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Molecular Plant Breeding 2013, Vol.5, No.3, 10
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13
87% as reported (Bhat et al., 1999) in case of sesame
and lower than 100% as reported (Salazar et al., 2006).
Abdelmigid et al. (2012) reported a percentage of
polymorphism to be 87% with 13.4 polymorphic
fragments in
B. napus
comparable to that of 91.2
polymorphism percentage and 15.73 bands per primer
reported in this study. 97.66% polymorphism was
reported for 16 primers by Ahmad et al., 2009. In
other studies, percentage of polymorphic primers in
mustard reported (Ali et al., 2007) was in the range of
21.54 to 59.36%; exactly similar polymorphism
percentage i.e. 21.54 to 59.36% was found by Khan et
al., (2011). Twenty one unique bands were obtained
for twelve out of fifteen primers in some of the
varieties. These unique bands have high potential
value since these can be converted to sequence tagged
site markers (STS) and sequence characterized
amplified regions (SCARs). Moreover, exclusive
bands can be proved valuable to discriminate these
cultivars at the molecular level without using field
data (Fernandez et al., 2002). Thus, it is suggested that
twelve primers used in the present work showing
unique bands can be used for obtaining genotype
specific profiles.
PIC calculated for these primers is 0.303 which is
comparable to 0.37 PIC value reported by Salazar et al.
(2006) in sesame. However, Russel et al. (1997)
obtained a very high value of PIC i.e. 0.5, greater than
PIC, reported in the present investigation. On an
average, marker index and resolving power i.e. 4.44
and 6.89 respectively obtained in the present study
were greater than that of 2.79 MI and 4.26 Rp values
obtained in case of sesame (Salazar et al., 2006). A
strong correlation has been observed in this study
between marker index, resolving power and
polymorphic information content which contradicts
non- significant relationships observed from the
findings of Salazar et al. (2006).
Higher numbers of polymorphic bands obtained
confirm a wide range of genetic diversity among
existing species. Cluster I comprise of four genotypes
belonging to different species chosen for authenticity
of this work. RSPT-1 (
B. campestris
variety) is
relatively divergent from rest of three varieties. Two
B.
napus
varieties i.e., RSPN-28 and DGS-1 are closely
related in the sub cluster, however, relatively distant
from CCS-08 (
B. oleracea
variety). The dendogram
presented in figure 2, clearly indicated that two
closely related
B. napus
varieties are intermediate
between
B. campestris
and
B. oleracea
varieties. This
could be imputed to the fact that
B. napus
(AACC) is
an amphidiploid species originated through the
spontaneous hybridization of
B. campestris
(AA) and
B. oleracea
(CC) comprising the full chromosome
compliments of its two progenitors. Cluster II consist
of all the 23
B. juncea
genotypes having two main
clusters, one comprised of only four varieties and
other constituted of 17 varieties. In cluster II, two
varieties i.e. RB-55 and CS-56 are found to be the
most divergent and varieties like RH-30 and RH-0406,
RB-50 and BR-24, RH-0749 and RH-0119 are closely
associated.
Conclusions
The analysis with RAPD markers disclosed wide
variation within mustard and proved to be suitable for
use with
Brassica
species. However, molecular
approach is more likely to generate an unbiased
picture of diversity than an agro-morphological one.
Molecular characterization should be seen as
equilibrating the traditional approach because most
desirable traits are the result of interaction among
expressed genes. That is why, morphological studies
are still critical for discrimination of cultivars. The
present findings further strengthened previous reports
that the RAPD markers can be used effectively to
estimate genetic differences among genotypes.
Genetic variation existing among selected genotypes
of
B. juncea
can further be utilized in strengthening
Brassica
breeding programs. The present study can
provide further assistance in developing and planning
breeding strategies by understanding relationship
among species taken into consideration.
Materials and Methods
Plant Material
Twenty seven genotypes of
Brassica
species (23
Brassica juncea
genotypes, 2
Brassica napus
genotypes
and one each of
Brassica campestris
and
Brassica
oleracea
) were considered in the present study
(detailed in Table 2). The seed material was procured
from different institutes of Northern India.