International Journal of Horticulture 2015, Vol.5, No.12, 1
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10
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number of polymorphic bands (45); whereas, primer
A10 provided the lowest number of polymorphic
bands (3). The variation among reproducible bands
generated by each primer depends on the primer
sequence and the extent of variation in the specific
genotypes (Upadhyay et al., 2004).
It is apparent from our results that genotypes Copi and
Eskandrani shared the highest number of RAPD
markers using the 10 primers used in this study which
represented also in the high similarity matrix
coefficient (0.891). This piece of information suggests
that their parental breeding lines were genetically
close to each other. Genotype Copi is maintained by
local farmers and it can be suggested that it is
originated as segregation population out of genotype
Eskandrani.
The high correlation between the similarity matrix and
the UPGMA dendrogram, indicates a good representation
of the relationship among the genotypes. On the basis
of the comparison between morphological and
chemical evaluation and RAPD molecular markers
results, a great deal of correspondence has been found.
The obtained clustering based on RAPD was consistent
with morphological and chemical characteristics of the
squash genotypes used in this study. However, in few
cases the clusters were not in agreement with the
known genetic background of such genotypes.
For instance, genotype Butternut which belong to the
winter squash (
Cucurbita moschata
L.) was assigned
to a cluster with other summer squash genotypes
which belong to (
Cucurbita pepo
L.) while, few
summer squash genotypes fall outside that cluster and
appear as distantly related to the rest of (
Cucurbita
pepo
L.) genotypes.
The RAPD assay has been successfully used in
taxonomic and genetic diversity studies of squash
(Al-Tamimi, 2014; El-Adl et al., 2012; Hadia et al.,
2008; Tsivelikas et al., 2009; Ntuli et al., 2013;
Baranek et al., 2000; Radwan, 2014). The technique
was found by former and by us to be suitable for use
with squash due to its ability to generate reproducible
polymorphic markers. Our study reports an additional
10 RAPD markers capable of distinguishing among
the squash genotypes, and extends the application of
those markers to the identification of the genetic
relationships as well as diversity and structure present
within those genotypes.
Germplasm characterization is an essential link between
the conservation and utilization of plant genetic
resources. Molecular DNA techniques allow researchers
to identify accessions at the taxonomic level, assess the
relative diversity within and among species and locate
diverse accessions for breeding purposes. Plant
breeders usually use efficient molecular marker tools
such as RAPD-PCR to organize their genetic resources
into related groups to make more informed decisions
regarding choice of parents in breeding programs.
Knowledge of genetic relationships when complemented
with phenotypic data can reveal source of desirable
characteristics in more closely related genotypes which
permit the recovery of the phenotype of the recurrent
parents in fewer breeding generations than would be
required for a more distantly related donor parent.
Knowledge of wide genetic diversity observed in
squash provides information that is important in the
management of germplasm resources for future breeding
programmes.
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