Mutations and their Role in Crop Improvement | Agriculture Optional Notes for UPSC PDF Download

Introduction

Mutation breeding, a method of deliberately inducing heritable changes in the phenotype of crops, plays a crucial role in crop improvement. This article delves into the various aspects of mutation breeding, from its historical milestones to the types of mutations, mutagens used, and procedures involved. It also discusses the advantages, limitations, and achievements of mutation breeding, emphasizing its importance in enhancing crop varieties.

Milestones in Mutation Breeding

The concept of mutation breeding can be traced back to the early 20th century when notable achievements were made in this field.
Some of the significant milestones include:

• In 1901-1904, Hugo de Vries coined the term "Mutation" and discovered genome mutations in 'Oenothera.'
• In 1927, Muller pioneered the use of X-rays to induce mutations in Drosophila.
• Stadler, in 1928, applied X-rays to induce mutations in barley.
• In 1936, the first induced mutant variety, tobacco var. 'Chlorina,' was released in Indonesia, using X-rays.
• In 1946, Auerbach and Robson reported chemically induced mutations, notably using Nitrogen.

Types of Mutation

Mutation breeding encompasses two main categories of mutations: Spontaneous and Induced mutations. Induced mutations are further divided into Macro and Micro mutations, each with distinct characteristics.

Table: Comparison of Macro and Micro Mutations

Mutagens

Mutagens, either physical or chemical agents, are instrumental in enhancing the frequency of mutations. Physical mutagens include ionizing radiation (alpha-rays, beta-rays, X-rays, gamma rays) and non-ionizing radiation (ultraviolet radiation). Chemical mutagens comprise alkylating agents (EMS, MMS, etc.), acridine dyes, base analogues, and other mutagens like nitrous acid.

Procedures of Mutation Breeding

The successful implementation of mutation breeding involves several key steps:

• Choice of Material: Opt for the best available crop variety with pure seeds.
• Choice of Mutagen: Chemical mutagens are generally preferred.
• Part of the Plant to be Treated: Decide whether to treat seeds, pollen grains, vegetative propagules, corns, bulbs, or the entire plant.
• Dose of Mutagen: Determine the optimum mutagen dose that induces maximum mutations with minimal harm.
• Handling of Segregating Generations: Carefully manage the M1, M2, M3, and subsequent generations.

Table: Key Steps in Mutation Breeding

Achievements of Mutation Breeding

Mutation breeding has led to the development of numerous mutant crop varieties, enhancing various characteristics such as disease resistance, earliness, plant height, color changes, and adaptation to different environmental conditions. Some notable mutant varieties released in India include Sharbati sonara (Wheat), Jagannath (Rice), MA-9, MCU-7, Pusa ageti (Cotton), Pusa 408, Pusa 413, Pusa 417, Pusa 547 (Chickpea), and more. These varieties have contributed significantly to agricultural productivity.

Research Centers and Institutes

In India, several research centers and institutes have played a pivotal role in developing and releasing mutant varieties. Notable institutions include the Indian Agricultural Research Institute (IARI) in New Delhi, Bhabha Atomic Research Centre in Mumbai, Tamil Nadu Agricultural University in Tamil Nadu, and the National Botanical Research Institute in Lucknow, Uttar Pradesh.

Future Prospects

Advancements in molecular techniques, including DNA fingerprinting and molecular mapping, have revolutionized mutation breeding. In vitro culture and molecular methods have expanded the potential for crop improvement through mutation breeding, promising increased crop yields and agricultural sustainability.

Advantages and Limitations

Mutation breeding offers several advantages, such as being a cost-effective and rapid method for developing new varieties, inducing desirable mutant alleles, and improving oligogenic traits like disease resistance. However, it also has limitations, including the low frequency of desirable mutants, random and unpredictable processes, difficulty in identifying micro mutations, and the potential for negative pleiotropic effects on other traits. Health risks associated with the handling of chemical mutagens and radiation treatments are also a concern.

Conclusion

In a world where genetic diversity in crops has been gradually narrowing due to conventional breeding methods, mutation breeding serves as a vital approach for broadening genetic variation and improving crop varieties. Its cost-effectiveness, speed, and proven success make it an essential tool in ensuring global food security and enhancing livelihoods through improved crop varieties. Mutation breeding continues to be at the forefront of agricultural innovation, contributing to the ever-growing demands of our planet's population.