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REVIEW ARTICLE
Red sandalwood (Pterocarpus santalinus L. f.): biology,
importance, propagation and micropropagation
Jaime A. Teixeira da Silva
1
•Mafatlal M. Kher
2
•Deepak Soner
3
•
M. Nataraj
2
Received: 3 November 2017 / Accepted: 6 February 2018 / Published online: 20 June 2018
The Author(s) 2018
Abstract Pterocarpus santalinus L. f. (Fabaceae; red
sanders) is prized for its wood whose colour and fragrance
is due to the presence of santalins that have pharmaceutical
and industrial uses. Red sanders is listed as an endangered
plant species on the IUCN red data list as a result of the
exploitation of its wood and essential oil. This review
emphasizes the pollination biology, seed germination,
vegetative propagation and micropropagation of P. san-
talinus. Excessive use of P. santalinus has also caused the
emergence of various adulterants, so accurate identification
is essential.
Keywords Conservation Fabaceae IUCN red data list
Medicinal plant Micropropagation Red sanders
Historical, cultural, medicinal, and economic
importance of red sanders as a basis
for conservation
Pterocarpus santalinus L. f. (Fabaceae) is most commonly
known as red sandalwood in English, but it also has other
common names in several languages (Table S1). Ptero-
carpus is derived from the Greek words pteron (wing) and
karpos (fruit), referring to the winged pod, while santalinus
originates from the Latin sandal and inus (meaning similar
to), i.e., a plant with characteristics similar to Indian san-
dalwood, Santalum album L. (Botanical Survey of India
2012). Like African or Nepalese sandalwood (Teixeira da
Silva et al. 2016a) and Indian sandalwood (Teixeira da Silva
et al. 2016b), P. santalinus is also prized for its hard, dark-
purple, bitter heartwood (Navada and Vittal 2014). In India,
the natural range of P. santalinus used to be a very restricted
area of 15,540 km
2
in the southeast (Sarma 1993). Cur-
rently, P. santalinus is found exclusively in a well-defined
forest tract of Andhra Pradesh in Southern India (Raju and
Nagaraju 1999; Prakash et al. 2006; Balaraju et al. 2011),
but is also found in the Chinese provinces of Yunnan,
Guangdong and Guangxi, and on Hainan Island, where it is
referred to as zitan (Kaner et al. 2013).
The colour and fragrance of P. santalinus heartwood are
derived from santalins while the pleasent aroma is caused by
the presence of terpenoids (Kumar et al. 1974). A dye pre-
pared from the heartwood of P. santalinus is used as a stain in
light microscopy (Banerjee and Mukherjee 1981;SenGupta
and Mukherjee 1981), as a coloring agent in pharmaceutical
preparations, in food, leather and textile industries (Ankalaiah
The online version is available at http://www.springerlink.com
Corresponding editor: Yu Lei.
Electronic supplementary material The online version of this
article (https://doi.org/10.1007/s11676-018-0714-6) contains supple-
mentary material, which is available to authorized users.
&Jaime A. Teixeira da Silva
jaimetex@yahoo.com
&Mafatlal M. Kher
mafatlalmkher@gmail.com
&Deepak Soner
deepaksoner@gmail.com
&M. Nataraj
mnatarajspu@gmail.com
1
P. O. Box 7, Miki-cho post office, Ikenobe 3011-2,
Kagawa-ken 761-0799, Japan
2
P.G. Department of Biosciences, Sardar Patel University,
Sardar Patel Maidan, Vadtal Rd., P.O. Box 39,
Vallabh Vidyanagar, Gujarat 388120, India
3
Resonance, Plot No - 21/5, Near Regional Science Centre,
Acharya Vihar, Bhubaneswar, Odisha 751013, India
123
J. For. Res. (2019) 30(3):745–754
https://doi.org/10.1007/s11676-018-0714-6
et al. 2017), and as a textile dye (Gulrajani et al. 2002). The
medicinal properties of P. santalinus have been extensively
reviewed elsewhere (Navada and Vittal 2014; Azamthulla
et al. 2015) and will not be covered in this review. However,
multiple uses (Table S2), ethnomedicinal uses (Table S3), and
phytochemistry (Table S4) have been provided as supple-
mentary tables to offer a more rounded appreciation of this
tree in the context of this review.
The texture and colour differentiate good quality from
poor quality trees, with ‘‘wavy grain wood texture with
intense red color’’ in the former and ‘‘straight grain wood
texture with light red color’’ in the latter (Prakash et al.
