characterization of genetic diversity in jatropha...
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Indian Journal of Biotechnology
Vol 11, January 2012, pp 54-61
Characterization of genetic diversity in Jatropha curcas L. germplasm
using RAPD and ISSR markers
Varsha Khurana-Kaul1, Sumita Kachhwaha
1 and S L Kothari
1,2*
1Department of Botany and 2Centre for Converging Technologies (CCT), University of Rajasthan, Jaipur 302 004, India
Received 26 July 2010; revised 22 May 2011; accepted 18 July 2011
Jatropha curcas L. is a rapidly emerging biofuel crop attracting a lot of interest, triggering large investments and rapid
expansion of cultivation areas. In the present investigation, the genetic relationships of 29 J. curcas accessions were
assessed based on randomly amplified polymorphic DNA (RAPD) and inter simple sequence repeat (ISSR) analyses. A total
of 72 polymorphic primers (47 RAPD and 25 ISSR) were used. Amplification of genomic DNA of the 29 genotypes, using
RAPD analysis, yielded 552 fragments that could be scored, of which 334 were polymorphic with an average of 7.1
polymorphic fragments per primer. Number of amplified fragments varied from 2 to 23 and ranged in size from 100-3,500
bp. The 25 polymorphic ISSR primers used in the study produced 336 bands across 29 genotypes, of which 201 were
polymorphic. The number of amplified bands varied from 7 to 20 with a size range of 100-3,500 bp. Molecular
polymorphism was 60.5 and 59.8% with RAPD and ISSR markers, respectively. Mantel test between the two Jaccard’s
similarity matrices gave r=0.8623, showing good fit correlation between RAPD and ISSR based similarities. Clustering of
genotypes within groups remained more or less similar in ISSR and combined data of RAPD and ISSR.
Keywords: Genetic diversity, ISSR, Jatropha curcas, microsatellites, polymorphism, RAPD
Introduction
Bio-diesel is becoming popular as an alternative to
diesel on account of high demand, necessary policy
support and technological feasibility. India consumes
approximately 40 million tonnes of diesel annually
and has to import most of it1. Therefore, any
alternative to diesel becomes national priority.
Recently, government of India launched “National
Mission on Bio-diesel” with a view to find a cheap
and renewable liquid fuel based crop. Among the
potential non-edible oil yielding crops, Jatropha
curcas (physic nut) (Family: Euphorbiaceae) has
received the greatest attention lately as a promising
biofuel plant in tropical and sub-tropical countries2.
Jatropha can grow in poor soils with low rainfall and
its oil can be substituted with diesel without any
alteration in the existing automobile engines3. These
properties of the plant have fuelled intense research
on this crop in recent years.
In spite of numerous favourable attributes, the full
potential of the crop has not been realized due to lack
of planned breeding programmes for the creation of
new and improved varieties4. Once genetically
distinct varieties have been identified, these will serve
as a useful resource for cultivation under different
climates and development of new varieties through
breeding. It has been reported
that variability of
J. curcas in central India is mainly limited to seed
source variation in morphology, germination and
seedling growth5. Divergence in seed oil traits of
Jatropha has been reported from a limited number of
locally collected accessions6.
Molecular markers have been used to monitor DNA
sequence variation in and among the species and
create new sources of genetic variation by introducing
new and favourable traits from landraces and related
species. They are reliable indicators of genetic
diversity because they are neutral to environmental
influence and reveal differences at the whole genome
level10
. Among the various molecular markers
employed to assess diversity, PCR based markers,
such as, RAPD11
and ISSR12
, are being popular as
their application does not need any prior sequence
information. On the other hand, microsatellites or
simple sequence repeat (SSR) are the markers of
choice for breeding applications13
. Each of these
methods has been widely used to identify and
determine relationship at species and cultivar
levels14-17
. In Jatropha sp., analyses of genetic
diversity have been carried out using RAPDs and
ISSRs alone or in combination18-20
.
