Propagación In Vitro Mediante Hipocotilo

In Vitro Cell.Dev.Biol.—Plant (2007) 43:9–15
DOI 10.1007/s11627-006-9009-2

DEVELOPMENTAL BIOLOGY/MORPHOGENESIS

High-frequency plant regeneration through adventitious
shoot formation in castor (Ricinus communis L.)
Yeh-Jin Ahn & Louisa Vang & Thomas A. McKeon &
Grace Q. Chen

Received: 13 October 2006 / Accepted: 14 October 2006 / Published online: 9 February 2007 / Editor: T.J. Jones# The Society for In Vitro Biology 2007

Abstract An efficient plant regeneration protocol was
established for castor (Ricinus communis L.). Hypocotyl
tissue from zygotic embryo axis produced adventitious
shoots when treated with either thidiazuron (TDZ, 1 μM) or
6-benzylaminopurine (BA, 20 μM). TDZ resulted in more
than a threefold higher rate of shoot induction (a maximum
of 24.2 shootsper explant) than BA (6.8 shoots). Our
results also showed that the pretreatment of explants in the
dark increased the number of shoots regenerated per
explant by 82% and 36% with TDZ and BA, respectively.
The elongation of hypocotyl tissue in the dark appears to be
the primary cause of the increase. Comparable rates of
rooting were achieved on the media supplemented with
eitherindole-3-butyric acid (IBA, 84.3%) or 1-naphthaleneacetic acid (NAA, 87.4%) at 5 μM. However, IBA was
more efficient in promoting root and shoot development,
resulting in a higher rate of establishment (93.5%) in the
soil, compared to the rate with NAA (39.5%). Histological
analysis showed the adventitious induction of the shoot
buds originated from the cortex of the hypocotyl tissue.
Keywords Darkpretreatment . Hypocotyl . Plant tissue
culture . Thidiazuron
Y.-J. Ahn : L. Vang : T. A. McKeon : G. Q. Chen (*)
Agricultural Research Service, Western Regional Research Center,
U. S. Department of Agriculture,
800 Buchanan Street,
Albany, CA 94710, USA
e-mail: qhgc@pw.usda.gov
Present address:
Y.-J. Ahn
College of Natural Sciences, Division of Life Sciences,
Sangmyung University,
7Hongji-dong, Jongno-gu,
Seoul 110-743, Republic of Korea

Introduction
Castor (Ricinus communis L.) is a member of the Euphorbiaceae or spurge family, mostly native to the tropical and
subtropical regions (Weiss, 2000). It is an important oil
crop containing approximately 60% oil in its seeds. The
highly versatile castor oil and its derivatives have a number
of industrial uses, includinghigh-quality lubricants, paints,
plastics, and coatings (Moshkin, 1986). In world trade,
India is the largest castor oil producer, representing 85% of
production, followed by China and Brazil (Weiss, 2000).
However, despite the high industrial demand, the United
States no longer grows castor commercially; its cultivation
poses serious health concerns due to the presence of the
ricin toxin(reviewed in Lord et al., 1994; Hartley and Lord,
2004) and hyperallergenic 2S albumins in its seeds
(reviewed in Pastorello et al., 2001; Shewry et al., 2002).
Ricin toxin inactivates ribosomes by cleaving the Nglycosidic bond between an adenine and ribose in 28S
rRNA, thus inhibiting protein synthesis (Endo and Tsurugi,
1987). 2S albumin was identified as the major allergen of
castor seeds byThorpe et al. (1988). A total of 96%
castor-sensitive patients had the IgE antibody that was
specific to the 2S storage albumin.
Genetic engineering appears to be an effective approach
to reduce the levels of these hazardous proteins. Therefore,
an efficient regeneration protocol for castor needs to be
established. Castor is extremely recalcitrant to in vitro
regeneration. Most of the earlystudies using vegetative
tissues as explants have proven to be either inefficient or
difficult to reproduce (Reddy et al., 1987; Reddy and
Bahadur, 1989; Sarvesh et al., 1992). Then, researchers
started to focus on meristematic tissues to improve regeneration efficiency (Molina and Schobert, 1995; Lakshmi
and Bahadur, 1997; Sujatha and Reddy, 1998). Sujatha and

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Reddy...