2006), and it is the superior quality of P. santalinus that
makes it popular in the furniture industry (Prakash et al.
2006; Arunkumar et al. 2011; Arunkumar and Joshi 2014;
Azamthulla et al. 2015). In Japan, P. santalinus is used to
make carvings and musical instruments, shamisen and koto
(Kukrety et al. 2013b; Arunkumar and Joshi 2014; Azam-
thulla et al. 2015; Ramabrahmam and Sujatha 2016), as well
as name seals or hankos. In Buddhism, P. santalinus is
considered to be a symbol of holiness, and is thus used for
carved statues, as a constituent of incense (Wu et al. 2011),
and for cremation (Ramakrishna 1962). In China, P. san-
talinus wood has a long history of use in furniture and other
valuable wood products (Berliner 1996; Kaner et al. 2013).
The export of P. santalinus from India to Europe started
in the 17th century, mainly for fabric dyeing (Vedavathy
2004). The Herbal Folklore Research Centre in Tirupati,
India, estimated that from 500 planted trees ha
-1
, at least
500 kg of heartwood per tree can be obtained after
25 years, thus 25 t ha
-1
of wood plantation (Vedavathy
2004). At 2004 prices of Rs. 75 kg
-1
, such a plantation
would yield a return of Rs. 177.5 lakhs ha
-1
(US$375,000 ha
-1
) (Vedavathy 2004). Current market
prices are, however, unknown to the authors, although
prices are likely to be high since natural P. santalinus
stands have been in decline as a result of this overex-
ploitation for commercial purposes, earning it an endan-
gered status since 1997 (IUCN 2018).
This review provides an overview of the reproductive
biology, seed germination and micropropagation of P.
santalinus as tools for its conservation and large-scale
propagation.
Basic flowering biology, and sexual and vegetative
reproduction
Pollination and seedset
The P. santalinus tree flowers in the dry season (Rao et al.
2001; Rao and Raju 2002). The flowers are papilionaceous,
bisexual, large and and yellow (Rao and Raju 2002).
Flowering is discontinuous, blooming at intervals of 2–5 d
(Rao et al. 2001). Flowers open at night and the primary
pollinators are Apis dorsata,A. cerana indica and A. florea
(Rao and Raju 2002). P. santalinus, which shows facultative
xenogamy, tends to eliminate growing fruits from self-polli-
nated flowers, i.e., there is large-scale abortion of flower buds,
flowers and fruit (Rao et al. 2001), and has very low fruit set
(-6%), 52% of which set seed (Rao and Raju 2002).
Seed germination
Traditional seed propagation of P. santalinus yields low
germination percentages due to a hard testa, poor viability,
and sensitivity to temperature (Kumar and Gopal 1975;
Dayanand and Lohidas 1988; Anuradha and Pullaiah 1998;
Naidu 2001a,b; Naidu and Rajendrudu 2001). Dried,
soaked and scarified P. santalinus pods resulted in 49%
germination (Kumarasinghe et al. 2003) although seed
germination in natural stands or under artificial propagation
is generally low (-30%) (Kumar and Gopal 1975; Day-
anand and Lohidas 1988; Kalimuthu and Lakshmanan
1995; Naidu 2001a,b;Naidu and Rajendrudu 2001).
Alternate wetting and drying every 48 h enhanced germi-
nation, reaching 73% (Vijayalakshmi and Renganayaki
2017). Seed germination, seedling height, and root collar
diameter were all significantly stimulated by fire (Kukrety
et al. 2013b). Presoaking P. santalinus pods with 500 mg/L
gibberellic acid for 24 h resulted in 66.7% seed germina-
tion, as well as improved plant growth and seedling sur-
vival relative to other treatments with tap water, luke warm
water, gibberellic acid, H
2
SO
4
or HCl (Patel et al. 2018).
Vegetative propagation
Vegetative propagation of P. santalinus by semi-hardwood
cuttings, cleft grafting, or air layering is not able to produce
stock numbers required for effective preservation or for
commercial purposes (Kedharnath et al. 1976;Kesava
Reddy and Srivasuki 1990). Relative to seed germination,
there are almost no studies on ex vitro vegetative propaga-
tion for red sanders. However, to provide elite germplasm
with desired traits, such as the wavy grain or phytochemicals
such as santalins, vegetative propagation under controlled
conditions is desirable, and in vitro propagation allows for
the production of true-to-type plants via micropropagation
such as axillary shoot multiplication or shoot tip culture at a
large scale, to continuously produce plantlets with uniform
characteristics. In tree biotechnology, such as for Indian
sandalwood (Teixeira da Silva et al. 2016b), in vitro prop-
agation also allows for the improvement of desired charac-
teristics such as pathogen resistance or improved wood
quality by genetic engineering. The next section assesses the
progress of micropropagation of P. santalinus.
