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inherited traits than for polygenic traits, with the development
and introduction of reliable PCR-based markers such as SSRs
and SNPs, in several crop plants, efficiency of genotyping
large populations or breeding materials have been significantly
increased. Through crop genomics research, marker-assisted
foreground selection is already gaining rapid momentum as
allele-specific markers on a number of agronomically important
traits (Collard and Mackill 2008). The assurance of MAS for
improving polygenic traits in a quick time-frame and in a cost-
effective manner is still elusive. There is a wider appreciation
that by simply indicating that a complex trait can be dissected
into QTLs and mapped to approximate genomic locations using
DNA markers would not serve the ultimate goal of plant trait
improvement. According to Young, research on quantitative
traits need to employ larger population sizes, multiple replica-
tions, better scoring methods and environments, appropriate
quantitative genetic analysis, various genetic backgrounds and,
whenever possible, independent verification through advanced
generations or parallel populations. The MAS strategies may
put more emphasis on reducing the number of crosses and sim-
ple selection steps to maximise their impact in the agriculture
(Collard and Mackill 2008).
In the present scenario, 'functional genomics' is making rapid
changes for dissecting the function of genes through genome-
wide experimental approaches. The tools such as DNA chips,
microarrays and expressed sequence tags aid in the quantitative
estimation of RNA levels. These RNA expression profiles will
help the breeders in selecting the better genotypes with desired
gene influencing a trait (Collard and Mackill 2008).
In the future, a greater coordination is required between
the workers of molecular breeders and quantitative geneticists
to build up and validate hypotheses involving complex gene
interactions. Bioinformatics also plays an important role in
facilitating these two branches. Thus, by integrating functional
genomics, bioinformatics and molecular breeding may cre-
ate fundamental revolutions in varietal improvement of crops.
Solutions to the above-mentioned obstacles of MAS need to
be developed in order to achieve a greater impact. The follow-
ing points need to be considered for high efficiency of marker-
assisted selection (Collard and Mackill 2008).
•
The workers of conventional breeding and molecular
breeders should work collectively to bridge the gap.
•
QTL mapping studies need to be implemented very care-
fully, and QTLs with high LOD with greater phenotypic