__________
*Author for correspondence:
Tel & Fax: +91-141-2703439
E-mail: [email protected]
KHURANA-KAUL et al.: GENETIC DIVERSITY IN J. CURCAS L.
55
The objective of the present study was to investigate
genetic variation among different genotypes of J.
curcas using RAPD and ISSR markers. This would act
as initial step towards selection and breeding of
superior genotypes including those having high oil
content and resistance to pests.
Materials and Methods
Plant Material and DNA Extraction
A representative set of 29 accessions of J. curcas
were collected from different regions of Rajasthan in
the year 2008 (Table 1). Total genomic DNA was
extracted from young leaves following the standard
CTAB method21
with minor modifications. Leaves
(5 g) were ground in liquid nitrogen, then
homogenized in 25 mL of extraction buffer
(2% CTAB, 20 mM EDTA, 2% PVP, 1.4 M NaCl,
100 mM Tris-HCl pH 8.0 and 1% β-mercaptoethanol)
and incubated at 65°C for 1 h. The supernatant was
treated with RNAase A, incubated at 37°C for 30 min
and extracted twice with chloroform:isoamylalcohol
(24:1 v/v). The DNA was pelleted with chilled
Table 1—Details of J. curcas germplasm collected from different locations in Rajasthan, India
No. Acc. code Location Latitude and longitude Collection site
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
U1
U2
U3
U4
U5
U6
U7
U8
U10
U11
B1
B2
B3
B4
B5
S1
A1
A2
C1
C2
C3
C4
D1
D2
D3
R1
R2
R3
U9
Bhuwana, Udaipur
Sisarma, Udaipur
Choti Undri, Udaipur
Daken Kota, Udaipur
Jhadol, Udaipur
Jhadol, Udaipur
Gogunda, Udaipur
Saira, Udaipur
Salumbar, Udaipur
Bhamrasiya, Udaipur
Bhilwara
Bhilwara
Bhilwara
Bhilwara
Bhilwara
Pindwara, Sirohi
Lasara, Banswara
Lasara, Banswara
ATC Farm, Chittor
Jalampur, Chittor
Pratapgarh
Pratapgarh
Dungarpur
Dungarpur
Aaspur, Dungarpur
Kumbhalgarh, Rajsamand
Gundi ka Bhilwara, Rajsamand
Majera, Rajsamand
Jaisamand, Udaipur
24° 34' 16 N 73° 41' 29 E
24° 34' 07 N 73° 39' 13 E
24° 34' 15 N 73° 40' 52 E
24° 34' 06 N 73° 41' 21 E
24° 21' 39 N 73° 32' 18 E
24° 21' 39 N 73° 32' 18 E
24° 56' 15 N 73° 49' 11 E
24° 34' 16 N 73° 41' 29 E
24° 08' 12 N 74° 03' 12 E
24° 37' 28 N 73° 53' 36 E
25° 21' 14 N 74° 34' 45 E
25° 21' 14 N 74° 34' 45 E
25° 21' 14 N 74° 34' 45 E
23° 21' 09 N 74° 38' 28 E
23° 21' 09 N 74° 38' 28 E
24° 48' 01 N 73° 26' 31 E
23° 32' 42 N 74° 26' 31 E
23° 32' 42 N 74° 26' 31 E
24° 53' 47 N 74° 37' 58 E
24° 53' 02 N 74° 38' 06 E
24° 02' 11 N 74° 46' 49 E
24° 02' 11 N 74° 46' 49 E
23° 51' 06 N 74° 10' 51 E
23° 51' 06 N 74° 10' 51 E
23° 56' 54 N 74° 05' 30 E
25° 08' 51 N 73° 35' 00 E
25° 00' 04 N 73° 50' 52 E
24° 46' 49 N 73° 44' 49 E
24° 14' 40 N 73° 57' 11 E
Wild
Wild
Farm land
Farm land
Wild
Wild
Wild
Wild
Farm land
Farm land
Farm land
Farm land
Farm land
Wild
Wild
Wild
Farm land
Farmland
Farm land
Wild
Farm land
Farm land
Wild
Wild
Farm land
Wild
Farm land
Farm land
Wild
INDIAN J BIOTECHNOL, JANUARY 2012
56
isopropanol and washed twice with 70% ethanol. The
pelleted DNA was air dried and stored at –20°C.
