Effect of benzyladenine on the regeneration of two varieties of cactus pear (Opuntia spp.)

Abstract

The cactus pear (Opuntia spp.) is a plant species well adapted to environments with water shortages, due to morphological and physiological adaptations, besides being a great choice of fodder in the dry season. The aim of the study was to establish the optimal concentration of BA to induce shoots in vitro forage cactus varieties F-24 (O. atropes) and F-21 (N. cochenillifera). The explants were cultured on MS medium containing 30 g L-1 sucrose, supplemented with concentrations of BA (0, 0.5, 1.1, 2.2, 4.4, 8.8 µM) and IAA (0.6 µM), solidified with 0.8% agar, pH 5.85. They were kept under controlled conditions of 25 ± 2 °C PAR 30 µmol m-2 s-1 and a photoperiod of 16 hours light and 8 hours of dark. The sprouting was performed at 30 and 60 days after inoculation. The results indicate variability in responses between the genotypes at concentrations of BA. The response to the presence of BA in the percentage of sprouting followed a sigmoid curve. Where the point of maximum efficiency (SME) at 30 days was 3.7 µM BA for variety F-24, and 4.5 µM BA for the F-21. With sprouting percentage of 58% (F-24) and 21% (F-21). SMEs at 60 days was 4.1 µM BA for variety F-24, with 85% sprouting. The F-21 genotype showed significant oxidation in the explants, which prevented its growth after 30 days of cultivation. As well it is recommended to exchange the culture medium every 30 days to prevent oxidation thereof. The concentrations of BA more effective in inducing sprouting palm genotypes were 3.7 µM range for F-24, and 4.5 µM for F-21 variety. However, due to the high oxidation and low percentage of sprouting new tests are required, including the use of antioxidants.