746 J. A. Teixeira da Silva et al.
123
Micropropagation
Explants
The explant source (i.e., mother plant) and the procedure to
surface disinfect explants are important aspects underlying
the success of a tissue culture protocol (Leifert et al. 1994;
Teixeira da Silva et al. 2016c). Information about the
explants used for the in vitro propagation of P. santalinus,
as well as surface disinfection protocols, are summarised in
Table 1.P. santalinus seedlings derived from in vitro seed
germination have been a popular source of explants, while
in vitro germinated seedlings, shoot tips, cotyledons,
hypocotyls, mesocotyl and nodes have also served as
popular sources of explants for culture initiation since they
do not require surface disinfection (Lakshmi Sita et al.
1992; Anuradha and Pullaiah 1999a,b; Chaturani et al.
2005; Rajeswari and Paliwal 2008; Balaraju et al. 2011;
Vipranarayana et al. 2012; Warakagoda and Subasinghe
2013). In terms of ex vitro sources of explants, Prakash
et al. (2006) used young terminal shoot cuttings collected
from mature trees in winter as the explant; Ashrafee et al.
(2014) used leaf segments from 1 to 2 year old plants while
Sarita et al. (1988) used nodes and terminal cuttings.
Basal medium
The most commonly used and preferred basal medium for
in vitro studies on P. santalinus is Murashige and Skoog
(1962) (MS) medium (Table 2). Lakshmi Sita et al. (1992)
used Gamborg’s B
5
medium (Gamborg et al. 1968) with
2% sucrose and 0.8% agar to multiply axillary shoots from
shoot tips derived from seedlings germinated in vitro.
Chaturani et al. (2006) used Anderson medium (Anderson
1980) and Vitis medium (Chee and Pool 1987) to germinate
seed. Anuradha and Pullaiah (1999a) employed half-
strength B
5
medium supplemented with 0.05% activated
charcoal to germinate seeds in vitro then used B
5
medium
with 8.88 lM 6-benzyladenine (BA) for shoot tip culture.
In vitro propagation from predetermined meristems
Three predetermined meristems were employed in P.
santalinus tissue culture: shoot tips, cotyledonary nodes
and nodes from mature trees (Table 2). Shoot tips from
in vitro germinated seedlings were used by Lakshmi Sita
et al. (1992), Anuradha and Pullaiah (1999a), and Balaraju
et al. (2011) for shoot tip culture, with either BA as the
most effective cytokinin (Lakshmi Sita et al. 1992; Anu-
radha and Pullaiah 1999a) or a combination of BA and
thidiazuron (Balaraju et al. 2011). Cotyldenory nodes were
sucessfully applied for the in vitro propagation of P.
santalinus (Anuradha and Pullaiah 1999a; Arockiasamy
et al. 2000; Rajeswari and Paliwal 2008; Warakagoda and
Subasinghe 2013). BA, alone or combined with other
cytokinins or auxins, has frequently been utilized for the
micropropagation of P. santalinus (Table 2). Prakash et al.
(2006) cultured nodes of mature trees directly on filter
paper bridges employing liquid MS medium containing
1.16–9.30 lM kinetin or 1.11–8.88 lM BA, as well as an
antioxidant, observing that 4.44 lM BA was optimum for
bud break and shoot multiplication.
In vitro propagation (callogenesis, regeneration
and somatic embryogenesis)
Leaf, cotyledon, root, internode and nodal segments (pre-
sumably with axillary buds) from in vitro P. santalinus
seedlings formed callus, but shoot regeneration was not
reported (Chaturani et al. 2005). Callus was induced from
leaves and internodes of P. santalinus by Ashrafee et al.
(2014) solely to assess antibiotic activity against Aero-
monas and Pseudomonas but regeneration was not asses-
sed. Details of effective plant growth regulator
concentrations and combinations, medium composition,
and explant type, as well as their effects on morphogenesis
are presented in Table 2.