DNA concentration was determined using known
amount of λ DNA as standard.
RAPD Amplification
PCR amplification was performed with 52 random
decamer primers obtained from Operon Technologies
(Almeda, USA). Amplification was performed in
10 µL reaction volume containing 2.5 ng DNA,
1× PCR buffer (10 mM Tris pH 9.0, 50 mM KCl,
1.5 mM MgCl2 ), 100 µM each dNTP, 0.4 µM of
RAPD primer and 0.3 U of Taq DNA polymerase
(Bangalore Genei, India). PCR reactions were
performed in a Gene Amp 9700 Thermal Cycler
(Perkin Elmer Applied Biosystems) with an initial
denaturation at 94°C for 3 min, followed by 45 cycles
at 94°C for 45 sec, 36°C for 45 sec and 72°C for 2
min with a final extension at 72°C for 7 min.
Amplified products were separated on 1.5% agarose
gel in 1× TAE buffer by electrophoresis at 100 V and
visualized with ethidium bromide staining. The size
of the amplification products was determined by
comparison to λ DNA digested with EcoRI and
HindIII.
ISSR Amplification
PCR amplification was performed with 26 ISSR
primers (University of British Columbia, Vancouver,
Canada). The PCR reaction mixture (10 µL) consisted
of 2.5 ng DNA, 1× PCR buffer (10 mM Tris pH 9.0,
50 mM KCl, 1.5 mM MgCl2 ), 0.2 µL of 25 mM
MgCl2, 200 µM of each dNTP, 0.4 µM of ISSR
primer and 0.6 U of Taq DNA polymerase (Bangalore
Genei, India). PCR amplifications were performed
with initial denaturation at 94°C for 4 min, followed
by 35 cycles of 30 sec at 92°C, 1 min at annealing
temperature (depending upon the primer), 2 min
elongation at 72°C and final extension at 72°C for
7 min. The amplified products were electrophoresed
in 1× TAE buffer at 100 V on a 1.8% agarose gel
using EcoRI and HindIII double digest as mol wt
standard.
Statistical Analysis
The DNA fingerprint patterns obtained were
converted into binary data matrices containing arrays
of 0s and 1s. The RAPD and ISSR bands were scored
visually for the presence (1) or absence (0) of bands
of various mol wt sizes. Only polymorphic and
reproducible bands were considered for the analysis.
Data were analysed using SIMQUAL route to
generate Jaccard’s similarity coefficient using
NTSYS-pc version 2.02e22
(Numerical Taxonomy
System). Similarity matrices were utilized to construct
dendrograms independently for both the marker
systems and also on pooled marker data using
UPGMA (Unweighted Pair Group Method with
Arithmetic Average) algorithm and SAHN clustering.
Finally, a principal coordinate analysis was performed
in order to highlight the resolving power of the
ordination. A two (2-D) and three dimensional (3-D)
principal component analysis was constructed
to provide another means of testing the
relationships among accessions using EIGEN
program (NTSYS-PC).
The robustness of each phenogram was evaluated
by a bootstrap analysis23
of each data set using the
computer program WINBOOT24
. Each phenogram
was reconstructed 1000 times by repeated sampling
with replacement. The frequency with which a
particular grouping was identified was taken to reflect
the strength of the grouping.
