Question

How has mutation breeding helped in improving crop varieties? Give one example where this technique has helped.

Answer 1

Mutation, an inherited alteration in the genetic characteristics of an organism, is a natural process that produces new gene variants (alleles). The mutation is the main cause of all genetic differences that occur in every organism, including plants. Variation thus produced by mutation provides the raw material for natural selection and is a driving force in evolution.

Complete answer:
Natural selection works to bring about the evolution of new races and animals through variability produced by natural mutations and intensified by the resulting recombination of genes during sexual reproduction. In addition to natural mutations that occur naturally due to different forms of radiation and cosmic rays obtained from the sun and also emitted by certain radioactive elements, mutations may also be artificially caused by several physical agents, such as gamma rays and x-rays, and by several chemical agents belonging to a few identified classes known as chemical mutagens. The standard technique of generating diversity by altering genes through the induction of mutations by physical or chemical mutagens and using the same successful methods of selection techniques in different generations for the enhancement of a specific crop species for the desired objectives is called mutation breeding. This is also done by plant breeders all over the world for crop enhancement.
The utility of mutation breeding in crop improvement was demonstrated first in Sweden, which embarked on the practical breeding of agricultural plants by X-ray and ultraviolet-induced mutations (Gustafsson, 1947). Swedish plant breeders have identified several mutations in barley chlorophyll through the use of x-rays. Some mutants characterized by thick heads, late maturation, and very stiff, taller straw have been discovered. These mutants have been found to yield higher yields and produce more straw than the maternal variety.
The effect of induced mutations on crop improvement is expressed in 3248 mutant varieties officially registered by the Food and Agriculture Organization/International Atomic Energy Agency carrying novel induced variation. As one of the top three countries closely trailing India, China, and Japan and contributing substantially to the number of mutant varieties published worldwide, India occupies a significant role among countries actively engaged in crop improvement through induced mutation techniques.
Mutation breeding in India has yielded significant dividends both in enhancing our awareness of the various mutagenesis processes related to crop improvement and in developing more than 345 improved mutant varieties belonging to 27 crop species. The most up-to-date list of 345 mutant varieties belonging to 57 crop species published in India clearly shows the significance and importance of the use of mutation breeding for crop improvement in India (Kharkwal and Shu, 2009). The four high yielding chickpea mutant varieties, Pusa-408, Pusa-413, Pusa-417, and Pusa-547, with resistance to Ascochyta blight, Fusarium wilt, and other diseases and pests, developed by the author at the Division of Genetics, ICAR-Indian Agricultural Research Institute, New Delhi and released by the Government of India for commercial cultivation, are the first-ever examples of the direct use of induced products.
The best examples of mutation breeding are Jiahezazhan and Jiafuzhan rice.

Note: The most significant benefit of mutation breeding is that unlike genetically modified GM products, the end products/varieties produced by mutation breeding do not bear any alien genes. It also has no negative environmental effects. As such, there are no problems adverse to human health, biosafety and public acceptance, etc. In reality, the breeding of mutations has worldwide acceptance.