Establishment of high effective regeneration and propagation system for ornamental crabapple (Malus spp.)
In order to establish efficient regeneration system for ornamental tissue culture, we used Malus spp. ‘Indian Magic as the experimental materials and investigated the effects of disinfection and antibrowning agents, culture mediums and hormones proportion on differentiation, multiplication, callus induction and rooting, and also the effects of culture substrates on growth of transplants in greenhouse. The results showed that, the selection of stem tips without scale as the tissue culture material and the employment of HgCl2 5+3 min two-step method for stem tip disinfection could reduce contamination rate and the addition of 2.0 g/l PVP (polyvinylpyrrolidone) could effectively prevent the browning of culture medium and explants. When the three kinds of culture medium were fixed [Murshige and Skoog (MS) containing 1.0 mg/l 6-BA (6-benzyladenine) plus 0.01 mg/l NAA (anaphthaleneacetic acid), MS containing mg/l 6-BA plus 0.2 mg/l NAA and 1/2 MS containing 0.2 mg/l NAA] on inducing differentiation, multiplication and rooting, the differentiation rate, multiplication coefficient and rooting rate increased to 81.2, 6.13 and 100%, respectively. At the same time, leaves callus induction rate reached 100% on the medium of MS containing 1.5 mg/l 6-BA plus 1.0 mg/l 2,4- D(2,4-dichlorophexoxyace-tic acid) and adventitious shoots were directly regenerated from leaves on MS containing 1 mg/l 6-BA plus 0.1 mg/l NAA. The survival rate of the transplants was up to 95% and seedlings grew well after the transplant to the substrates containing vermiculite and perlite (1:1) in the greenhouse under relative humidity of 80 to 85%, temperature of 25 ± 2°C, light intensity of 1500 to 2000Lx and mist spraying condition. Based on the stated, we determined a technical framework of the leaves callus induction and regeneration for crabapple tissue culture, in which both the types and concentrations of hormones added in the medium played most important roles.
Key words: Malus spp., regeneration, callus induction, propagation, hormones.