OPTIMIZATION OF STERILIZATION CHEMICALS AND GROWTH REGULATORS ON IN-VITRO SHOOTING AND ROOTING OF Aloe pubescens REYNOLDS

Abstract

Aloe pubescens Reynolds is one of the endemic endangered Aloe species in eastern highlands and lowlands of Ethiopia, and its propagation for conservation, medicinal, other industrial purposes is not well known. Thus, this research was carried out to optimize the concentrations and durations of chemicals for sterilization of explants, concentrations of NAA and BAP for, in-vitro propagation,and survival rates of regenerated plants on different media under glass house conditions. The sterilization of shoot tip and leaf segment as explants, three concentrations of bavistin (0.1, 0.2, 0.3%) for three time durations (20, 15, and 10 minutes) and three concentrations of mercuric chloride (HgCl2) for three-time durations (15, 10, and 5 minutes) in factorial combination. The inv-itro shoot regeneration consisted of 32 treatments in factorial combination viz. two explants in full-strength MS media enriched with four concentrations of NAA (0,0.25,0.5,1 mg L−1) and BAP (0,1,2,4 mg L−1). The rooting experiment was conducted with half-strength MS medium supplemented with three concentrations of IBA (0.5, 1 and 2 mgL−1) and NAA (0.25, 0.5 and 1 mgL−1) along with control. All the three experiments were conducted in Complete Randomized design with factorial arrangement and replicated trice at plant biotechnology laboratory of Haramaya University. The plantlets were first acclimatized in sterilized soil under the growth chamber followed by acclimatization glass house in a pots filled with sand +soil (1:1); sand + compost (1:1); and sand + soil + compost (1:1:1). The results of sterilization showed that percentages of dead, infected, survival and healthy disinfected explants were significantly influened by bavistin, HgCl2 interaction of these two factors and interaction of explants and bavistin. The interaction of the three factors (explants, bavistin and HgCl2) had significant effect on percentages of infected and healthy disinfected explants. All the parameters of shoot initiation and multiplication from direct in vitro propagation were significantly influenced by NAA and BAP and combination of the two hormones. No of dead and all survival explants were registered by sterilization with HgC12 at concentrations of 0.05% and 0.2% for 15 and 5 minutes, respectively, The highest dead (80%) and lowest survival (20%) explants were registered by sterilization with bavistin at concentration of 0.3% for 10 minutes in combination with HgC12 at concentration of 0.2% for 5 minutes. All the treatments except control and BAP alone at concentration of 4 mgL-1 result 100% and 91.67% shoot initiation. The combination of BAP at 1, 2 and 4 and NAA at 0.5 mgL-1 and BAP alone at 2 mgL-1 concentration produced significantly higher shoot per explants (3 to 4). The shortest days to rooting (18 days) was observed due to the half-strength MS medium enriched with control while the maximum days (24 days) was observed by application of IBA at 0.5 mgL-1 concentration. Total survival of microprpagted plantlets was observed during acclimatization at growth chamber and at glass house except 50% survival observed at pots filled with 1:1 ratio of compost and sand. Although shoot and root regenerations were successful it was concluded that it is vital to conduct further experiments to establish protocols for in vitro propagation of Aloe pubescens Reynoids by including more than two explants and PGR for invitro propagation