Download Slides on Plant Breeding Methods Hybrid Crops | AGR 4321 and more Study notes Agricultural engineering in PDF only on Docsity! 1 Plant Breeding Methods Hybrid Crops. (S & P, Ch. 11) AGR 4321/5321 Plant Breeding/ Genetic Improvement of Plants Fall 2008 K. H. Quesenberry A. Some comments about hybrid cultivar development 1. The first generation offspring of a cross between inbred line parents with different genotypes. 2. Individuals in the cultivar are heterozygous, but the cultivar is homogenous. B. General procedures for hybrid cultivar development 1.Development of inbred lines 2.Crossing pairs of unrelated inbred lines 3.Producing seed of the single cross in commercial quantities at an affordable price. Introduction to Hybrids (1) C. Inbreeding in cross-pollinated crops 1. Definition – Any system of mating that leads to an increase in homozygosity. 2. Inbreeding depression (Shull 1906) 3. Characteristics of inbreds 4. Inbreeding effects on yield 5. Concept of hybrids and methods (Shull 1909, Jones 1918) Introduction to Hybrids (2) D. The Concept of Hybrid Vigor (1) 1. Definition – The increase in size, vigor, or productivity of a hybrid plant (also called heterosis) a. Superior to the mid-parent value b.Superior to either parent ** 2. Hybrid vigor may be reflected in various plant characteristics. 3. Hybrid vigor is generally greatest following crosses among diverse genotypes. 2. Explanations of hybrid vigor a. Favorable dominant genes – Alleles that contribute to vigor are dominant. Inbred A x Inbred B AABBccddEE aabbCCDDee F1 Hybrid AaBbCcDdEe b. Interaction of alleles at the same locus – Heterozygous superior to either homozygote (overdominance) D. The Concept of Hybrid Vigor (2) Commercial Utilization of Hybrids 1. Hybrid seed must be produced in sufficient quantity to supply grower demand at a reasonable price. 2. Easy in a monoecious plant like corn. 3. Accomplished by hand pollination in high value low seed requiring (per acre) horticultural crops like cucumber, pepper, and tomato. 4. CMS or chemical sterilization needed for large volume agronomic crops.
