Geoscience Reference
In-Depth Information
for agricultural scientists. Plant breeding has made remark-
able progress in increasing crop yields for over a century by
developing suitable cultivars, varieties and hybrids for various
crops. Plant breeding along with biotechnological approaches
like MAS will play a key role in this coordinated effort for
increased food production. Despite optimism about contin-
ued yield improvement from conventional breeding, with the
advancement of agricultural biotechnology, there is a need to
maximise the probability of success (Ortiz 1998). One area of
biotechnology, that is, DNA marker technology, derived from
research in molecular genetics and genomics, offers great
promise for plant breeding. Owing to genetic linkage, the DNA
markers can be used to detect the presence of allelic variation
in the genes underlying these traits.
Molecular markers are widely accepted as potentially valu-
able tools for crop improvement in major cereal crops like rice
(Mackill et al. 1999), wheat (Koebner and Summers 2003),
maize (Tuberosa et al. 2003), barley (Williams 2003), and also
in other important crops like tubers (Barone 2004), pulses (Kelly
et al. 2003; Svetleva et al. 2003), oilseeds (Snowdon and Friedt
2004), horticultural crop species (Baird 1995; Baird et al. 1997;
Mehlenbacher 1994) and pasture species (Jahufer et al. 2002).
Some studies suggest that DNA markers will play a vital role in
enhancing global food production by improving the efficiency of
conventional plant breeding programs (Kasha 1999; Ortiz 1998).
Although there has been some concern that the outcomes of
DNA marker technology as proposed by initial studies may not
be as effective as first thought, many plant breeding institutions
have adopted the capacity for marker development and/or marker-
assisted selection (MAS) (Eagles et al. 2001). An understanding of
the basic concepts and methodology of DNA marker development
and MAS, including some of the terminology used by molecu-
lar biologists, will enable plant breeders and researchers working
in other relevant disciplines to work together towards a common
goal—increasing the efficiency of global food production.
Construction of
linkage maps
A variation observed in the field does not always give any conclu-
sive indication about variation at genome level. These genotypic
variations cannot be visualised by the naked eye. Then comes
the need for certain landmarks that can be linked to our trait
of interest. Hence, mapping (i.e. determining the exact location
of the gene influencing a trait) is necessary for constructing a
framework for a particular plant genome with the help of mark-
ers. So, the foremost method used was the bi-parental mating
method to link a trait with the marker (linkage map). A linkage
