Glossary Plant Breeding

Early Generation Testing. Also called early testing; the evaluation of breeding materials
for specific characteristics during early segregating generations (F 2 , F 3 , and F 4 )based
on certain parameters. Early testing in maize refers to testing of inbred lines during I1,
I2, and I3 (S1/S2/S3) generations. The objective is to enhance the possibility of finding
superior inbred line by eliminating poor materials during early generations. It also
helps save extra expenditure. When materials are visually selected, it is a good
exercise for isolating families of high combining ability. It has been criticised on the
ground that the performance of inbred lines may change with the degree of
homozygosity attained by those inbreds. It is also not desirable when high combining
lines are agronomically poor, and are likely to be eliminated during inbreeding.
Ear-to-Row Selection. A form of selection in which desired ears are harvested
individually and subsequently grown an ear-to-a row, and the cycle is repeated from
the aggregate of seeds of selected rows. It differs from mass selection in basing the
selection on the performance of progeny.
Ecdysone. A molting hormone in insects.
Ecological Combining Ability. The ability of a genotype to perform synergistically in
association with other genotypes in mixed populations. Such genotypes are good
neighbours, and at the same time they are good competitors as well. In such mixed
populations, natural selection may be operating for superior neighbourhood; however,
in competition, it also appears to perpetuate many surviving genotypes with superior
pure-line performance.
Ecology (Haeckel 1869). The study of pattern of relations between organisms and their
environment. It has been derived from Greek words: oikos and logos, meaning
household and study, respectively. Thus the study of the environmental house
includes all the organisms in it and all of the functional processes that make the house
habitable. Literally, then, ecology is the study of life at home with emphasis on
totality.
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