Principles of Plant Breeding (2+1)

Introduction

• Self-pollination is considered the highest degree of inbreeding a plant can achieve. It promotes homozygosityof all gene loci and traits of the sporophyte. To be classified as self-pollinated, cross-pollination should notexceed 5%. Due to self pollination further, the progeny of a single plant ishomogeneous due to self pollination. A population of self-pollinated species, comprises a mixture of homozygous lines.
• Self-pollination restricts the creation of new gene combinations (no introgression of new genes throughhybridization). New genes may arise through mutation,but such a change is restricted to individual lines orthe progenies of the mutant plant. The proportions of different genotypes, not the presence of newly introducedtypes, define the variability in a self-pollinated species.
• Because a self-pollinated cultivar is generally one single genotype reproducing itself, breeding self-pollinated species usually entails identifying one superior genotype (or a few) and its multiplication it. Specificbreeding methods commonly used for self-pollinated species are pure-line selection, pedigree breeding, bulkpopulations, and backcross breeding Table: Examples of predominately self pollinated crops