reported to be far and wide. Further research work demonstrated that Sandalwood
exhibits considerable variability for different morphological traits. Variability was
documented for the bark colour, texture, thickness and rust coloured bark being
associated with fast growth (Kulkarni and Srimathi 1982) Seeds showed polymorphic characters in size, shape, germination and vigour. (Nagaveni and
Anathapadmanabha 1986; Veerendra and Sarma 1990; Ramalakshmi and
Rangaswamy 1998; Annapurna et al. 2005) and six types of leaves—ovate (common), lanceolate (12 %), elliptic, linear, small and big which were being discernible
at juvenile stage (Kulkarni and Srimathi 1982; Bagchi and Veerendra 1985). Apart
from the variability for the morphological traits, various studies using molecular
markers have revealed that there is considerable genetic diversity in Sandalwood
population (Angadi et al. 2003; Shashidhara et al. 2003; Suma and Balasundaran
2003, 2004; Nageshwar Rao et al. 2007; Jones 2008; Azeez et al. 2009).
3 Studies on Heartwood and Oil Content
Considering the importance and value of Sandalwood, two traits that play significant role are heartwood and oil content. Studies have been carried out by various
authors and initially most of them being on the basis of field observations/opinions
and very few of them have been supported with scientific data. Cameron (1894)
suggested that Sandalwood tree attains commercial maturity at 27–30 years. Rama
Rao (1904) found that there was variation in heartwood content between and within
different girth classes of trees. Singh (1915) in his observation on 40 trees was of
the view that elevation, age or locality has any definite relation with the oil quality.
Even in the Fifth Silviculture Conference held at Dehradun in 1941, Mitchell
stressed that it would take a long time to determine factors ideal for formation of
heartwood and increasing the oil content and merits investigation. Bhatnagar (1965)
reported that Sandalwood trees reach full maturity at an age of 50–80 years or more
and a tree may reach physiological maturity without forming any heartwood. Even
in the First All India Sandal Seminar held in Bangalore in 1977 and the subsequent
Second All India Sandal Seminar that was convened highlighted the fact that
selection of genotypes having higher heartwood content and research on heartwood
formation must be given a priority. Srimathi and Kulkarni (1980) carried out an
interesting study to understand the variation for heartwood content among different
trees (n = 50) having similar diameter of 11 cm in the Forest Research Laboratory
Campus. It was found that the coefficient of variation value was as high as 41.7 %
for heartwood content. They opined that there is no fixed year when the heartwood
starts forming and mentioned that it can start as early as 5–6 years in some trees and
as late as over 15 years. Similarly, Jayappa et al. (1981) collected Sandalwood
samples from different locations and found variability in Sandalwood oil for α and β
Santalol content. Even though most of the studies revealed substantial insights
about heartwood and oil, the major inherent flaw in most of these studies were that
the samples were collected from the trees in which age was not known. The effect
380
A.N. Arunkumar et al.
exhibits considerable variability for different morphological traits. Variability was
documented for the bark colour, texture, thickness and rust coloured bark being
associated with fast growth (Kulkarni and Srimathi 1982) Seeds showed polymorphic characters in size, shape, germination and vigour. (Nagaveni and
Anathapadmanabha 1986; Veerendra and Sarma 1990; Ramalakshmi and
Rangaswamy 1998; Annapurna et al. 2005) and six types of leaves—ovate (common), lanceolate (12 %), elliptic, linear, small and big which were being discernible
at juvenile stage (Kulkarni and Srimathi 1982; Bagchi and Veerendra 1985). Apart
from the variability for the morphological traits, various studies using molecular
markers have revealed that there is considerable genetic diversity in Sandalwood
population (Angadi et al. 2003; Shashidhara et al. 2003; Suma and Balasundaran
2003, 2004; Nageshwar Rao et al. 2007; Jones 2008; Azeez et al. 2009).
3 Studies on Heartwood and Oil Content
Considering the importance and value of Sandalwood, two traits that play significant role are heartwood and oil content. Studies have been carried out by various
authors and initially most of them being on the basis of field observations/opinions
and very few of them have been supported with scientific data. Cameron (1894)
suggested that Sandalwood tree attains commercial maturity at 27–30 years. Rama
Rao (1904) found that there was variation in heartwood content between and within
different girth classes of trees. Singh (1915) in his observation on 40 trees was of
the view that elevation, age or locality has any definite relation with the oil quality.
Even in the Fifth Silviculture Conference held at Dehradun in 1941, Mitchell
stressed that it would take a long time to determine factors ideal for formation of
heartwood and increasing the oil content and merits investigation. Bhatnagar (1965)
reported that Sandalwood trees reach full maturity at an age of 50–80 years or more
and a tree may reach physiological maturity without forming any heartwood. Even
in the First All India Sandal Seminar held in Bangalore in 1977 and the subsequent
Second All India Sandal Seminar that was convened highlighted the fact that
selection of genotypes having higher heartwood content and research on heartwood
formation must be given a priority. Srimathi and Kulkarni (1980) carried out an
interesting study to understand the variation for heartwood content among different
trees (n = 50) having similar diameter of 11 cm in the Forest Research Laboratory
Campus. It was found that the coefficient of variation value was as high as 41.7 %
for heartwood content. They opined that there is no fixed year when the heartwood
starts forming and mentioned that it can start as early as 5–6 years in some trees and
as late as over 15 years. Similarly, Jayappa et al. (1981) collected Sandalwood
samples from different locations and found variability in Sandalwood oil for α and β
Santalol content. Even though most of the studies revealed substantial insights
about heartwood and oil, the major inherent flaw in most of these studies were that
the samples were collected from the trees in which age was not known. The effect
380
A.N. Arunkumar et al.