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Genetics and Plant Breeding

Course developer

Prior knowledge

Biol1001, Botany

Biol3014, Plant Physiology I

LauZ2038, Basics in Agronomy I

Course abstract

The aim of the study course is to provide an in‑depth understanding of the fundamental principles of genetics as the theoretical basis for field‑crop breeding, as well as to acquire methods for the development and maintenance of cultivar types in various plant species. The course enables students to understand the mechanisms of heredity and variation, develop practical skills in breeding programme planning and evaluation of breeding material, and learn the basic principles of organising the breeding process. This course ensures that students are competent to participate in plant breeding and variety registration, and to apply the acquired knowledge in crop production and seed production.

Learning outcomes and their assessment

Knowledge of the fundamental principles of genetics and the essence of plant breeding, the interrelationship between these two fields, the main types of cultivars, their breeding schemes and methods, and the principles guiding the choice of these methods.

Skills and abilities in solving genetic tasks, as well as in preparing a breeding plan (selecting the appropriate breeding method and scheme depending on the characteristics of the plant species).

Students are competent to participate in the breeding processes of various field crop species. They are capable of defining breeding objectives and directions of specialization, planning breeding work, and evaluating breeding material. They are also competent to apply the acquired knowledge in crop production by selecting an appropriate cultivar type and carrying out seed production for it.
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Course Content(Calendar)

