Báo cáo khoa học: Effects of sustained subculture on apparent rejuvenation of the apple rootstock M.9 in vitro and in vivo

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Báo cáo khoa học: "Effects of sustained subculture on apparent rejuvenation of the apple rootstock M.9 in vitro and in vivo"Effects of sustained subculture on apparent rejuvenationof the apple rootstock M.9 in vitro and in vivo O.P. JonesC.A. WebsterInstitute of Horticultural Research, East Malling, Maidstone, Kent, U.K. proliferation medium containing 2 mgll BAP proliferationIntroduction (benzylaminopurine), 0.1 mg/I IBA (indole buty- ric acid) and 162 mgli phloroglucinol (PG).Sequential subculture of fruit trees leads These 2 culture lines were subcultured monthly gradual physiological change whichto a for 21 mo along with 2 other culture lines initi-may be termed ’rejuvenation’. This change ated in 1978 and 1982, respectively. In vitro rooting involved transfer for 4 d of single shootsis characterized by a gradual improvement from proliferation medium to MS mediumin shoot production and rooting in vitro containing 3 mg/l IBA, followed by transfer for 3(Jones, 1985). wk to half-strength MS medium without growth Hedges established from micropropa- regulators. Direct rooting involved transfer of single shoots from proliferation medium, dippedgated plants of the plum rootstock Pixy in a powder preparation of 0.2% IBA + 10%(Prunus insititia) continued for at least 9 yr Captan, to sterile horticultural sand for 4 wkto produce shoot cuttings with the juvenile (Webster and Jones, 1989).character of more rapid rooting (Howard Micropropagated plants produced in 1985et al., 1989a). Thus, rejuvenation as a from culture lines initiated in 1978 and 1982 were grown in the glasshouse during 1986 andresult of micropropagation may be ex- transferred to the field in 1987 as hedge plants.ploited to improve conventional propa- Rooting of leafy summer cuttings and leaflessgation of clones which are normally dif- winter cuttings from these micropropagatedficult to propagate. plants was evaluated during 1986-1988 in com- This paper describes the apparent reju- parison with cuttings from conventionally propa-venation in vitro of the apple rootstock M.9 gated plants.and the subsequent retention of juvenilecharacters in micropropagated plants inthe field. M.9 is one of the most frequentlyused apple rootstocks worldwide but suf- Resultsfers from the serious shortcoming of beingdifficult to propagate. Apparent rejuvenation in vitroMaterials and Methods Shoot production with the two 1986 cul- ture lines increased from a mean of 1 newTwo shoot culture lines, A and B, were esta- shoot per single shoot inoculum to aroundblished in 1986 from 2 shoot tip explants on MS5 new shoots with monthly subculture over 57 ± 8.9% in the 1978 source over a 4 wk21 mo. Shoot production of culture line B period as compared with 3 ± 3.3% fromremained significantly higher (PHoward B.H., Jones O.P. & Vasek J. (1989b) (Menhenett R., ed.). British Plant Growth Regu-Growth characteristics of apparently rejuve- lator Group Monograph 13, pp. 113-124nated plum shoots. J. Hortic. Sci. 64, 157-162 Webster C.A. & Jones O.P. (1989) Micropropa-Jones O.P. (1985) The role of growth regulators gation of the apple rootstock M.9: effect of sus-in the propagation in vitro of temperate fruit tained subculture on apparent rejuvenation intrees. In: Growth Regulators in Horticulture vitro. J. Hortic. Sci. 64, 421-428