PRODUCTION OF F1 HYBRID PAPAYA SEED IN MALAYSIA

Abstract

The ‘Frangi’ papaya is a F1 hybrid developed by the Malaysian Agrifood Corporation Berhad (MAFC) from hybridization between 2 inbred parents ‘LSGC1’ and ‘LSGC2’. The seed production plot is located at Lanchang, Pahang which is about 100 km east of Kuala Lumpur. This so called ‘Lanchang Seed Garden’ occupies an area of 1 ha and in May 2007, 1800 trees of ‘LSGC1’ and 600 trees of ‘LSGC2’ inbred parents were planted. The trees flowered two months later and hybridization work was then started. Freshly dehisced anthers from ‘LSGC2’ (paternal parent) hermaphrodite flowers were collected in glass vials and used for pollination of ‘LSGC1’ (maternal parent) flowers. The recipient flower must be mature, but the corolla tube must remain folded to prevent accidental outcrossing. To effect pollination, the closed petals of the recipient female flower are gently separated to expose the stigma. One anther is picked up from the vial with a pair of curved-tipped forceps and gently rubbed onto the stigma of the ‘LSGC1’ flower. A wax paper envelope is then placed over the pollinated flower. Both female and hermaphrodite flowers of ‘LSGC1’ were used for hybridization and in the latter, emasculation by peeling off the corolla tube with its attached stamens is necessary to prevent self-pollination. Female flowers used in hybridization have the advantage of obviating emasculation and the fruit carries more seed compared with hermaphrodite, but its seed will bear a higher percentage of female trees that is not usually preferred. Reciprocal crosses using ‘LSGC2’ as maternal parent were also experimented with. ‘LSGC1’ as maternal parent produced fruit that was nearly twice the weight of ‘LSGC2’ and concomitantly the seed number per fruit was also doubled (245 vs. 121 seed). However, ‘LSGC2’ yielded 50% more fruit than ‘LSGC1’ and this accounted for a net 36% higher seed based on per tree basis. Over 18 months, ‘LSGC1’ and ‘LSGC2’ produced 15,042 and 20,510 seeds/tree, respectively. Field trials of F1 hybrids from direct and reciprocal crosses showed that there were no significant differences in performance. Hence, ‘Frangi’ seed production currently uses a 2-way cross. Seed harvest began in December, 2007 and rose to a peak of 90 kg in February, 2009. The trees after 18 months were too tall for hybridization and the seed garden was replanted after two years of seed production.