Glossary Plant Breeding

INSA. International Seed Testing Association founded in 1924 for ensuring uniformity in
seed testing. ISTA rules for seed testing are used all over the world by its member and
non-member countries. It has a system of international and regional referee testing
through which the participating stations can appreciate their shortcomings. It issues
different kinds of certificates, which (especially orange international certificates) are
used extensively, and are of great importance for the international trade in seeds.
Insertion Sequence. A mobile piece of bacterial DNA that is capable of inactivating a
gene into which it inserts. It may be several hundred nucleotide pairs in length.
Insertional Translocation. The insertion of a segment from one chromosome into
another nonhomologous one. The best-known classical example is transfer of a small
segment (gene?) from Aegilops umbellulata into our cultivated bread wheat for leaf
rust resistance. The detailed analysis by Sears (1956) showed that the segment
insertion occurred near to kinetochore of one of the chromosomes, and the genotype
was slightly later in maturity in addition.
Instability. Inconsistency in performance of a genotype(s) across years and locations. It is
a type of variation that appears to be random in direction. It may be due to
developmental noise. It has no genetic basis.
Integrated Pest Management. Exploitation of several pest suppression tactics to keep
the pest population below damaging threshold. It is a multidimensional approach
involving a range of biological, cultural, physical, biochemical and chemical
techniques to hold pest population below economically damaging levels without
disrupting the agro-ecosystem. In fact, the initial factor in IPM is pest resistance in
plant cultivars. Its use as a basal component in IPM has several advantages: (a) it
permits lower level of resistance in plant varieties, (b) by doing so, we can increase
the number of cultivars available for commercial cultivation, and (c) it reduces the
selection pressure for the development of pesticide resistant biotypes of insects, and
other components of IPM reduce the selection pressure for development of biotypes
that would infest resistant cultivars.
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