1. History of the Development of Genetics. Definition of genetics. Main fields of genetic research. Methods of genetic research. Stages in the history of genetics: Mendelism, the chromosomal theory of inheritance, development of molecular genetics. Genetics in Latvia. Genetics as the theoretical basis of plant breeding. (Lectures 1 h)
2. Cytological Basis of Heredity. Cell organelles and their role in heredity. Chromosomes, their types and structure. Mitosis and meiosis and their genetic significance. Plant reproduction: asexual and sexual reproduction. Types of pollination. Apomixis. (Lectures 1 h)
3. Molecular Basis of Heredity. Nucleic acids: DNA and RNA, their structure and functional differences. Replication, transcription, translation. The genetic code and its role in protein synthesis. Gene and its structure. Genome and its organization. Chromosomal theory of inheritance. Gene localization on chromosomes. Crossing-over, its types and frequency. Gene linkage. Genetic chromosome maps. Sex-linked inheritance. The role of gene recombination in plant breeding. (Lectures 2 h, Practical classes 2 h)
4. G. Mendel’s Laws of Inheritance. Essence of Mendel’s research methods. Genetic symbolism. Genotype and phenotype. Monohybrid crosses. Patterns of inheritance in monohybrid crosses. Test crosses and reciprocal crosses. Codominance, multiple allelism. Dihybrid and polyhybrid crosses. Independent assortment of traits. Conditions for the validity of Mendel’s laws. Gene interaction. Inheritance of traits resulting from non-allelic gene interaction. Inheritance of quantitative traits. Pleiotropy. Penetrance and gene expression. (Lectures 2 h, Practical classes 10 h)
5. Variability of Organisms. Non-heritable and heritable variability and mutations. Norm of reaction. Origin of mutations and their causes. Classification of mutations: gene, chromosomal, and genomic mutations. Mutagens, their classification and critical doses. N. Vavilov’s law of homologous series in hereditary variation. Use of different mutation types in breeding. Breeding schemes using mutants. Achievements in breeding mutant varieties of cereals, potatoes, legumes, grasses, and other crops. (Lectures 2 h, Practical classes 2 h)
6. Polyploidy. Concept of polyploidy. Haploid and diploid organisms. Polyploid series. Classification of polyploids: autopolyploids, allopolyploids, aneuploids. Main characteristics and regularities of polyploid plants and their importance in breeding. Development and characteristics of tetraploid and triploid crop varieties. Production of amphidiploids. Research on triticale development: hexaploid and octoploid triticale. Results of triticale breeding. Haploids and doubled haploids, methods of their production. Breeding schemes using haploids. Obtained varieties. (Lectures 2 h, Practical classes 2 h)
7. Interspecific bridization. Objectives and tasks. Incompatibility and methods of overcoming it. Methods to overcome sterility in the F1 generation. Wild species as donors of new traits in plant breeding and their use in breeding cereals, potatoes, and other crops. (Lectures 2 h).
8. Inbreeding and Heterosis. Inbreeding and its genetic basis in self-pollinated and cross-pollinated plants. Development and characteristics of self-pollinated lines and their use. Heterosis effect. Theories of the mechanism of heterosis. Scheme for producing heterotic hybrids: source material, development of inbred lines, their evaluation and determination of combining ability. Types of heterotic hybrids: variety–line hybrids, single-line, double-line, and three-line hybrids. Stages of developing F1 heterotic hybrid varieties. Non-chromosomal inheritance. Cytoplasmic inheritance organelles: plasmids and mitochondria. Discovery of cytoplasmic male sterility (CMS), its types and genetic basis. Characteristics of plants with CMS. Scheme for producing heterotic hybrids using CMS. CMS types in maize, rye, sugar beet, and other crops. Experience of CMS use in field crop breeding. Use of CMS in producing heterotic hybrids of various agricultural crops. (Lectures 2 h)
9. Population Genetics. Population and its role in nature. Hardy–Weinberg law and conditions for its validity. Breeding schemes for developing open pollinated varieties. (Lectures 2 h)
10. Concept of Breeding. Role of plant breeding. Directions and objectives of breeding: for specific agroecological regions, different vegetation periods, different utilization purposes, different levels of agricultural intensity, breeding for immunity and market requirements. Interaction of plant breeding with other sciences. Genetics as the theoretical basis of breeding. Choice of breeding methods depending on the mode of plant reproduction. Variety model and its importance in planning the breeding process. (Lectures 2 h, Practical classes 2 h)
11. Importance of Source Material in Plant Breeding. N. Vavilov’s theory of centers of origin of cultivated plants. Plant introduction: history and types. Genetic resources of agricultural plant species. Conservation in situ and ex situ. International Plant Genetic Resources Institute (IPGRI), its structure and functions. Gene banks: international, regional, national, and institutional. Types of crop collections: base, active, working, field, in vitro, and their importance in plant breeding. (Lectures 2 h)
12. Concept of a Variety. Definition of a variety, variety lifespan and influencing factors. Classification of varieties by origin: population varieties, local varieties, line varieties, clone varieties, hybrid varieties, heterotic hybrids. Types of genetically diverse varieties for organic agriculture. Variety model and concepts of its development. Morphological and physiological aspects of variety model creation. State variety testing, regulations for inclusion in State Variety Trials and decisions on testing results. DUS (Distinctness, Uniformity, Stability) test and VCU (Value for Cultivation and Use) test. Legislation on plant variety protection. (Lectures 2 h, Practical classes 8 h)
13. Intraspecific Hybridization. Plant emasculation and pollination. Principles of parent selection in hybridization. Concepts of varieties, traits, and genes. Types of crosses. Simple crosses: direct, reciprocal, diallel. Complex crosses: double, triple, stepwise, convergent, backcross. Characteristics of hybrid generations F1–F5. Methods for maintaining diversity in hybrid populations of self-pollinated plants. Bulk method: rationale and application, hybrid population size, selection opportunities, advantages and disadvantages. Pedigree system: rationale and essence, selection in early hybrid generations, variability potential, advantages. Breeding schemes for self-pollinated, cross-pollinated, and vegetatively propagated plants using hybridization. (Lectures 2 h, Practical classes 2 h)
14. Selection as a Breeding Method. Types of selection. Selection in populations of self-pollinated, cross-pollinated, and vegetatively propagated plants. Line, family, clone. Breeding objectives and selection background. Selection criteria: individual traits, trait complexes, variety model, various indices. Mass selection: single, repeated, continuous, positive, and negative. Individual selection in self-pollinated and cross-pollinated plant populations. Line selection. Simple family selection, individual family selection, group family selection, half-sib method. Genotype–environment interaction and its influence on breeding results. Breeding for various traits: disease resistance, resistance to unfavorable abiotic and biotic conditions, yield, and quality traits. (Lectures 2 h, Practical classes 2 h)
15. Main Stages and Organization of the Breeding Process. Creation of populations for selection. Selection of elite plants. Evaluation of progeny of elite plants. Main principles and methods of field trial design. Plot size, number of replications, arrangement of variants and replications, buffer zones. Phenological observations during the vegetation period. Sowing and harvesting regulations. Mechanization of the breeding process: seed preparation, sowing technology, cultivation and harvesting machinery, post-harvest seed processing. Documentation of the breeding process, labeling and storage of samples. (Lectures 2 h)
16. Genetic Markers. Phenotypic, biochemical, and DNA markers, their evaluation and application possibilities in plant breeding. Classification of DNA markers and methods of their development. Marker-assisted selection (MAS). (Lectures 2 h)

