Answer:
Plant breeding programmes are carried out
in a systematic way world wide-in government institutions and commercial
companies.
The
main steps in breeding a new genetic variety of a crop are
(i)
Collection of Variability Genetic variability is the root of any
breeding programme . In many crops pre-existing genetic variability is
available from wild relatives of the crop. Collection and preservation of all
the different wild varieties, species and relatives of the cultivated species
(followed by their evaluation for their characteristics) is a pre-requisite for
effective exploitation of natural genes available in the populations. The
entire collection (of plants/seeds) having all the diverse alleles for all
genes in a given crop is called germplasm collection.
(ii)
Evaluation and Selection of Parents The germ plasm is evaluated so as to
identify plants with desirable combination of characters. The selected plants
are multiplied and used in the process of hybridization. Purelines are created
wherever desirable and possible.
(iii)
Cross HybridizationAmong the Selected Parents The desired characters
have very often to be combined from two different plants (parents), e.g., high
protein quality of one parent may need to be combined with disease resistance
from another parent.
This is possible by cross hybridizing
the two parents to produce hybrids that genetically combine the desired
characters in one plant. This is a very time-consuming and tedious process
since the pollen grains from the desirable plant chosen as male parent have to be
collected and placed on the stigma of the flowers selected as female parent.
Also, it is not necessary that the
hybrids do combine the desirable characters, usually only one in few hundred to
a thousand crosses shows the desirable combination.
(iv)
Selection and Testing of Superior Recombinants This step consists of
selecting, among the progeny of the hybrids, those plants that have the desired
character combination. The selection process is crucial to the success of the
breeding objective and requires careful scientific evaluation of the progeny.
This step yields plants that are superior
to both of the parents (very often more than one superior progeny plant may
become available). These are self-pollinated for several generations till they
reach a state of uniformity (homozygosity), so that the characters will not
segregate in the progeny.
(v)
Testing, Release and Commercialization of New Cultivars The newly
selected lines are evaluated for their yield and other agronomic traits of
quality, disease resistance ,etc.
This evaluation is done by growing these
in the research fields and recording their performance under ideal fertilizer
application, irrigation and other crop management practices.
The evaluation in research
fields is followed by testing the materials in farmers' fields, forat least
three growing seasons at several locations in the country, representing all the
agro climatic zones when the crop is usually grown.
The material is evaluated in
comparison to the best available local crop. After evaluation the variety can
be relased for the farmers.
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