Results
PCR fingerprinting of J. curcas DNA produced
clear, reproducible and polymorphic banding patterns
that allowed characterization of accessions used in the
present study. In case of RAPD analysis, 52 RAPD
primers were used for initial screening of J. curcas
genotypes, of which 47 primers revealed polymorphic
banding patterns. The 47-decamer primers amplified
DNA fragments across the 29 genotypes with the
number of amplified fragments varying from 2
(OPJ-06) to 24 (OPC-04) (Fig. 1a) in the molecular
size range of 100-3,500 bp. A total of 552 bands were
produced that could be scored, out of which
334 bands were polymorphic with an average of
7.1 polymorphic bands per primer. Percent
polymorphism ranged from 22.2 (OPE-01) to 100%
(OPH-02, OPU-09 and OPE-16) with an average of
60.5% polymorphism (Table 2). Similarity matrix
values using Jaccard’s coefficient ranged from
0.31, between U3 and U10, to 0.85 between DI and
D2, and R1 and R2. At 60% similarity, the accessions
separated into six clusters (Fig. 2a). Cluster I
comprised of most of the genotypes. Accessions U9
and U10 remained as outliers and showed maximum
variation (65%) from other genotypes. The result of
principal coordinate analysis was comparable to the
cluster analysis (Fig. 3a).
KHURANA-KAUL et al.: GENETIC DIVERSITY IN J. CURCAS L.
57
Of the 26 ISSR primers screened, 25 produced
336 amplification products, out of which 201 were
polymorphic with an average of 8.0 polymorphic
bands per primer. The number of bands amplified per
primer varied between 7 (UBC-817, -823) and
20 (UBC-835) with average band size between
100-3,500 bp (Fig. 1b). Percentage polymorphism
ranged from 18.2 (UBC-855) to 100% (UBC-828)
with an average of 59.8% polymorphism (Table 2). A
dendrogram based on UPGMA analysis with ISSR
data is shown in Fig. 2b. Jaccard’s similarity
coefficient ranged from 0.24 to 0.90. Dendrogram
Fig. 1 (a & b)—a. RAPD profile of J. curcas genotypes produced with primer OPC-04 (M, λ DNA double digest with EcoRI and HindIII
REs; Nc, Negative control (no DNA); & lanes 1 to 29, Samples used in the study as listed in Table 1); b. ISSR profile of different J.
curcas genotypes produced with primer UBC-880 [M, λ DNA double digest with EcoRI and HindIII Res; Nc, Negative control (no
DNA); & lanes 1 to 29, Samples used in the study as listed in Table 1]
Table 2—Comparison of DNA marker systems in J. curcas L.
Marker system No. of primers used Total bands scored Total no. of
polymorphic bands
% polymorphism Av. polymorphism
[bands primer-1]
RAPD
ISSR
RAPD+ ISSR
47
25
72
552
336
888
334
201
535
60.5
59.8
60.2
7.1
8.0
7.4
INDIAN J BIOTECHNOL, JANUARY 2012
58
Fig. 2 (a-c)—Dendrograms (UPGMA) representing genetic relationships among 29 accessions of J. curcas using Jaccard’s similarity
coefficients: a. RAPD databased dendrogram; b. ISSR databased dendrogram; & c. Combined (RAPD+ISSR) databased dendrogram.
(Numbers on the nodes of the cluster indicate the bootstrap values generated by 1000 replications using the program WINBOOT. Only
bootstrap values higher than 30% are shown. The labels represent the accession codes as given in Table 1.)
KHURANA-KAUL et al.: GENETIC DIVERSITY IN J. CURCAS L.
59
analysis separated the accessions into five clusters at
63% similarity. Cluster I comprised of 24 operational
taxonomic units (OTUs). The highest value of
similarity coefficient (0.90) was detected between
accessions A1 and A2. Accession U10 had distinct
OTU as in case of RAPD analysis. The result of PCA
was comparable to cluster analysis (Fig. 3b).
The RAPD and ISSR data were combined for
UPGMA cluster analysis. Dendrogram constructed on
the basis of RAPD+ISSR polymorphism separated the
accessions into six distinct clusters at 37% variation
(Fig. 2c) with Jaccard’s similarity coefficient ranging
from 0.30 to 0.85. Group I was the largest cluster and
consisted of 24 accessions. Group II, III, IV, V and VI
consisted of one accession each. The PCA analysis
based on RAPD+ISSR polymorphism grouped the
accessions into seven clusters (Fig. 3c). A few
differences in clustering were observed with UPGMA
clustering and principal coordinate analysis.
