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

Cattleya warneri , an orchid with 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 and plant growth regulators (PGRs): 6-benzyladenine (BA) and α-naphthaleneacetic acid (NAA) on the in vitro propagation of C. warneri using protocorms as explants. Entire protocorms and sectioned transversely into two halves: apical and basal or longitudinal halves were grown on MS culture medium, with the concentration of macronutrients reduced by half (MSM/2) containing D. subspicatus biomass or extract and BA and/or NAA. The results indicated that the apical halves of protocorm 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. warn eri was achieved using apical halves of protocorms, and MSM/2 medium supplementation with biomass or extract of D. subspicatus is an effective alternative to replace conventional PGRs.