Ebook Principles of plant genetics and breeding: Part 2
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Ebook Principles of plant genetics and breeding: Part 2
Section 6Classic methods of plant breedingChapter 16 Breeding self-pollinated species Chapter 17 Breeding cross-pollinated species Chapter 18 Breeding Ebook Principles of plant genetics and breeding: Part 2 g hybrid cultivarsMethods of breeding (or precisely, methods of selection) crops vary according to the natural method of reproduction of the species. Generally, there are two categories of breeding methods: those for self-pollinated species and those for cross-pollinated species. In practice, there Ebook Principles of plant genetics and breeding: Part 2 is no hard distinction between the two; breeders crossover and use methods as they find useful. Furthermore, plant breeders may use a combination of sEbook Principles of plant genetics and breeding: Part 2
everal methods in one breeding program, using one procedure at the beginning and switching to another along the way. It should be mentioned also that Section 6Classic methods of plant breedingChapter 16 Breeding self-pollinated species Chapter 17 Breeding cross-pollinated species Chapter 18 Breeding Ebook Principles of plant genetics and breeding: Part 2 er of plants to select, the number of generations to use, and other aspects of breeding, to suit factors such as budget and the nature of the trait being improved.16Breeding self-pollinated speciesPurpose and expected outcomesAs previously discussed, self-pollinated species have a genetic structure Ebook Principles of plant genetics and breeding: Part 2 that has implication in the choice of methods for their improvement, They arc naturally inbred and hence inbreeding to fix genet is one of the goals oEbook Principles of plant genetics and breeding: Part 2
f a breeding program for self-pollinated species in which variability is generated by crossing. However, crossing does not precede some breeding methoSection 6Classic methods of plant breedingChapter 16 Breeding self-pollinated species Chapter 17 Breeding cross-pollinated species Chapter 18 Breeding Ebook Principles of plant genetics and breeding: Part 2 udying this chapter, tire student should be able to discuss the characteristics, application,genetics, advantages, and disadvantages of the following methods ofselection:1Mass selection.2Pure-line selection3Pedigree selection.4Bulk population.5Single - seed desccn t.And to:6Describe die technique/mc Ebook Principles of plant genetics and breeding: Part 2 thod of backcrossing.7Discuss the method of multiline breeding.8Discuss the method of breeding composites.9Discuss the method of recurrent selection.TEbook Principles of plant genetics and breeding: Part 2
ypes of cultivarsAt the beginning of each project, the breeder should decide tin the type of cultivar to breed for release to producers. The breeding Section 6Classic methods of plant breedingChapter 16 Breeding self-pollinated species Chapter 17 Breeding cross-pollinated species Chapter 18 Breeding Ebook Principles of plant genetics and breeding: Part 2 e from four basic populations used in plant breeding- inbred pure lines, open-pollinated populations, hybrids, and clones. Plant breeders use a variety of methods and techniques to develop these cultivars.Ptite-llne cultivarsPure-line cultivars arc developed for species that arc highly self-pollinat Ebook Principles of plant genetics and breeding: Part 2 ed. These cultivars arc homogeneous and homozygous in genetic structure, a condition attained through a scries of self-pollinations. These cultivars aEbook Principles of plant genetics and breeding: Part 2
rc often used as parents in the production of other kinds of' cultivars. Pure-line cultivars have a narrow genetic base. They are desired in regions wSection 6Classic methods of plant breedingChapter 16 Breeding self-pollinated species Chapter 17 Breeding cross-pollinated species Chapter 18 Breeding Ebook Principles of plant genetics and breeding: Part 2 ltivars are developed for species that are naturally cross-pollinated. The cultivars are genetically heterogeneous and heterozygous. Two basic types of open-pollinated cultivars are developed. One type is developed by improving the general population by recurrent (or repeated) selection or bulking a Ebook Principles of plant genetics and breeding: Part 2 nd increasing material from selected superior inbred lines. The other type, called a synthetic cultivar, is derived from planned matings invoking seleEbook Principles of plant genetics and breeding: Part 2