Accessions U11, B1, B2, B3 and S1 were grouped
separately from cluster I in PCA. The matrices for
two markers, RAPD and ISSR were also compared by
using Mantel’s test25
and the correlation value
between the matrices were found high (r=0.8623),
indicating good correlation between the two
molecular marker systems.
Discussion Knowledge about degree of genetic diversity
among and within natural population in and outside
centre of origin is required to gain the first idea about
where to find potentially valuable genetic material.
RAPD and ISSR studies have been widely used for
population genetic studies in both wild26-28
and
cultivated29-30
plants. During the present study,
47 RAPD and 25 ISSR primers produced
535 polymorphic bands that discriminated 29
J. curcas genotypes into six clusters. Both RAPD and
ISSR markers exhibited >50% polymorphism, which
is in contrast to the earlier reports18-19
where the
polymorphism detected with these markers was low.
This low level of variation of J. curcas in India has
been attributed to the small number of introductions
and their vegetative propagation. It is interesting to
note that irrespective of the type of marker used the
accession U10 showed genetic dissimilarity in both
phenogram as well as PCA.
Both UPGMA-phenogram as well as PCA (based
on combined RAPD+ISSR data) displayed similar
grouping of accessions with some minor deviations
Fig. 3 (a-c)—3-D plot of 29 accessions of J. curcas by principal
coordinate analysis using Jaccard’s similarity coefficients: a.
RAPD markers; b. ISSR markers; & c. Combined markers from
RAPD and ISSR analysis. (The labels represent the accession
codes as given in Table 1)
INDIAN J BIOTECHNOL, JANUARY 2012
60
but failed to show any pattern of variation that can be
related to geographic location of the accessions. A
possible explanation for this difference is that the two
marker techniques target different portions of the
genome. The ability to resolve genetic variation
among different genotypes may be more directly
related to the number of polymorphisms detected with
each marker technique rather than a function of which
technique in employed31
. UPGMA-phenogram
classified the accessions into six clusters, while PCA
grouped them into seven clusters as shown in other
studies also18
. The phenogram showed grouping of 24
out of 29 accessions studied (82.75%) into a single
cluster. The PCA results corresponded well with the
grouping of accessions based on cluster analysis with
minor deviations. This association of genotypes from
contiguous regions may be the result of similar agro-
climatic conditions or due to seed movement and gene
flow32
. The phenogram showed highest genetic
similarity (Jaccard’s similarity coefficient 0.85)
between accessions UI and U2, and R1 and R2, that
have come from Udaipur and Rajsamand locations.
The higher genetic similarity indicates the higher
probability of origin of all these accessions (U1, U2,
R1 and R2) from the same source and eventually
distribution to different locations. To find the
robustness and stability of the phenogram to group
accessions in different clusters, the data were
analyzed for bootstrap analysis with 1,000 replicates.
Higher bootstrap values (>30) obtained at all major
nodes in phenogram indicate the stability of grouping
of accessions in different clusters.
Our study indicates a modest level of genetic
variation in the J. curcas accessions as revealed by
RAPD and ISSR marker techniques. Similar
conclusions were made by Gupta et al33
and
Subramanyam et al34
while assessing genetic variation
in various J. curcas accessions collected from
different agro-climatic regions of India. This could be
used for estimation of genetic relationships, which
ultimately help in characterization of J. curcas
germplasm. This would also aid in developing and
planning breeding strategies for this plant by helping
breeders to identify diverse genotypes and makes it
possible to carry out early selections and thus reduce
the time between recurrent selections and increase
genetic gains per year.
Acknowledgement V K-K thanks Council of Scientific and Industrial
Research, New Delhi for the award of SRF and
Dr M Sujatha, Directorate of Oilseeds Research,
Rajendranagar, Hyderabad for technical guidance.
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