Enraizamento in vitro e aclimatação de microplantas de mandioquinha-salsa (Arracacia xanthorrhiza Brancroft)

Abstract

Arracacia xanthorrhiza Bancroft is a tuberous vegetable that has a high nutritional and commercial value, with Brazil being the world's largest producer. The propagation of this species occurs vegetatively, which sometimes presents problems related to the health of the seedlings. One of the alternatives found is the production of seedlings through tissue culture. Therefore, it is necessary to study effective micropropagation protocols. The objective of this work was to determine an in vitro rooting protocol for parsnip (Arracacia xanthorrhiza Bancroft) cultivar BRS Rubia 41, aiming at establishing an ex vitro culture. For that, four in vitro rooting tests (tests 1 to 4) and one acclimatization test (test 5) were conducted. In test 1, in vitro rooting was evaluated in response to five concentrations of AIB auxin (0,0; 3,0; 6,0; 9,0; 12,0 mg L-1) and two culture media (B5 complete and B5 50% of the concentration). In test 2, in vitro rooting was evaluated in response to two concentrations of AIB (0,0 and 2,5 mg L-1) and two culture media (B5 complete and B5 50% of the concentration) with and without activated charcoal (1,0 g L-1). In test 3, in vitro rooting was evaluated in response to five concentrations of AIB auxin (0,0; 3,0; 6,0; 9,0; 12,0 mg L-1) with and without activated charcoal (1 g L-1). In test 4, in vitro rooting was evaluated in response to different combinations of AIB and BAP (0:0; 6:6; 12:0 mg L-1 respectively). Trial 5 studied was ex vitro acclimation in response to different substrate composition (substrate Plantmax® + rice husk; substrate Plantmax® + coconut fiber powder). The variables studied in the in vitro tests (1, 2 and 3) were: number of roots (NR), length of the largest root (CR), presence of callus (PC). In the in vitro test 4, in addition to the above characters, the number of shoots (NB), number of leaves (NF) and plant height (AP) were evaluated. In the 5 ex vitro test, the evaluated characters were: number of green leaves (NFV), shoot length (CPA), number of roots (NR), length of the largest root (CR), number of shoots (NB), number of senescent leaves (NFS) and percentage of survival (%SOB).The experiments were conducted in a completely randomized design and compared using Tukey's test at 5%. For callus formation, the Kruskal-Wallis non-parametric test was used. The 50% reduction in the concentration of salts in the B5 culture medium does not favor rooting. Thus, for the culture of parsnip, the best culture medium for in vitro rooting is whole B5. Activated charcoal does not contribute to better rooting. The combination of whole culture medium B5 and hormone balance 12:0 mg L-1 provides a greater number of roots. However, for root length, the best result is the same culture medium, but without growth regulator (0:0 mg L-1). For acclimatization, the substrate + coconut fiber was the best, where it presents the best performance both in terms of survival rate, as well as shoot length, number of roots and root length.