Plant Breeding Concepts Quiz

Plant Breeding Principles and Methods

• Plant breeding is a science and an art of improving plants' genetic makeup for economic use.
• Plant breeding has been practiced for thousands of years and is considered a current phase of crop evolution.
• International development institutions believe plant breeding is essential for food security through higher yields, pest and disease resistance, drought resistance, and regional adaptation.
• Plant breeding is divided into three main areas: plant genetic resources (germplasm), breeding techniques, and seed production techniques.

Germplasm

• Germplasm is the total variability found in plant species, including cultivated and wild relatives.
• It encompasses collection, conservation, evaluation, documentation, and utilization of crop plants.

Breeding Techniques

• General breeding methods include introduction, selection, and hybridization (inter varietal).
• Special breeding techniques include mutation breeding, polyploidy, wide hybridization, and other specific techniques like tissue culture and genetic engineering for crop improvement.

Seed Production Techniques

• Seed production techniques primarily involve seed production principles and methods.

Objectives of Plant Breeding

• Increased yield through efficient genotypes.
• Improved quality (e.g., milling, cooking quality, aroma, grain colour, gluten content, protein content; reducing toxic substances).
• Resistance to biotic and abiotic stresses (e.g., pests, diseases, drought, soil factors, edaphic).
• Improved agronomic characteristics (e.g., plant height, branching).

Centres of Origin

• Vavilov, a prominent botanist, proposed the concept of centres of origin in which crop plants evolved from wild species.
• These areas of diversity are critical for new crop development and offer significant genetic diversity for breeding and improvement.

History of Plant Breeding in India

• Organized agricultural research in India started in 1871.
• The Indian Council of Agricultural Research (ICAR) was established in 1929.
• Many crop-specific commodity committees were established (e.g., cotton, jute, sugarcane).
• Important research activities have been carried out by ICAR and affiliated institutes.
• Agricultural universities were established across India in the early 20th century, leading to progress in agricultural research.

Activities in Plant Breeding

• Creation of variations: The first step of developing new crop varieties involve creation of variations. Methods includes domestication, germplasm collection, plant introduction, hybridization, mutation, polyploidy, and genetic engineering.
• Selection: Plants with desired traits and characteristics are identified and selections are done. This process of selection is carried out based on phenotype.
• Evaluation: Traits are evaluated in several conditions or locations by comparing them to established variety.
• Multiplication: The seed of the selected cultivar, if a new variety is ready for release is produced on larger scale.
• Distribution: The appropriate seed multiplication agencies sell certified seeds to the farmers.

Modes of Reproduction and Pollination

• Sexual Reproduction: Involves the fusion of male and female gametes.
• Asexual Reproduction: Multiplication of plants without sexual fusion.
• Pollination: Transfer of pollen to female stigma. This includes: Autogamy (self-pollination), and Allogamy (cross-pollination).

Methods of Breeding Self-Pollinated Crops

• Pure line selection
• Mass selection.
• Single seed descent method.

Methods of Breeding Cross-Pollinated Crops

• Recurrent selection
• Backcrossing
• Top cross
• Hybridisation

Polyploidy Breeding

• Euploidy: involves whole sets of chromosomes.
• Aneuploidy: a numerical change in a chromosome.
• Polyploidy results in changes in the genetic makeup of the organism leading to variations or creating new varieties.
• Common methods of polyploidy breeding include Colchicine treatment and in vitro culture.

Wide Hybridization

• Wide hybridization is the crossing of plants from different species or genera.
• It is a significant method of transferring desirable genes from wild relatives to cultivated crops.
• Techniques such as: direct hybridization, chromosome doubling, use of pollen mixtures etc.

Molecular Markers

• Molecular markers assist in identifying, characterizing, and mapping genes in plants.
• Examples include RFLP, RAPD, STS, AFLP.

Genetic Theories

• Dominance Hypothesis: Heterosis is due to masking of deleterious recessive traits in heterozygotes.
• Overdominance Hypothesis: Superiority of heterozygotes is due to the production of novel products or gene interaction that provides better performance.

Heterosis Breeding

• Heterosis breeding focuses on creating hybrids with improved traits compared to their parental inbred lines.
• Methods include: top cross, single cross, three-way cross and double cross.

Mutation Breeding

• Mutation breeding introduces changes in the genetic material to generate variation for desirable traits.
• Chemical mutagens and physical mutagens can be used in the mutation process.

In Vitro Selection

• In vitro selection involves selecting desired varieties in a controlled environment, outside the plant.
• Applicable to plants in which asexual reproduction is the primary method of reproduction, like potato, sugarcane, etc.

Characteristics of Pure Lines & Mass Selection

• Purelines: Uniformly similar genotypes.
• Mass Selection: Selection of superior plants from a mixed population with similar phenotypes.