Glossary Plant Breeding

Spontaneous Mutation. A mutation occurring in the absence of mutagens, usually due to
errors in the normal functioning of cellular enzymes (which are normally required for
DNA replication).
Spore. A haploid cell destined to form or act either as a gamete or as the initial cell for a
new haploid individual. In plants and fungi, sexual spores are the haploid cells
produced by meiosis. In certain other fungi, asexual spores are somatic cells that may
act as gametes or initiate the development of a new haploid individual.
Sporocyte. A diploid cell undergoing meiosis to form haploid spores; a spore mother
cell.
Sporophyte. The diploid sexual-spore-producing generation or phase in the life cycle of
plants, that is, the stage in which meiosis occurs.
Sporophytic Incompatibility. A kind of mating wherein incompatibility reaction of the
pollen is governed by the genotype of the parent. The gene for incompatibility has
numerous alleles that may show dominance, individual action or competition in either
pollen or styles. This complex incompatibility reaction leads to (a) frequent reciprocal
differences, (b) occurrence of female sterility, and (c) homozygosity at the locus
concerned (for example, members of crucifereae).
Sport. In plant and animal breeding, an aberrant individual resulting from mutation. Bud
sport is a somatic mutation occurring in a bud.
Spurious Correlation. Associations between two variables, which are purely accidental
or arise due to chance factors. The two variables have no connection whatever.
(Population increase in India and England after 1947, for example).
Square. An unopened flower bud in cotton with its accompanying bracts.
SSLP. Short Sequence Length Polymorphism; the presence of different numbers of
short repetitive elements (mini- and microsatellite DNA) at one particular locus in
different homologous chromosomes. Heterozygotes for such SSLP represent useful
markers for genome mapping.
Stability. The consistency in the performance of a genotype(s) across environments with
respect to a characteristic(s). If genotype-environment interaction is zero, it means the
genotype is stable. Terms such as homeostasis and buffering have also been used to
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