Articles
STEPWISE PRIORITIES IN PAPAYA BREEDING
Article number
740_4
Pages
43 – 48
Language
English
Abstract
Systematic breeding for improvement of papaya varieties in Malaysia was started 36 years ago with the advent of the Malaysian Agricultural Research and Development Institute (MARDI). At the initial stage, priority was given on selection of baseline cultivars from farmers fields based on uniformity and yield. Baseline cultivars like Subang 6 and Batu Arang selected from this early program quickly helped to jumpstart the industry.
A follow-up breeding program puts emphasis on eating quality that was lacking in the early cultivars.
The backcross breeding program used the high quality, but less adaptable, Sunrise Solo as the recurrent parent in improving the eating quality of Subang 6. This led to the release of the Eksotika variety in 1987 and the start of a lucrative papaya export industry.
The Eksotika was very susceptible to fruit freckles and has orange-red flesh, and a subsequent breeding program was planned to improve the fruit cosmetics.
This was achieved in 1991 with the release of the Eksotika II which has more attractive, firmer flesh and much reduced fruit freckles.
The Eksotika II was a F1 hybrid between two sib lines, and it showed significant heterosis in yield.
In the five years following the release of Eksotika II, priorities in breeding shifted to development of F1 hybrids to exploit heterosis in yield and genetic buffering of hybrids in performance over varied environments.
The emphasis was on yield per unit area per unit time with stability in performance, rather than selection based on single tree yield, as practiced two decades earlier.
In wide crosses, heterosis in yield of hybrids was an astounding 199.6% over the better parent.
The results from the hybrid program convinced the industry that F1 hybrid varieties are far superior to self-pollinating pureline varieties. The outbreak of papaya ringspot virus disease in 1991 also saw a shift in emphasis to disease resistance breeding.
The donor parents for PRSV resistance genes were from Cariflora and Tainung 5. A mutation-breeding program using gamma irradiation was also initiated with similar goal of selecting resistant lines to PRSV. Currently selected hybrids are evaluated over several disease hotspots to establish their field resistance.
In 1996, biotechnology was brought in to help the industry in solving the PRSV threat as well as improving the shelf life of Eksotika papaya with delayed ripening characteristics.
Several genetically modified lines have since been evaluated in contained trials.
Future priorities may focus on breeding for designer papayas with increased nutritive values in vitamins and antioxidants as well as novelty in serving the fruit with minimal handling.
A follow-up breeding program puts emphasis on eating quality that was lacking in the early cultivars.
The backcross breeding program used the high quality, but less adaptable, Sunrise Solo as the recurrent parent in improving the eating quality of Subang 6. This led to the release of the Eksotika variety in 1987 and the start of a lucrative papaya export industry.
The Eksotika was very susceptible to fruit freckles and has orange-red flesh, and a subsequent breeding program was planned to improve the fruit cosmetics.
This was achieved in 1991 with the release of the Eksotika II which has more attractive, firmer flesh and much reduced fruit freckles.
The Eksotika II was a F1 hybrid between two sib lines, and it showed significant heterosis in yield.
In the five years following the release of Eksotika II, priorities in breeding shifted to development of F1 hybrids to exploit heterosis in yield and genetic buffering of hybrids in performance over varied environments.
The emphasis was on yield per unit area per unit time with stability in performance, rather than selection based on single tree yield, as practiced two decades earlier.
In wide crosses, heterosis in yield of hybrids was an astounding 199.6% over the better parent.
The results from the hybrid program convinced the industry that F1 hybrid varieties are far superior to self-pollinating pureline varieties. The outbreak of papaya ringspot virus disease in 1991 also saw a shift in emphasis to disease resistance breeding.
The donor parents for PRSV resistance genes were from Cariflora and Tainung 5. A mutation-breeding program using gamma irradiation was also initiated with similar goal of selecting resistant lines to PRSV. Currently selected hybrids are evaluated over several disease hotspots to establish their field resistance.
In 1996, biotechnology was brought in to help the industry in solving the PRSV threat as well as improving the shelf life of Eksotika papaya with delayed ripening characteristics.
Several genetically modified lines have since been evaluated in contained trials.
Future priorities may focus on breeding for designer papayas with increased nutritive values in vitamins and antioxidants as well as novelty in serving the fruit with minimal handling.
Publication
Authors
Y.K. Chan
Keywords
Carica papaya, papaya, breeding criteria, varieties, hybridization
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