Rooting and acclimatization
Sucessful roooting of in vitro-raised plants followed by
effective acclimatization and successful transfer of in vitro-
propagated plants to field conditions is the final objective
of any micropopagation protocol and care is needed to
avoid hyperhydricity in in vitro-raised plants, which tend to
display poor rooting efficiency (Ruffoni and Savona 2013;
Teixeira da Silva et al. 2017b). Rooting and acclimatization
protocols for in vitro-raised shoots of P. santalinus are
summarized in Table 2. Only a few studies have quantified
the survival of micropropagated plants (Lakshmi Sita et al.
1992; Prakash et al. 2006; Rajeswari and Paliwal 2008;
Balaraju et al. 2011; Warakagoda and Subasinghe 2013).
Among the 12 reports on P. santalinus tissue culture,
in vitro rooting employed full-strength, half-strength and
quarter-strength MS medium (Table 2). According to
Arockiasamy et al. (2000), quarter-strength MS medium
supplemented with 5.71 lM IAA was effective for 76.2%
rooting of shoots derived from cotyledenory nodes, but
acclimatization and survival of plantlets were not reported.
Vipranarayana et al. (2012) applied a pulse treatment of
7.34 lM IBA in half-strength MS but details about survival
were not reported. Rajeswari and Paliwal (2008) achieved
85% plantlet survival ex vitro after a pulse treatment of
5lM IAA and 1 lM IBA for 25 d. In contrast, Warak-
agoda and Subasinghe (2013) showed limited success (46%
Red sandalwood (Pterocarpus santalinus L. f.): biology, importance, propagation and…747
123
Table 1 Explant source, size and surface sterilization procedures for preparation of tissue culture studies of Pterocarpus santalinus (chrono-
logical listing)
Explant source Explant type, size and density; culture
vessel
Surface sterilization and preparation References
Seeds (soaked and dried for 15 d) ?
seedlings. Age and source of mother
plant NR
Size of shoot tips (15-d-old seedling)
NR. 5–8 mm shoot tips and nodes
from in vitro grown shoots. Test tubes
(15 mL/tube)
Shoot tips: RTW (duration NR) ?soap
(soap name, duration of treatment and
concentration NR) ?0.1% HgCl2
15 min ?3-4X SDW
Lakshmi Sita
et al. (1992)
Seeds from the wild ?seedlings. Age
of mother plant NR
Roots, hypocotyls, mesocotyls,
cotyledons, shoot tips, nodes, leaves,
internodes (size NR for all explants)
from 15-d old seedlings 6–7 cm tall
with 3–4 nodes. Test tubes (1
explant/tube)
Pods: 50% HCl ?50% EtOH 2–3 h ?
TRW ?dried for 2 d ?pods opened
and seeds sown directly in vitro
Anuradha and
Pullaiah
(1999a)
Seeds from the wild ?seedlings. Age
of mother plant NR
Hypocotyls (1 cm), epicotyls (1 cm),
cotyledons (1.5 cm), shoot tips
(0.5 cm), internodes (0.5 cm), axillary
nodes (0.5 cm) from 20-d old
seedlings. Test tubes (1 explant/tube)
Seeds from dried pods: 70% alcohol
1 min ?0.1% HgCl2 ?0.1% sodium
dodecyl sulfate 10 min ?5X DDW
?SDW 24 h ?SDW replaced every
8h
Arockiasamy
et al. (2000)
Pods (\3to[5 cm) including wing.
Age of mother plant NR
Seeds from pods of various sizes. Pods
stored at 28 ±5C for 1–4 weeks.
Culture vessel NR
Seeds: 5% Teepol (duration NR) ?
RTW 2 h ?0.1% HgCl2 ?2 drops
Tween-20 (5–25 min) ?3X SDW
10 min
Chaturani et al.
(2006)
10-y-old tree, sampled in Nov.-Jan. Mature nodes from terminal shoots
(7–8 cm long). 25 9150 mL test
tubes (1 explant/tube)
Shoots: 1% Teepol 30 min ?cut into
nodal segments 2–3 cm long ?70%
EtOH 2 min ?0.1% HgCl2 ?0.1%
Tween-20 7 min ?5X SDW
Prakash et al.
