GENETIC ALTERATION ASSOCIATED WITH FRUIT DOMESTICATION

Domestication of fruits involves a combination of genetic events including species selection; the recurrent selection of unique, elite, clones and vegetative propagation. These are combined with the development of horticultural technology such as irrigation in dry climates, pruning and training, pollination, harvesting, storage, and processing techniques. Genetic changes associated with domestication of fruits include the breakdown of dioecy, loss of self-incompatability, induction of parthenocarpy and seedlessness, polyploidy and allopolyploidy, loss of toxic substances, ease of vegetative propagation, and loss of spines, thorns, or pubescence. Other changes due to selection include increase in fruit size, increase in sugar content, and increase in storage and shelf life. Factors contributing to genetic improvement include interspecific recombination, polyploidization though unreduced games, and continued mass selection involving generations of sexual recombinants. Currant progress has been achieved through intensification of the same forces that have occurred during domestication with emphasis on increased adaptability through hardiness, chilling requirements, and photoperiod insensitivity, resistance to biotic stress, plant architectural modifications, and selection for color mutations. Molecular techniques hold out the promise of increasing the efficiency of selection through molecular markers and insertion of individual genes through transgene technology.