BREEDING OF SEED AND VEGETATIVELY PROPAGATED TROPICAL FRUITS USING PAPAYA AND PINEAPPLE AS EXAMPLES
The first step at the start of a breeding programme is to establish the germplasm or collection of varieties to provide breeders with the basic resource. After evaluation, characterization and documentation, the collection becomes the genetic inventory from which breeders can draw out accessions that can become 'baseline' varieties for immediate recommendation or to be used as parents for hybridization and improvement of existing commercial varieties. The breeding strategies for papaya and pineapple are very different. For pineapple, the main strategy is to identify and select the most promising progeny or progenies and perpetuate them by asexual means. The heterozygous genetic make up of the selection is then fixed and its fidelity in performance is repeated from generation to generation. Hence, clonal populations can be expected to be very uniform. The success in selection of improved clones depends on the genetic variation and it may be necessary in the case of pineapple, to generate variation through hybridization. Hybridization between heterozygous pineapple parents result in F1 with a wide spectrum of segregating recombinants. These segregating progenies will provide a rich genetic resource for selection of improved varieties. The papaya is normally seed-propagated. The genetic uniformity of papaya is achieved either by self-pollination of hermaphrodite varieties to achieve homozygozity in which case the varieties are purelines or inbreds, or by hybridization of homozygous lines in which case the varieties are heterozygous F1 hybrids. F1 hybrid papaya varieties are better than purelines because their heterozygosity ensures better genetic buffering against environmental stress and they also exhibit heterosis in yield. Non-disclosure of inbred parents guarantees protection and exclusivity in the production of hybrid seed. The success in development and release of improved papaya and pineapple varieties at the Malaysian Agricultural Research and Development Institute are highlighted. New hybrids like the improved storage 'Eksotika' papaya and the Maspine pineapple have been accepted for commercial cultivation by the Malaysian Agrifood Corporation. The future breeding strategies including breeding for disease resistance, addressing requirements of industrial and pharmaceutical markets and finding novel ways to conveniently serve the papaya and pineapple for ubiquitous consumption are also discussed.
Chan, Y.K. (2008). BREEDING OF SEED AND VEGETATIVELY PROPAGATED TROPICAL FRUITS USING PAPAYA AND PINEAPPLE AS EXAMPLES. Acta Hortic. 787, 69-76
hybridization, heterozygous, homozygous, germplasm collection, hermaphrodites