Breeding of Vegetable, Spice and Tuber crops (2+1)

Hybridization

• During the 20th century, planned hybridization between carefully selected parents has become dominant in the breeding of self-pollinated species.
• The object of hybridization is to combine desirable genes found in two or more different varieties and to produce pure-breeding progeny superior in many respects to the parental types.
• Genes, however, are always in the company of other genes in a collection called a genotype.
• The plant breeder’s problem is largely one of efficiently managing the enormous number of genotypes that occur in the generations following hybridization.
• As an example of the power of hybridization in creating variability, a cross between hypothetical wheat varieties differing by only 21 genes is capable of producing more than 10,000,000,000 different genotypes in the second generation. At spacing normally used by farmers, more than 50,000,000 acres would be required to grow a population large enough to permit every genotype to occur in its expected frequency.
• While the great majority of these second generation genotypes are hybrid (heterozygous) for one or more traits, it is statistically possible that 2,097,152 different pure-breeding (homozygous) genotypes can occur, each potentially a new pure-line variety.
• These numbers illustrate the importance of efficient techniques in managing hybrid populations, for which purpose, the pedigree procedure is most widely used