(2006)
Mature pods and nodes (forest and
campus culture)
Pods scarified in boiling water (5 min)
or 5% H2SO4 (10 min). Culture vessel
NR
Seeds and nodes: RTW 30 min ?testa
removed ?2% Bavistin (15 min for
nodes, 30 min for seeds) ?70%
EtOH 2 min ?0.1% HgCl2 (15 min
for nodes, 12 min for seeds) ?4-5X
SDW
Padmalatha
and Prasad
(2007,2008)
Seeds ?seedlings. Age and source of
mother plant NR
Seedling-derived cotyledonary nodes
(1.5 cm long), nodal segments (1 cm
long). Test tubes (1 explant/tube)
Explants from 30-d-old seedlings: RTW
1h?0.025% Tween-20 10 min ?
3X DW ?0.1% HgCl2 10 min ?3X
SDW
Rajeswari and
Paliwal
(2008)
Seeds from the wild ?seedlings Shoot tips of 20-d-old in vivo seedlings.
50-mL Borosil test tubes (1–2
explants/tube)
Peeled seeds: 1% Bavistin (fungicide)
10 min ?wash with H2O ?
50–300 ppm GA3 24 h. Apical
meristem explants: RTW 10 min ?
DW ?some drops Tween-20 5 min
?SDW 2-3X ?1% Bavistin 5 min
?SDW ?70% EtOH 30 s ?SDW
2-3X ?0.1% HgCl2 3 min ?4X
SDW
Balaraju et al.
(2011)
In vitro seedlings (age NR) Nodal segments; one explant per test
tube (150 mm 925 mm)
Seeds: RTW 30–40 min ?5% Teepol-
B-300 (wetting agent) stirring 15 min
?1% Bavistin Carbandazim
(fungicide) 10 min ?DW 30 min ?
70% EtOH 30 s ?0.05% HgCl2
5–10 min ?4X SDW
Vipranarayana
et al. (2012)
748 J. A. Teixeira da Silva et al.
123
of plantlets rooted) ex vitro with 49,000 lM IBA, possibly
because of the excessively high concentration of this auxin.
Variability in quality and quality control
There is a problem with the adulteration and falsification of
plant material in the P. santalinus market. The heartwood
of Adenanthera pavonina Willd. (Mimosaceae), known as
‘Ranjana’ and ‘Raktakambal’ in West Bengal and ‘Bari
Gumchi’ in the northern parts of India, is often sold as a
fake substitute for P. santalinus, while artificially colored
wood shavings and the sawdust of some other trees are also
sold on the market as cheap substitutes (Botanical Survey
of India 2012). In China, the manufacture of furniture
utilizes Dalbergia louvelii R. Vig. (violet rosewood) as a
substitute for P. santalinus since both plants have a very
similar appearance and anatomical characteristics, and
cheaper D. louvelii is often illegally used to impersonate
the valuable P. santalinus (Zhang et al. 2014). Zhang et al.
(2014) used conventional infrared spectroscopy (FT-IR),
second derivative infrared (SD-IR) spectroscopy and two-
dimensional correlation infrared (2DCOS-IR) spectroscopy
to differentiate furniture made of P. santalinus wood from
furniture made from D. louvelii. They observed that P.
santalinus wood had a higher holocellulose content than D.
louvelii wood while D. louvelii had more NaOH- and
benzyl-alcohol-based extracts than P. santalinus.
The size and age of trees affects the heartwood content
and wood density of P. santalinus (Suresh et al. 2017).
Woody anatomy such as grain waviness can be used to
delimit and identify P. santalinus (Rawat and Uniyal 1996;
Gasson and MacLachlan 2010). The Botanical Survey of
India (2012) used various anatomical methods such as
maceration, scanning electron microscopy, exo- and
endomorphic features, and fluorescence analysis to cor-
rectly identify P. santalinus wood samples.
Molecular markers are regularly utilized to measure the
degree of genetic variation within natural or breeding
populations, and have been extensively used in Indian
sandalwood research (Teixeira da Silva et al. 2017a). In P.
santalinus, RAPD (random amplified polymorphic DNA)-
based marker analysis was used to detect variations in
micropropagated plants raised from shoot tips, verifying
that in fact no variation existed (Balaraju et al. 2011).
RAPD was also used by Usha et al. (2013) to detect vari-
ation among nursery-grown plants. Variation in genetic
distance among natural accessions, detected by RAPD
markers, reflected a high level of DNA polymorphism due
to outcrossing (Padmalatha and Prasad 2007; Usha et al.