cted genotypes. Open-pollinated cultivars have a broad generic base.Hybrid cultivarsHybrid cultivars are produced by crossing inbred lines that have bSection 6Classic methods of plant breedingChapter 16 Breeding self-pollinated species Chapter 17 Breeding cross-pollinated species Chapter 18 Breeding Ebook Principles of plant genetics and breeding: Part 2 ts the phenomenon of hybrid vigor (or heterosis) to produce superior yields. Heterosis is usually less important in crosses invoking self-pollinated species than in those involving cross-pollinated species. Hybrid cultivars arc homogeneous but highly heterozygous. Pollination is highly Controlled an Ebook Principles of plant genetics and breeding: Part 2 d restricted in hybrid breeding to only the designated pollen Source. In the past, physical human intervention was required to enforce this strict polEbook Principles of plant genetics and breeding: Part 2
lination requirement, making hybrid seed expensive. However, with time, various techniques have been developed to capitalize on natural reproductive cSection 6Classic methods of plant breedingChapter 16 Breeding self-pollinated species Chapter 17 Breeding cross-pollinated species Chapter 18 Breeding Ebook Principles of plant genetics and breeding: Part 2 rghum), because the natural reproductive mechanisms (e.g., cross-fertilization, cytoplasmic male sterility') are more readily economically exploitable than in self-pollinated species.Clonal cultivarsSeeds are used to produce most commercial crop plants. However, a significant number of species are p Ebook Principles of plant genetics and breeding: Part 2 ropagated by using plant parts other than seed (vegetative parts such as stems and roots). By using vegetative parts, the cultivar produced consists oEbook Principles of plant genetics and breeding: Part 2
f plants with identical genotypes and is homogeneous. However, the cultivar is genetically highly heterozygous. Some plant species sexually reproduce Section 6Classic methods of plant breedingChapter 16 Breeding self-pollinated species Chapter 17 Breeding cross-pollinated species Chapter 18 Breeding Ebook Principles of plant genetics and breeding: Part 2 d (i.e., the vigor is retained from one generation toanother), and then the improved cultivar propagated asexually. In seed-propagated hybrids, hybrid vigor is highest in the F|, but is reduced by 50% in each subsequent generation. In other words, whereas clonally propagated hybrid cultivars may Ik- Ebook Principles of plant genetics and breeding: Part 2 harvested and used for planting the next season’s crop without adverse effects, producers of sexually reproducing species using hybrid seed must obtaEbook Principles of plant genetics and breeding: Part 2
in a new supply of seed, as previously indicated.Apomictic cultivarsApomixis IS the phenomenon of the production of seed without the benefit of the unSection 6Classic methods of plant breedingChapter 16 Breeding self-pollinated species Chapter 17 Breeding cross-pollinated species Chapter 18 Breeding Ebook Principles of plant genetics and breeding: Part 2 as clonal cultivars). Hence, apomictic cultivars have the same benefits of clonally propagated ones, as previously discussed. In addition, they have the convenience of vegetative propagation through seed (versus propagation through cuttings or vegetative plant parts). Apomixis is common in perennial Ebook Principles of plant genetics and breeding: Part 2 forage grasses.MultilinesMultilines are developed for self-pollinating species. These cultivars consist of a mixture of specially developed genotypesEbook Principles of plant genetics and breeding: Part 2
called isolincs (or near isogenic lines) because they differ only in a single gene (or a defined set of genes). Isolines arc developed primarily for Section 6Classic methods of plant breedingChapter 16 Breeding self-pollinated species Chapter 17 Breeding cross-pollinated species Chapter 18 Breeding Ebook Principles of plant genetics and breeding: Part 2 the techniques of back-crossing in which the F| is repeatedly crossed to one of the parents (recurrent parent) that lacked the gene of interest (e.g., disease resistance).Genetic structure of cultivars and its implications Ebook Principles of plant genetics and breeding: Part 2 Section 6Classic methods of plant breedingChapter 16 Breeding self-pollinated species Chapter 17 Breeding cross-pollinated species Chapter 18 BreedingGọi ngay
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