Describe the history of plant breeding in India. Write the objectives of plant breeding and methods for creation of variability for crop improvement.

History of Plant Breeding in India

The history of plant breeding in India can be broadly divided into three phases:

• Traditional Period (Pre-1930s): This phase was characterized by farmers’ selection based on observable traits. Farmers consciously selected seeds from plants exhibiting desirable characteristics like higher yield, better taste, or resistance to local pests and diseases. This was an unconscious form of selection, passed down through generations. Examples include the development of indigenous rice varieties and landraces.
• Early Scientific Period (1930s-1960s): The establishment of the Imperial Plant Breeding Institute (IPB), now the National Plant Breeding Institute (NPB), in Rajahmundry in 1930 marked the beginning of organized plant breeding. Initial efforts focused on introducing and adapting foreign varieties. The introduction of wheat varieties like 'Sonoran' from the US laid the foundation for future improvements. During this period, emphasis was on improving yield and disease resistance. The Indian Agricultural Research Institute (IARI), New Delhi, was instrumental in developing early varieties.
• Modern Period (1960s-Present): The Green Revolution, initiated in the mid-1960s, revolutionized Indian agriculture. The introduction of high-yielding varieties (HYVs) of wheat and rice, developed by the International Rice Research Institute (IRRI) and the Mexican Agricultural Research Institute (CIMMYT), dramatically increased food production. This involved extensive breeding programs and infrastructure development. Post-Green Revolution, the focus shifted towards improving quality traits, such as protein content, micronutrient levels, and stress tolerance. The advent of biotechnology and genetic engineering has opened new avenues for crop improvement in recent decades.

Objectives of Plant Breeding

The primary objectives of plant breeding have evolved over time, reflecting changing societal needs and technological advancements:

• Yield Improvement: Increasing the productivity per unit area is a primary objective, especially to meet the demands of a growing population.
• Disease and Pest Resistance: Developing varieties resistant to common diseases and pests reduces crop losses and minimizes the need for pesticides.
• Improved Nutritional Quality: Breeding for enhanced protein, vitamin, and mineral content addresses nutritional deficiencies. Biofortification, the process of increasing the nutrient content of staple crops, is a key focus.
• Adaptation to Environmental Stress: Developing varieties tolerant to drought, salinity, heat, and cold is crucial for ensuring stable yields under adverse conditions.
• Improved Maturity Duration: Reducing the time from sowing to harvest allows for multiple cropping cycles and better resource utilization.
• Improved Seed Size and Quality: Larger seed size and better germination rates contribute to easier handling and improved seedling establishment.
• Improved Agronomic Traits: Breeding for traits like lodging resistance (standing ability) and uniform plant height facilitates harvesting and reduces losses.

Methods for Creation of Variability

Creating genetic variability is the first and most crucial step in plant breeding. This variability provides the raw material for selection. The methods can be broadly classified into conventional and modern techniques:

Conventional Methods

• Introduction and Acclimatization: Introducing wild relatives or exotic varieties and observing their performance in local conditions.
• Mutation: Inducing mutations using chemical mutagens (e.g., EMS - Ethyl Methane Sulphonate) or physical mutagens (e.g., X-rays, gamma rays) to create new alleles.
• Hybridization: Crossing genetically dissimilar plants to create new combinations of genes. This is the most common method. Different types of hybridization include:
  • Intra-varietal hybridization: Crossing plants within the same variety.
  • Inter-varietal hybridization: Crossing plants between different varieties.
  • Inter-specific hybridization: Crossing plants between different species (often challenging due to reproductive isolation).
  • Intergeneric hybridization: Crossing plants between different genera (extremely challenging and rare).
• Polyploidy: Inducing polyploidy (e.g., doubling the chromosome number) to create new genetic combinations.

Modern Techniques (Biotechnology)

• Genetic Engineering (Transgenesis): Introducing genes from other organisms (even unrelated species) into a plant's genome to impart desired traits. Examples include Bt cotton (insect resistance) and Golden Rice (enhanced beta-carotene content).
• Genome Editing (CRISPR-Cas9): Precisely modifying genes within a plant’s genome. This technology allows for targeted gene modification and is rapidly transforming plant breeding.
• Marker-Assisted Selection (MAS): Using DNA markers linked to desired traits to select superior plants, accelerating the breeding process.
• Somaclonal Variation: Variation arising from tissue culture.

Method	Description	Advantages	Disadvantages
Hybridization	Crossing genetically diverse plants	Combines desirable traits from different parents	Time-consuming, unpredictable results
Genetic Engineering	Introducing specific genes into a plant	Precise trait modification, faster than conventional breeding	Regulatory hurdles, public concerns