Article

Marker assisted selection for biotic stress resistance in wheat and rice

Indian Journal of Genetics and Plant Breeding (Impact Factor: 0.2). 01/2009; 69:305-314.

ABSTRACT Abstract
Use of molecular markers has emerged as a powerful and
efficient approach to complement traditional plant
breeding for improving crops. An array of molecular
markers are now available that include RFLP that is based
on Southern blot hybridization and, RAPD, ISSR, SSR and
STS are based on polymerase chain reaction. The AFLP
and CAPS markers are the other PCR based markers
involving pre and post amplification restriction digestion,
respectively. The most recent marker system is single
nucleotide polymorphism (SNP) that utilizes the vast DNA
sequence resources available in different crop species.
Each of these markers has its own strengths and
limitations. Markers are being used in several different
aspects of crop improvement including estimation of
genetic diversity, construction of high density genome
maps, mapping and tagging of genes, map-based isolation
of genes and marker assisted selection (MAS). MAS is
carried out for transferring target gene(s) from one genetic
background to another using tightly linked markers
(foreground selection). MAS is also carried out to quickly
recover recurrent parent genome in backcross breeding
using a large number of either random or mapped markers
having whole genome coverage (background selection).
Hence, MAS requires markers tightly linked to the genes
for the target traits as well as high-density genome maps
in crops of interest. This condition is not fulfilled in all
crops and traits. The Division of Genetics, IARI has taken
a lead in this approach in breeding for rust resistance in
wheat, blight and blast resistance in rice. MAS has been
effectively employed in pyramiding identified genes
involving short breeding cycles through background and
foreground selection thereby adding resistance to
established cultivars of each crop.

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