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  Selection

Selection:

Selection is one of the oldest techniques in which individual plants or group of plants are sorted out from varied population, so eliminating not wanted ones.  Selection methods are of two sorts. They are:

Mass selection:
In mass selection method, plants are selected based on their wanted morphological characters (phenotype). Their seeds are composite/mixed and the progenies are grown up in masses. They are not independently checked. Later than repeated selection for approximately five to six years, chosen seeds are multiplied and distributed to farmers. The only drawback of mass selection is that it is hard to differentiate hereditary variation from environmental variation.

Pure line selection:
It is a collection of plants acquired like a result of repeated self-pollination from a single homozygous individual.  Therefore, a variety created through this method displays more homozygosity with respect to all genes. One drawback is that new genotypes are never formed through this method. Genetic variability is necessary for adaptations in dissimilar environmental and seasonal conditions.

Clonal selection:
Crops such as sugarcane, potato, tea, banana and specific species of grasses are asexually propagated and generate very poor seeds. Based upon their phenotypic appearance, the method of clonal selection is used to choose enhanced variety from a mixed population (clones). Chosen plants are multiplied by vegetative propagation to give increase to a clone. The genotype of a clone remains same for a long period of time.

We have various varieties of crops like maize, tobacco, tomato, potato and brinjal that were introduced from countries like America, China and Australia. Introduced varieties occasionally do not get adjusted simply with our local environment. It requires some time for these introduced crops to settle. Occasionally, it is necessary to choose suitable and wanted variety from the introduced plants. For instance, a mung Phaseolus mungo variety was taken place from China but was not providing good yield and generated dull coloured seeds. From between the introduced mung crop, a plant unexpectedly produced large and bright coloured seeds. This feature may be because of sudden mutation. This variant plant was chosen and additional subjected to inter or intra specific crosses with our native crop. In this method, new varieties were generated and released as newly developed mung variety.

 

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