VARIETAL DETERIORATION

DETERIORATION CAUSES OF CROP VARIETIES AND ITS CONTROL

Varietal Deterioration:- Permanent reduction either in the genetic or agronomic value of a released variety. There are several causes of deterioration of a variety which can be divided in to  two groups, viz, genetic causes and non genetic causes. Genetic causes include natural outcrossing, spontaneous mutations, residual variability and adaptive changes. Non genetic causes include mechanical mixture, disease infestation and adverse agro-climatic conditions. These factors are briefly described below:

Genetic Causes

1.     Natural Outcrossing:- Sometimes, the variety deteriorates due to natural outcrossing with another variety. In cotton, the degree of natural outcrossing depends mainly on the activity of honey bees. Recommended isolation distance should be maintained to prevent natural outcrossing.

2.     Spontaneous Mutations:- Spontaneous mutations constantly arise in crop varieties. Such mutants after crossing with true genotypes of a variety cause deterioration of that variety. Rouging is the effective way to prevent varietal deterioration by such mutations.

3.     Residual Variability:- Sometimes, residual variability exists in a variety at the time of its release. During later cycles of seed production this deteriorates the variety. Hence there should not be any residual variability at the time of releasing a variety.

4.     Adaptive Changes:- When the seed crop is grown in different agroclimates for several consecutive generations, developmental variations may set. A particular environment may favour some specific genotypes of a variety. This may lead to shift in the variety in a particular direction. To reduce the chances of such shift the seed of a variety should be produced in the area of its adaptation.

Non Genetic Causes

1.     Mechanical mixture:- Mixing of different varieties may takes place during sowing with seed drills, ginning, seed processing and storage. Such mixture is the most important source of varietal deterioration. This can be avoided by taking precautions during above mentioned operations.

2.     Disease infestation:- Sometimes, an improved variety deteriorates because it is infested by a disease to which it was considered resistant at the time of its release. This may result either due to a) Absence of such disease in the area where the variety was tested or due to b) formation of new race of a disease.

3.     Adverse agro-climatic conditions:- Under unfavorable soil and environmental conditions, the variety may not be able to express its full potential and show poor performance. Hence, a variety should be grown in the area of its adaptation only.

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Milan Tomic

Hi. I’m Designer of Blog Magic. I’m CEO/Founder of ThemeXpose. I’m Creative Art Director, Web Designer, UI/UX Designer, Interaction Designer, Industrial Designer, Web Developer, Business Enthusiast, StartUp Enthusiast, Speaker, Writer and Photographer. Inspired to make things looks better.

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