2013). Jhansi Rani and Usha (2013) developed a sequence
characterized amplified region (SCAR) marker to differ-
entiate wavy from straight-grained plants at the seedling
stage. Jyothi et al. (2014) reported differences in the
quantity of genomic DNA in samples collected from dif-
ferent locations in Andhra Pradesh, India.
Therefore, quality control, as assessed by anatomical or
chemical methods, is essential to verify the originality of P.
santalinus wood while molecular methods serve to confirm
genetic stability.
Table 1 continued
Explant source Explant type, size and density; culture
vessel
Surface sterilization and preparation References
1. Seeds from green-brown pods from
25-y-old trees
2. Age of mother plants in greenhouse
NR. Greenhouse conditions NR.
Terminal bud removed and sprayed
with 10 mg/l BA at 2-w intervals. 70%
thiophanate methyl (topsin) sprayed at
100 mg/l 24 h before collecting
explants. Plants treated with 200 mg/l
Albert’s solution (liquid fertilizer) at
2-w intervals
1. Mesocotyl segments, cotyledonary
nodal segments, shoot tips, from 20-d-
old in vitro germinated seedlings and
seedlings
2. Immature and semi-hard shoot
segments
Culture vessel and other conditions for 1
and 2 NR
Seeds: 10% Clorox
(fungicide) 20 min
?70% EtOH 2 min ?rinse NR
Shoot segments: 5% Teepol 5 min ?
RTW 30 min ?0.3% topsin solution
1h?2X SDW ?Clorox
?2 drops
Tween-20 (10, 15, 20% for 10, 15,
20 min each) ?70% EtOH 2 min ?
2X DW. Whole process repeated twice
Warakagoda
and
Subasinghe
(2013)
1–3-y-old trees Leaves and internodes. Size and density
NR; test tubes
Leaves: wash in DW ?70% EtOH 30 s
?0.1% HgCl2 3 min. Internodes:
70% EtOH 2 min ?0.1% HgCl2 ?
2–3 drops Tween-20 7 min. No rinses
described for both explants
Ashrafee et al.
(2014)
dday(s), DW distilled water, DDW double distilled water, EtOH ethyl alcohol (ethanol), GA
3
gibberellic acid, HgCl
2
mercury chloride, IZE
immature zygotic embryo, NaOCl sodium hypochlorite, NR not reported in the study, RTW running tap water, ssecond(s), SDW sterilized (by
autoclaving) distilled water, SW sterilized water, yyear(s)
Red sandalwood (Pterocarpus santalinus L. f.): biology, importance, propagation and…749
123
Table 2 In vitro conditions for tissue culture studies of Pterocarpus santalinus (chronological listing)
Culture medium, PGRs,
additives, subcultures
Culture conditions
a
Experimental outcome, maximum productivity, acclimatization
and variation
References
B
5
?0.88 lM or 4.44 lM
BA ?0.46 or 4.6 lM Kin
(SIM). MS ?
5.71–28.59 lM IAA or
4.9–24.42 lM IBA
(RIM). pH 5.6–5.8. 2%
sucrose. 0.8% agar.
Subculture every 4–5 w
16-h PP. CWFT.
1200 lx. 25 C.
RH NR
Shoot tips from in vitro seedlings produced 4–5 cm shoots with
4–5 nodes. Shoot tips from in vitro grown shoots produced up to
8 shoots 3–5 cm long on B
5
?4.44 lMBA?4.65 lM Kin
within 4–6 w. Nodal explants produced 1 shoot/explant. 80%
rooting on IAA vs. 30–40% on IBA in RIM. 5.71–11.43 lM
IAA produced adventitious roots but 28.59 lM IAA produced a
thick tap root. Acclimatization in sterilized soil ?sand (1:1)
with 50% survival. 60% survival when kept in liquid RIM for 2
w then transferred to test tubes with only water for 1 w and the
finally to plastic covered pots
Lakshmi Sita et al. (1992)
B
5
?0.05% AC ?
0.44 lM BA (SG). B
5
?
8.88 lM BA (SIM). MS
?0.57 lM IAA ?
0.49 lM IBA ?0.53 lM
NAA (RIM). pH 5.7–5.8.
3% sucrose. Gelling agent
NR
NR 40–70% germination in 24 h. Only shoot tips, nodes and
mesocotyls formed shoot buds and multiple shoots; the five other
explants induced callus. Mesocotyls formed maximum
shoots/explant (7–8). MS and WPM not as effective as B
5
as
SIM basal medium. Acclimatization claimed in sand ?soil, but
not quantified
Anuradha and Pullaiah (1999a)
MS ?2% sucrose ?0.6%
agar (SG). MS ?
