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Molecular Plant Breeding 2012, Vol.3, No.2, 11
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21
each of the two species (Table 4). This suggested
considerable gene flow between genotypes of the
exotic and indigenous collections of the two jute
species, which also can be observed in the pattern of
UNJ dendrograms, PCA plots and population structure
in the two species separately. This could be a
consequence of exchange of germplasm between
geographical areas for cultivation.
The estimates of genetic diversity and occurrence of
private alleles also suggested that within
C. capsularis
,
the indigenous genotypes were more diverse than
the exotic genotypes which again indicated the
Indo-Burma region to be the primary centre of
diversity for
C. capsularis
as reported earlier (Basu
et al., 2004). However in
C. olitorius
, few genetic
diversity parameters were slightly higher in the exotic
collection than in the indigenous collection (Table 5)
indicating that the exotic genotypes harbour a
considerable amount of the genetic diversity. The
exotic genotypes of
C. olitorius
also possessed higher
number of private alleles than the genotypes of
C.
capsularis
indicating that genetic differentiation
occurred due to mutation of alleles in a particular
geographic location (Table 5). The SSR loci reported
in the present study detecting private alleles (>6%
frequency, Table 7) in indigenous and exotic collections
of genotypes might be used to discriminate the
indigenous and exotic genotypes of both the species.
2.4 Genetic distance and jute improvement
Based on the range of pair-wise genetic distances
(estimated by GenAlEx, as discussed in Material and
methods) in
C. capsularis
, four pair of genotypes,
namely CIM 021(India)-CIJ 013 (Thailand), CIJ 013
(Thailand)-CIM 009 (India), CIM 021 (India)-CEX
070 (Brazil) and CIM 021 (India)-CIJ047 (Thailand)
showed maximum genetic distance (range of GD=20.1
to 20.3). Similarly in
C. olitorius
three pairs of
genotypes, namely OIJ 245 (Nepal)-OIM 020 (India),
OIJ 245 (Nepal)-JRO 8432 (India) and OIJ 210
(Nepal)-OIJ 228 (Nepal) showed maximum genetic
distance (GD = 21.91each). These pairs of most diverse
genotypes in the two species can be involved in
hybridization program aimed at improvement of the
two cultivated yet neglected jute species.
The present study reports SSR diversity in jute as a
whole and also in two different cultivated species
separately. This kind of large scale effort is performed
for the first time in jute, where more than 100
polymorphic SSRs, species specific loci/alleles were
identified. The diverse genotypes identified by these
SSR markers can be used in future hybridization
programs. These polymorphic SSR markers along
with AFLP markers (Das et al., 2011) can also be
utilized for construction of framework linkage maps
for two jute species for studies involving QTL
analysis and detection of marker-trait associations.
The knowledge of SSR loci that are specific for a
country can further be exploited in varietal development.
Divergent genotypes detected in this study should be
useful for marker-assisted selection (MAS) involving
fibre yield contributing and fibre quality traits (lignin
content/fibre fineness), leading to the improvement in
jute productivity and quality.
3 Materials and Methods
3.1 Plant materials
Out of a large collection (~2600) of jute genotypes
maintained at Central Research Institute for Jute and
Allied Fibres (CRIJAF), Barrackpore, India, a set of
292 diverse jute genotypes belonging to the two
cultivated jute species, namely
C. capsularis
(152
genotypes) and
C. olitorius
(140 genotypes), was used
in the present study. These 292 jute genotypes included
accessions of both indigenous and exotic origin. The
indigenous genotypes included improved lines and
varieties, while exotic genotypes belonged to 12
different countries namely Nepal, Sri Lanka, China,
Burma, Thailand, Indonesia, Japan, Australia, Brazil,
Kenya, Sudan and Tanzania (for details see Supple-
mentary Table 2 and Figure 6).
3.2 DNA Isolation
Seeds of 292 genotypes were allowed to germinate in
Petri plates in our laboratory. The DNA was extracted
from 5
-
7 day old seedlings following modified CTAB
method (Saghai-Maroof et al., 1984) and was purified
by RNaseA treatment, followed by phenol: chloroform
extraction. The purified DNA was quantified with a
UV-spectrophotometer (model UV5704SS, Electronic
Corporation of India Limited, Hyderabad, India).