Genetics with the Fundamentals of Breeding - M.P. Myhun - 2008

Chapter VIII. Genetic Foundations of Breeding

8.4. Creation of Initial Material for Breeding

Genetic Water/126.html">Diversity of the initial material serves as the foundation for developing new plant varieties and animal breeds. All types of genotypic Variability—both recombinational and mutational, including chromosomal and genomic Mutations—are of great importance.

Therefore, all measures aimed at expanding the range of variability in plants and animals help generate A wide variety of parental forms from which the most promising ones can be selected.

The sources of initial material can include natural PLANT AND ANIMAL forms, folk-selected varieties and breeds, previously developed varieties and breeds, wild forms of both related and other species, as well as plant collections (Gene pools) from the VIR and the Yuryev Institute of Ukraine. Today, Introduction/32.html">Genetic Engineering and cellular technologies play a crucial role in creating initial material for breeding.

Combinative variability plays a significant role as a source of initial material. The range of variability in existing plant and animal forms can be substantially expanded through intraspecific Hybridization. Understanding the inheritance patterns of individual traits and properties enables the breeder to use hybridization to purposefully combine the properties required for a future variety in a single genotype, discard genotypes with undesirable traits, and obtain homozygous forms.

Utilizing combinative variability can not only help obtain initial material for further breeding but also serve as a direct method for developing new breeds and varieties.

An important source of combinative variability is distant hybridization. In certain cases, the latter makes it possible to combine The properties of systematically distant forms. N.V. Tsitsin obtained wheat-couch grass hybrids and, on their basis, developed wheat varieties that retained fragments of the couch grass genome along with such valuable properties as perennial growth and lodging resistance. Intergeneric hybridization in breeding was utilized by G.K. Meister, A.R. Zhebrak, A.O. Sapehin, and O.I. Shulindin.

Mutational variability. Mutations constitute the primary source of hereditary variability as well. Therefore, artificial control over the mutation process and the enhancement of its quantitative and qualitative efficiency are crucial prerequisites for expanding the scope and obtaining qualitatively new initial material for breeding. The primary supplier of initial

material for breeding is induced mutagenesis, triggered by ionizing radiation, ultraviolet rays, and especially Chemical Mutagens. Through artificial mutagenesis, hundreds of agricultural crop varieties and microorganism strains have been created worldwide. Chemical compounds have been used to induce mutations in mammals, such as changes in rabbit coat and eye color. Well-known are the theoretical developments by I.A. Rapoport and others regarding The Use of chemical mutagenesis in plant breeding. The first radiation mutants of wheat in Ukraine were obtained by A.O. Sapehin, L.N. Delone, and V.I. Didus. Induced mutagenesis is used with particular success in microorganism breeding. Valuable initial material for breeding can also be obtained through genomic mutations. Aneuploid plant forms (monosomics and nullisomics) can be used to analyze the allelic composition of linkage groups or to substitute a specific chromosome with a chromosome from another variety; however, haploid and polyploid plant forms are of significantly greater importance. Polyploid forms form The basis of many economically valuable forms and varieties.

When obtaining initial material for breeding, the potential of polyploid forms is frequently combined with the advantages of combinative variability.

For practical breeding purposes, both generative and somatic mutations are utilized. The latter can play a decisive role in the breeding of organisms that reproduce primarily vegetatively (clonal Selection).