Abstract
Papaya ringspot virus (PRSV) continues to be the limiting factor to production of papaya in most areas of the world. Pathogen-derived resistance has been used to successfully develop PRSV resistant 'Sunset' papaya expressing the translatable coat protein (CP) gene of PRSV HA 5-1 from Hawaii. Tests showed that the 55-1 transgenic line, later named 'Sun Up', was highly resistant under field conditions in Hawaii. Here we report on transgenic 'Sunrise' papaya expressing the untranslatable CP gene of PRSV HA 5-1. A key modification for improving transformation efficiency was to spread somatic embryos onto filter paper on induction medium, allowing them to grow for 4 weeks and spreading them again, 3 days prior to bombardment. Spreading allowed the synchronous development of small, rapidly growing embryos at the time of bombardment. Nine bombarded plates produced 207 kanamycin resistant clusters over a period of 7 months. Eighty-three of these clusters produced transgenic plant lines. Of these lines 25 were resistant to the homologous PRSV isolate from Hawaii and some of these were also resistant to PRSV isolates outside of Hawaii, including Australia, Taiwan, Mexico, Jamaica, Bahamas and Brazil. The spreading technique has been successfully applied by other workers in the laboratory to transform papaya with other CP genes.
Published Version
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