0.53 lM NAA ?
4.44 lMBA?4.65 lM
Kin (SIM). MS ?
5.71 lM IAA (RIM).
Carbon source, gelling
agent, pH NR
16-h PP. Light
source NR.
1200 lx. 26 C.
RH NR
10.4 shoots/cotyledon on SIM. No shoots formed from epicotyls,
hypocotyls or internodes. 76.2% of cultures rooted.
Acclimatization claimed in sterilized garden soil ?sand (1:1)
and watered with RIM for 1 w, but not quantified
Arockiasamy et al. (2000)
MS, WPM, Anderson or
Vitis basal medium ?AC
conc. NR or without AC
(SG). pH NR. 3% sucrose.
08% agar
12-h PP. Light
source NR. 23 ±
2C. RH NR
90% germination after 15 min exposure to 0.1% HgCl
2.
\3cm
pods were either seedless or with fragile seeds. About 95% of
seeds from pods [5 cm in size germinated. No correlation
between size and germination period. 96% germination in pods
stored for 1 w at 28 ±5C. Storage period and browning were
inversely proportional to germination efficiency. Rapid (within 6
d) germination (92%) with 10 mm hypocotyls was possible from
seeds cultured on Anderson medium without AC.
Chaturani et al. (2006)
Liquid MS ?4.4 lMBA?
2.2 lM TDZ (SIM,
SMM) with 6-w
subcultures on paper
bridges. MS ?4.9 lM
IBA (RIM). pH 5.8. 3%
sucrose. 0.8% agar (RIM
only)
16-h PP. CWFT. 50
lEm
-2
s
-1
.25±
2C. 65% RH
Subculture on paper bridges improved nodal explant survival more
than all antioxidants tested but 80% of cultures showed
browning. 74–75% of nodes formed axillary shoots. An 8.3-fold
increase in shoots by the 6th subculture. 70% survival after
acclimatization in autoclaved soil ?FYM (4:1) after 5 months
Prakash et al. (2006)
750 J. A. Teixeira da Silva et al.
123
Table 2 continued
Culture medium, PGRs,
additives, subcultures
Culture conditions
a
Experimental outcome, maximum productivity, acclimatization
and variation
References
MS ?13.32 lM BA (SIM,
nodes). MS ?4.44 lM
BA ?9.30 lM Kin (SIM,
seeds). MS ?4.44 lM
BA (SMM, nodes, seeds).
Auxin-free MS ?0.25%
phytagel (RIM). pH NR.
3% sucrose. 0.6% agar
16-h PP. CWFT.
83.6 lEm
-2
s
-1
.25
±2C. 60–70% RH
17 shoots/seed explant on SIM, then SMM, with 90% explant
response. Rooting data NR. Low (20%) survival of acclimatized
plantlets in Soilrite
?manure ?sand (1:1:1)
Padmalatha and Prasad (2008)
MS ?2.5 lMBA?2lM
2iP (SIM, SMM). Dip in
5lM IAA ?1lM IBA
(ex vitro RIM). pH NR.
3% sucrose. 0.8%
Bactoagar
16-h PP. CWFT.
60 lmol m
-2
s
-1
.
24 ±2C. RH NR
Max. of 4/4 shoots/cotyledonary node in 2nd subculture in 95% of
cotyledonary nodes. 82.5% of shoots induced roots. 95%
survival of acclimatized plantlets in coarse sand ?clay ?FYM
(1:1:1). Tissue-cultured plants showed better morphological
performance than seedlings
Rajeswari and Paliwal (2008)
MS ?1 mg/l BA ?
0.45 lM TDZ (SIM).
Subculture every 4 w. MS
?2.22 lMBA?
0.28 lMGA
3
(shoot
elongation). MS ?
0.49 lM IBA (RIM)
using 3–4 cm long shoots
with 4–5 leaves. After 4
w, transfer to PGR-free
MS (root elongation). pH
5.8. 2% sucrose. 0.8%
agar
16-h PP. CWFT.
