Glossary Plant Breeding

Eugenics. Controlled human breeding in an attempt to improve future generations, based
on notions of desirable and undesirable genotypes. During early part of twentieth
century, it became quite fashionable to propose that persons having genetic disorders
should be prevented from having any offspring (a programme called negative
eugenics). Most deleterious alleles are rare, and mostly occur in heterozygotes.
Assuming frequency of 0.01 of a deleterious allele, it takes about 100 generations to
reduce its frequency to half, that is, 0.005 {q n = 1/(n+1/q 0 )}, if all the homozygotes
were prevented from producing offspring. Clearly, it was a futile exercise.
Eukaryote. A cell having true nucleus. The cell has cytoplasm separated by a distinct
nuclear membrane.
Euploidy. A situation wherein an organism has any number (one, two or more) of
complete chromosome sets; such an individual is called euploid. It covers situations
such as monoploidy, diploidy, and polyploidy.
Euthenics. Improvement in conditions for people to live in.
Ever Green Revolution. Achievement of sustainable productivity advances, rooted in
the principles of ecology, economics, social and gender equity, and employment
generation. It is a concept that applies to improvement in crop productivity in
perpetuity without ecological harm.
Evolution. Gradual change usually with a directional component. Biological evolution is
best defined as the gradual change in the diversity and adaptation of populations of
organisms. It involves change in gene frequencies, which results from (a) selection
pressure from the environment and interacting species, (b) recurrent mutation, (c)
genetic drift, and (d) migration. The process of evolution has two dimensions:
Phyletic evolution and speciation. Phyletic evolution is the gradual changes that occur
with time in a single lineage of descent; as a rule, these changes result in greater
adaptation to the environment and often reflect environmental changes. Speciation
occurs when a lineage of descent splits into two or more new lineages and is the
process that accounts for the greater diversity of the living world. Biological evolution
is quite distinct from cultural evolution that is a unique human process and is a rapid
process compared to the biological evolution. Human beings may evolve culturally
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