacetic acid (NAA) and indolbutyric acid (IBA) (0, 1, 5 and 10 µM). For ex vitro rooting, we used IBA (500, 100 and 1500 µM). The explants, rooted in vitro and ex vitro, were acclimatized in tubes containing Trosptrato ® . The results showed that the seeds presented 38.4% water content, showing recalcitrant behavior. We determined that one thousand seeds weighed, approximately, 2.4 Kg presenting starch as main source of reserve. Seed area was of 2.5 cm -3 , with, approximately, 2.5 x 1.3 cm diameter. Germination began around day 22, with no physical dormancy of the seeds. In vitro germination began at day 9. Embryo germination did not depend on the presence of light. However, we verified that light promotes higher GSI. The use of BAP, BA and TDZ induced callus formation of, approximately, one shoot per explant. There was no root formation in explants rooted ex vitro, with consequent death of the explants. The use of 5 and 10 µM IBA promoted higher in vitro rooting, and IBA was prominent in the formation of a higher number of roots per explant. The acclimatization of the explants was 90% successful.