35–50 lmol m
-2
s
-1
.22±1C. RH
NR
% SG NR. 83% of shoot tips formed new shoots, with 11
buds/explant after 45 d. 60% of shoots rooted. 73.3% survival of
acclimatized plantlets in organic manure and garden soil ?sand
(1:1) under in vitro culture conditions. RAPD used to confirm
lack of variation
Balaraju et al. (2011)
MS ?2lMGA
3
(SG). MS
?1 mg/l BA ?0.5 mg/l
NAA (SIM). Pulse in
1.5 g/l IBA ?MS
(RIM). pH 5.8. 3%
sucrose. 0.8% agar
16-h PP. CWFT.
50 lmol m
-2
s
-1
.
25 ±2C. 65% RH
85% of adventitious shoots elongated. 8.8 shoots/shoot tip. 85%
rooting after 4 w in soil ?manure (1:1) (survival NR)
Vipranarayana et al. (2012)
MS, WPM or B
5
?
4–12 lMBA?
0.5–2 lM NAA (SIM).
25–2500 mg/l IBA pulse
treatment 12 h ?MS
?0.5 lM IBA (RIM). pH
5.8. 3% sucrose. 0.01%
myo-inositol. Gelling
agent NR
16-h PP. CWFT.
1220 lx. 23 ±2C.
60% RH
80% survival from immature cuttings when surface sterilized with
15% Clorox
for 10 min. 0.1% AC with WPM was best
interaction. No significant difference in interaction between
media and explant type. Maximum number of shoot buds
(-4.95)/cotyledonary nodal explant on B
5
medium
supplemented with 8 lM BA and 2 lM NAA. Longest roots in
25 mg/L pulse treatment. Ex vitro rooting using 1000 mg/L IBA
produced 40% rooting. Acclimatization performed in sand ?
coir dust (1:1) was 80% when kept in humid conditions and weak
light for the first 4 w then for 6 w in greenhouse
Warakagoda and Subasinghe (2013)
Red sandalwood (Pterocarpus santalinus L. f.): biology, importance, propagation and…751
123
Conclusions and future perspectives
This review highlights key advances in the tissue culture-
based biotechnology of economically important Pterocar-
pus santalinus. To date, effective protocols for seed surface
disinfection and in vitro germination exist. There are also
effective protocols for direct shoot regeneration from a
range of explants or through callus induction. In most
cases, explants are derived from seeds or seedlings which
are not suitable for clonal propagation (Table 1). There-
fore, a clonal method should be developed from vegetative
tissues of elite germplasm. Rooting and survival of
micropropagated plants remain a major limitation to the
success of P. santalinus tissue culture and should be opti-
mized in the future, for example by using CO
2
enrichment
and vessels that allow for maximized aeration without
impacting relative humidity levels within the culture vessel
(Teixeira da Silva et al. 2005). The ability to stably pro-
duce units that allow for germplasm conservation would
then stimulate the need for cryoconservation (Teixeira da
Silva and Engelmann 2017; Bi et al. 2017), including
through the application of synthetic seeds (Sharma et al.
2013). Analytic hierarchy, which is a multicriteria deci-
sion-making tool, is valuable for incorporating the per-
ceptions of stakeholders when planning the conservation
and restoration of a P. santalinus population (Kukrety et al.
2013a,c). The micropropagation and biotechnology of
another commercially important tree in this genus, P.
marsupium (Indian kino tree), have recently been reviewed
(Teixeira da Silva et al. 2018).
Acknowledgements The authors thank Dr. Emilia Caboni (Agri-
cultural Research Council (CRA), Fruit Tree Research Centre, Rome,
Italy), Dr. Randall Niedz (U.S. Department of Agriculture, Agricul-
tural Research Service, U.S. Horticultural Research Laboratory, FL,
USA) and Dr. Ivana Gribaudo (Istituto Protezione Sostenibile delle
Piante—CNR, Grugliasco, Italy) for ideas, comments and suggested
improvements to an early version of the manuscript. The authors also
thank Prof. M.N.V. Prasad (Department of Plant Sciences, University
of Hyderabad, India) for some suggestions on a later version of the
manuscript.
Open Access This article is distributed under the terms of the
Creative Commons Attribution 4.0 International License (http://crea
tivecommons.org/licenses/by/4.0/), which permits unrestricted use,
distribution, and reproduction in any medium, provided you give
appropriate credit to the original author(s) and the source, provide a
link to the Creative Commons license, and indicate if changes were
made.
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Table 2 continued
Culture medium, PGRs,
additives, subcultures
Culture conditions
a
Experimental outcome, maximum productivity, acclimatization
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References
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