Development of the prickly pear cactus Opuntia stricta (Haw.) Haw. (Cactaceae) in vitro in response to the replacement of potassium nitrate for a commercial kno 3 fertilizer

Abstract

In micropropagation, potassium nitrate (KNO3), an ACS reagent grade chemical, used in the preparation of growing mediums is expensive and its procurement depends on bureaucratic procedures, as it is controlled by the Brazilian Army. This research to assessed the effect of replacing the ACS KNO3 for a commercially available fertilizer (KNO3- based) on the micropropagation of the prickly pear cactus (Opuntia stricta (Haw.) Haw. cv. Elephant Ear. Treatments used six different fertilizer concentrations (0, 0.5, 1, 1.5, 2 and 2.5 g L-1) and a control consisting of 1.9 g L-1 KNO3, as shown in the MS salts. The survival, size and number of sprouts and the value of fresh biomass were evaluated. After seedling acclimation, we assessed the survival, number of sprouts, length, and number of roots, racket formation, average fresh biomass mass, macronutrient absorption and morphological changes of the seedlings. Explants inoculated with fertilizers at concentrations of 0.0; 2.0 and 2.5 g L-¹ did not grow. The response of explants at concentrations of 0.5 and 1.5 g L-1 of the fertilizer were the same as those developed in a KNO3 medium, and at a concentration of 1.0 g L-1, in all variables, the means were higher than those of the control medium. Therefore, it showed the feasibility of using fertilizers in the in vitro cultivation of the prickly pear cactus, which may remove bureaucratic barriers and reduce product costs by 99.12%.

Micropropagation of Opuntia and Other Cacti Species Through Axillary Shoot Proliferation: A Comprehensive Review

“…Numerous culture media formulations have been used for plant micropropagation through axillary bud proliferation. The few earlier studies conducted on Opuntia genus have used MS medium (Estrada-Luna et al, 2008 ; Angulo-Bejarano and Paredes-López, 2011 ; Zoghlami et al, 2012 ; Ghaffari et al, 2013 ; Vidican, 2015 ; Ferreira et al, 2021 ; Mabrouk et al, 2021 ). It is widely admitted that salt formulation plays a crucial role in the prickly pear shoot initiation and development.…”

“…Potassium nitrate triggers the induction and the differentiation process of the aerial parts, and it plays the role of osmoregulator. Ferreira et al ( 2021 ) induced shoot formation in O. stricta using a commercial nitrogen fertilizer instead of potassium nitrate and showed that MS medium can be amended with 1 g/L of a potassium nitrate-based fertilizer (Ferreira et al, 2021 ). Clayton et al ( 1990 ) suggested the potential of other media formulations.…”

“…Beneficial effects of cytokinin–auxin on shoot elongation have also been reported in other Opuntia species. Ferreira et al ( 2021 ) recorded the highest O. stricta shoot length values while cultivating newly formed shoots in the presence of 1.5 mg/L of BA and 0.0625 mg/L of NAA. Thus, the combination of low-to-moderate concentrations of cytokinins and low auxin amounts is required for a great shoot elongation for Opuntia genus.…”

“…Besides plant growth regulator concentrations, shoot elongation was found to be species-dependent ( Table 3 ) and sprout lengths are highly variable ( Table 3 ). For O. ficus-indica , the best PGR treatments allowed the elongation of newly formed shoots to reach a maximum of 50 mm (Zoghlami et al, 2012 ), while the highest shoot elongation was 60% and 80% lower for O. stricta and O. ellisiana shoots (i.e., 20 and 10.2 mm, respectively) (Juárez and Passera, 2002 ; Ferreira et al, 2021 ).…”