Glossary Plant Breeding

might save several hectares, and fewer generations may save several decades. MAS is
being used efficiently: (a) in gene pyramiding, (b) in marker-assisted alien gene
introgression, and (c) for simultaneous identification and pyramiding of QTLs from
primitive cultivars and alien species.
Markers (Morphological). Traits or genes (variant alleles), which are used to label a
biological system throughout the course of experimentation. These are usually mutant
alleles, which may be either dominant or recessive. These are limited in number,
influenced by environments, and developmental stage specific compared to molecular
markers. Further, they could appear as pleiotropic effect of other major genes.
Masking Action. Gene action such that a gene hides the effect of another non-allelic
gene (when both are present). In oats, for instance, Y produces yellow seed coat and B
produces black seed coat. The gene Y will have no effect in presence of B, since black
colour masks yellow ones. It gives a ratio of 12 black (B-Y-, B-yy): 3 yellow (bbY-): 1
white (bbyy).
Mass Pedigree Method. A system of breeding in which a genetically diverse population
is propagated in mass until conditions favourable for artificial selection occur, after
which pedigree selection is practised. The bulking may end as early as F 2 generation
or may be continued for many generations if the advent of conditions suitable for
selection is long-delayed.
Mass Selection. A form of selection in which individual plants are selected depending
upon their better phenotypic values (usually without progeny test) and the next
generation is propagated from aggregate of their seeds. In autogamous crop species, it
has basically two uses: First, it can effect improvement in land varieties very safely
and rapidly, and the second, it can be used to purify existing varieties. In the crosspollinated
species, it is used to improve characters having high heritability. It is
virtually powerless to effect any improvement in a trait like yield (low heritability)
obviously for three reasons: (a) selection is exclusively based on phenotype, (b) there
is lack of pollen control on female parent, and (c) there is no progeny test. Therefore,
simplicity of mass selection is the weakness in itself. However, some form of mass
selection is almost always practiced in most breeding methods.
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