Strategies to reduce costs in in vitro cultivation of two species of Melocactus (Cactaceae)

Abstract

Melocactus glaucescens and Melocactus paucispinus (“cabeça-de-frade”) are native cacti threatened with extinction, primarily due to their exclusively extractive exploitation for their ornamental potential. Studies have shown that plant tissue culture techniques favor the growth of these species and enable large-scale seedling production. Therefore, they can be used as an alternative to reduce extractive pressure on natural populations of these species. The objective of this study was to analyze the effectiveness of replacing agar with cornstarch, potato starch, or cassava starch; potassium nitrate P.A. (KNO₃) with potassium saltpeter; and autoclaving for chemical sterilization of the culture medium on the in vitro growth of “cabeça-de-frade”. In addition to presenting high contamination levels, the culture media containing potato and cassava starch gelling agents did not present sufficient gel firmness to maintain erect plants. No significant differences were observed in survival, contamination, longest root length, shoot length and diameter, and total dry matter between plants grown in agar, KNO₃, and autoclaving and those grown in cornstarch, potassium nitrate, and chemical sterilization. Therefore, we suggest replacing the agar entirely with 60 g L^-1 of cornstarch, replacing the KNO₃ with 7 g L^-1 of potassium nitrate, and replacing autoclaving with chemical sterilization of the culture medium. This would reduce the costs of in vitro cultivation of the studied species and encourage their propagation for the ornamental market.