17. Modern Genetic Methods. Possibilities for accelerating the breeding process. Use of tissue culture in breeding. In vitro selection. Somaclonal variability. Genetic engineering, its possibilities and prospects in breeding. CRISPR-Cas genome editing. Gene synthesis. Production of recombinant DNA molecules, vectors. Gene cloning. Gene transfer into cells. GMOs, scientific and ethical aspects of their development and use. (Lectures 2 h, Practical classes 2 h)

Requirements for awarding credit points

Students are admitted to the examination only if they have successfully completed all required tests, written assignments, and have obtained a pass for seminar topics, as well as completed and received credit for all practical work scheduled in the course.

Description of the organization and tasks of students’ independent work

Students prepare for seminars on assigned topics, delivering oral presentations that integrate the knowledge acquired in the study course as well as information obtained from additional materials. They process and format the results of laboratory work and engage in preparation for tests and written assignments.

Criteria for Evaluating Learning Outcomes

Assessment of Learning Outcomes:
Students are required to complete eight tests on lecture topics, two written assignments covering the genetics and breeding sections, and one assignment on terminology. In addition, students must obtain a pass in seminar participation. The study course concludes with a final examination.
Requirements for Taking the Examination:
A positive assessment in all written assignments and the seminar pass is required for admission to the examination. If a student obtains a grade of seven or higher in all tests and written assignments, the final examination is awarded automatically.

Compulsory reading

1. Raipulis J. (2002) Ģenētikas pamati.- R.:Izdevniecība RaKa, 250 lpp.
2. Āboliņš M. Ģenētikas praktikums.- LLU., 1997.- 225 lpp.
3. Caligari P. An Introduction to Plant Breeding. Oxford: Blackwell Publishing. 2009. 209 p.
4. Plant Breeding. J.Brown., P.Caligari, H.Campos. Wiley Blackwell, 2014. 278 p. Nav LLU FB.

Further reading

1. Dictionary of Plant Breeding. Rolf H.J.Schlegel. CRC Press, 2010. 571 p. [tiešsaiste] [24.09.2019.] Pieejams: https://www.taylorfrancis.com/books/9780429150708
2. Chahal G.S., Gosal S.S. Principles and procedures of plant breeding. Harrow, U.K: Alpha Science International Ltd, 2002. 604. p.
3. Holms I. (1992) Laukaugu selekcija Latvijā.- R.: Avots, 112 lpp

Periodicals and other sources

1. Plant Breeding. Published by John Wiley and Sons. ISSN (printed): 0179-9541. ISSN (electronic): 1439-0523.
2. Euphytica Published by Springer. ISSN (printed): 0014-2336. ISSN (electronic): 1573-5060. Pieejams LLU FB abonētajā datubāze SpringerLink http://www.springerlink.com/content/0014-2336/

Notes

For the bachelor's study program of Agriculture, Faculty of Agriculture ,specialization in Agriculture.