Crop Improvement Chapter VI

Crop Improvement Chapter VI

• Crop improvement involves methods to improve plant heredity for human benefit.
• The goal of plant breeding is to achieve higher yields.
• Gregor Mendel is considered the founder of genetics.
• His work established the fundamental laws of Mendelian inheritance.

Plant Breeding

• Plant breeding is the art and science of improving plant heredity for the benefit of humankind.

Chromosome and Gene

• Chromosome - a structural unit in the nucleus that carries genes in a linear and constant order, preserving its identity through cell generations. Chromosome number is usually consistent within a species.
• Gene - the unit of inheritance located on the chromosome; a segment of DNA that determines an amino acid sequence in a polypeptide.

Some Known Plant Breeders

• Glen W. Burton: A distinguished forage crop breeder for the US Department of Agriculture, known for improving pearl millet and developing turf grasses.
• Edgar E. Hartwig: A soybean breeder for the USDA, often referred to as "The Father of Soybeans in the South."
• Norman E. Borlaug: Awarded the 1970 Nobel Peace Prize for his contributions to peace and humanity through the breeding of high-yielding wheat; sometimes called "The Father of the Green Revolution."

International Breeding Centers

• AVRDC (Asian Vegetable Research and Development Center): Located in Shanhua, Taiwan, focusing on Chinese cabbage, mungbean, pepper, tomato, and soybean.
• ICARDA (International Center for Agricultural Research in the Dry Areas): Based in Aleppo, Syria, researching barley, chickpea, faba beans, tropical forages, and wheat.
• CIMMYT (International Maize and Wheat Improvement Center): Situated in Mexico, focusing on maize, triticale, and wheat.
• CIAT (International Center for Tropical Agriculture): Located in Cali, Colombia, investigating dry beans, cassava, rice, and tropical forages.
• ICRISAT (International Crops Research Institute for the Semi-Arid Tropics): Located in Patancheru, India, studying chickpea, millets, peanuts, pigeonpeas, and sorghum.
• IITA (International Institute of Tropical Agriculture): Located in Ibadan, Nigeria, focusing on cassava, cocoyam, cowpea, lima bean, maize, pigeon pea, rice, soybean, sweet potato, and winged bean yam.
• CIP (International Potato Center): Located in Lima, Peru, focusing on potatoes and sweet potatoes.
• IRRI (International Rice Research Institute): Located in Los Baños, Laguna, Philippines, focusing on rice.

Modern Plant Breeder Knowledge

• Botany - Taxonomy, morphology, reproduction of plants.
• Genetics and Cytogenetics - Mechanisms of heredity.
• Plant Physiology - Variety adaptation to their environment.
• Plant Pathology - Breeding for disease resistance.
• Entomology - Insect resistance.
• Plant Biochemistry - Suitability for industrial utilization.
• Statistics - Comparative performance of plant varieties.
• Agronomy - Understanding crops and their relative production.

Goals of Plant Breeders

• High yielding plants.
• Adaptability to different environments.
• Resistance to pests and diseases.
• Early maturing.
• Good storage qualities.
• Consumer preferences.
• Adapted to machinery.

Reproductive Processes of Plants

• Reproduction - the process by which plants produce offspring.
• Asexual Propagation:
  • Vegetative propagation; the production of offspring without the union of gametes.
  • Methods include: clones, root cuttings, stem cuttings, leaf cuttings, layering, grafting (side, tongue, cleft, splice).
• Sexual Propagation:
  • Uses seeds to create new plants.
  • Types of crosses include: single, double, three-way, top, multiple, back, crosses.

Methods of Crop Improvement

• Plant introduction
• Selection (mass & pedigree)
• Hybridization

Plant Introduction

• Obtaining superior varieties from other localities.
• Gathering diverse genotypes is the initial phase of a breeding program.

Selection (Mass and Pedigree)

• Criteria: Physical features, phenotype, yield, maturity.
• Mass Selection: Selecting and combining seeds from plants with desirable traits, no genetic tracing. Simpler but not as precise.
• Pedigree Selection: Method of selection which involves tracing desirable characteristics across generations, eliminating undesirable traits each generation until genetic purity is achieved. More precise than mass selection, but also more complex and time-consuming.

Clonal Selection

• Applies to vegetatively propagated plants.
• Selection of clones from a mixed population, based on phenotypic properties.

Hybridisation

• Combining traits from genetically distinct plants to produce a hybrid progeny.
• Types of Hybrid Crosses: single, double, three-way, top cross, multiple crosses, and backcross.