Basic HTML Version
Bioscience Methods 2012, Vol.3, No.2, 7
-
20
http://bm.sophiapublisher.com
8
Flowering is a major constraint for sugarcane
improvement by adopting breeding tool Khan et al
(2004). In Pakistan, flowering and viability are still a
major problematic issue due to lack of favorable
environmental conditions (Khan et al., 2007). Thus,
unavailability of viable fuzz makes this crop unsuitable
under the umbrella of conventional breeding in
Pakistan. In conventional breeding and selection
system, 10 to 15 years are tentative time span for
commercial release of variety with improved characters
James (2004).
Moreover, during vegetative propagation, the pathogens
keep on accumulating generation after generation,
which ultimately results in the decline of the variety.
Preservation of germplasm collections is an integral
part of all breeding programmes. Current methods
for this purpose include conservation stands and
greenhouse collections, requiring land and facilities,
which are labor intensive and expensive to maintain.
Furthermore, under such conditions, there is a high
risk of germplasm loss through natural disasters, pest
and disease infestations. Traditional plant breeding
techniques have been widely used to enhance
important economic traits in agronomic crops, but
this approach is laborious and time-consuming,
especially in vegetatively propagated species like
sugarcane. Moreover, various important traits such as
resistance to insects, viruses, and herbicides are often
absent from the normal sugarcane germplasm. DNA-
mediated plant transformation can serve an important
function to introduce useful genes into sugarcane that
otherwise would be difficult or impossible by standard
procedures.
Tissue culture plays an important role in crop
improvement. Sugarcane
in vitro
regenerants have
higher yield potential in terms of excellent sugar
recovery, high tiller ratio, more weight and excellent
ratooning performance (Comstock and Miller, 2004).
Through tissue culture successful attempts were made
to eliminate diseases in sugarcane. Sugarcane yellow
leaf virus (SCYLV) and sugarcane yellows phytoplasma
(SCYP) were eliminated in nineteen cultivars and
showed no disease attack for one year in green house
(Parmessur et al., 2002; Ramgareeb et al., 2010).
In
vitro
culture system is also used for screening of
diseases viz., eye spot disease, fiji disease and downy
mildew and whip smut in sugarcane (Singh et al.,
2005). One advantage of the use of sugarcane rolled
leaf and sheath tissue for embryogenic callus initiation
is that it is relatively easy to arrange year-round
availability of this explant type from field-grown
plants, so that fresh callus batches can be regularly
initiated to minimize time in culture for gene transfer.
By comparison with more recalcitrant related species
such as sweet sorghum (Raghuwanshi and Birch,
2010), the surface layers of sugarcane embryogenic
callus evidently have a higher proportion of cells that
are able to proliferate and regenerate under conditions
that permit the selection of transformed plantlets.
The application of plant biotechnology approaches
like genetic transformation of foreign genes into
the plant genome, it is very crucial to be the
optimization of efficient regeneration system in terms
of homozygous plantlet formation through tissue
culture with 100% purity to the mother plant.
Therefore, assessment of the genetic stability of
in
vitro
regenerated planets is an important step in the
application of biotechnology. For the application of
in
vitro
culture system and clonal propagation, it is
important to determine genetic purity (Rani et al.,
2000). Hence testing the genetic homogeneity of
in
vitro
regenerated plants is very essential and important.
The use of molecular markers is becoming widespread
for the identification of somaclonal variants and the
assessment of in vitro regeneration protocols (Taylor
et al., 1995). Different molecular markers (ISSR,
RAPD, Trap, RFLP, AFLP and microsatellites etc) are
used to detect and characterize somaclonal variation at
the genomic DNA level by Ford-Lloyd et al (1992)
and Cloutier and Landry (1994).
Among the various molecular marker techniques,
RAPD marker is found to be the most useful one to
detect genetic changes at DNA level by Taylor et al
(1995); Soliman et al (2003) and Anand (2003).
RAPD analysis technique is the quick, simple, easy to
perform, require small amount of DNA for analysis
and the most important advantage of this marker is
that the independence of prior information requirement