Marker-assisted selection (MAS) techniques
(Box 1) are free of the political issues that have
plagued the application of GM technologies.
MAS involves using variation at the DNA level
to track and monitor specific regions of the ge-
nomes during crossing and selection (14). The
greatest benefit of MAS occurs where the target
traits are of low heritability, are recessive in
nature, and involve difficult and costly phenotyp-
ing, and where pyramiding of genes is desired for
results such as disease and pest resistance. In
these cases, MAS is likely to be more reliable,
more convenient, or cheaper than phenotype-
based selection, and MAS currently provides the
only viable method for gene pyramiding. Molec-
ular markers are also important in analyzing the
mode of inheritance of certain traits and assessing genetic diversity. In cases where desirable
traits are closely linked and in repulsion, markers
can be critical in selecting rare recombination
events.