Glossary Plant Breeding

&LD 50 ) go high for genotypes that are fairly tolerant to abiotic stresses such as heat,
drought, cold, etc.
Grade. A unit of biological improvement from evolution point of view consisting of a
group of individuals similar in their level of organization.
Gradient. A gradual change in some quantitative property over a specific distance.
Grafting. A process of producing a chimera by vegetative fusion of parts (the scion and
stock) from different individuals.
Graft-Hybrids. Plants in which tissues of different genotypes exist side by side. In such
hybrids, some tissues (cell layers) come from the scion and some from the stock.
Gray. The SI unit of absorbed dose, typically associated with ionising radiation such
as X-rays or gamma particles or with other nuclear particles. Gray (Gy) is defined as
the absorption of one joule of such energy by one kilogram of matter (usually human
tissue). Gray, named after the British physicist Louis Harold Gray, replaces the
traditional unit, the rad (equivalent to 0.01 Gy).
Green Revolution. Sudden and quantum jump in the production and productivity of
agricultural crops. Dr William Gadd of the USDA coined the term in 1968. That year,
India experienced its first quantum jump (almost double to that of preceding year, that
is, about 17.0 million tons) in wheat production, leading to Indian Government
releasing a special stamp titled “wheat revolution”. Significantly, the stamp had the
portrait of the library of IARI, New Delhi to mark the importance of scientific and
knowledge inputs in farming. The Green Revolution started at first in the Punjab-
Haryana regions owing to the presence of several prerequisites such as owner
cultivation, land consolidation and levelling, rural communication and electrification,
existence of a dynamic research and extension system, assured and remunerative
marketing opportunities, and the like.
Gridding. A technique to reduce the selection error caused by environmental effects. It
consists of dividing the experimental area into small plots (grids) and selecting equal
number of superior plants within each grid regardless of the fertility and moisture
gradients. Thus it aids to efficiency of mass selection.
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