Effect of microalga Desmodesmus subspicatus, polyamines and plant growth regulators on the in vitro propagation of Cattleya warneri

Abstract

Abstract Cattleya warneri, an orchid with high ornamental potential, suffers indiscriminate harvest and is classified as a vulnerable species, requiring propagation studies. The aim of this study was to evaluate the effect of biomass or aqueous extract of Desmodesmus subspicatus microalga, polyamines (PAs) and plant growth regulators (PGRs): 6-benzyladenine (BA) and α-naphthaleneacetic acid (NAA) on the in vitro propagation of C. warneri using the thin cell layer (TCL) technique. Entire protocorms and transversal sections (tTCLs) or longitudinal sections (lTCLs) were grown in MS culture medium, with the concentration of macronutrients reduced by half (MSM/2) containing D. subspicatus biomass or extract Pas, and BA and/or NAA. The results indicated that the apical tTCLs were the best explants and the entire protocorms formed seedlings. The regeneration of protocorm-like bodies (PLBs) was more efficient with the addition of 1.5 g L− 1 of microalgae biomass (92% and 4.7 PLBs) or 1.0 g L− 1 of extract (100% and 3.3 PLBs) and 8 µM BA (89% and 5.2 PLBs). The biomass (1.0 g L− 1) or extract (2.0 g L− 1) also enabled PLBs regeneration from entire protocorms (70% and 4.0 PLBs, 50% and 3.2 PLBs, respectively). The plant acclimatization was recommended using coconut fiber and vermiculite (1:1, v/v) as substrate (survival rate 84%% and greater fresh mass 0.895 g). In conclusion, a rapid and efficient protocol for the mass propagation of C. warneri was achieved using the TCL technique. In addition, MSM/2 medium supplementation with biomass and extract of D. subspicatus is an effective alternative to replace conventional PGRs.