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  • Author or Editor: Francis T. Zee x
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Sterile distilled water was found to be an acceptable medium for the maintenance of tissue-cultured plantlets of three Ananas accessions. Eighty-one percent of the plantlets survived 12 months at 25C in 1 ml of sterile distilled water. Plantlets stored in water for 12 months were observed to be more vigorous than those that were cultured for 12 months in full-strength Murashige and Skoog (MS) medium. However, medium containing l/4-strength MS salts and full-strength organics, 3% sucrose, and agar gave the best plant survival and vigor. None of the plantlets in this study produced callus. Only a single instance of axillary budbreak was observed in explants stored on the l/4-strength MS medium.

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Viable larvae of the Oriental fruit fly (Dacus dorsalis Hendel) were found in Carica papaya L. ‘Kapoho’ fruit after hot water double-dip quarantine treatment in Hawaii. Two types of blossom end defects, navel and definite pinhole, were responsible for the failure of the quarantine treatment. These defects resulted from abnormal placental growth near the blossom end of fruit. Defective fruit also had higher incidences of internal infection by Cladosporium sp. and Fusarium spp. A survey conducted in the Puna district of the island of Hawaii showed that the incidence of trees bearing defective fruit ranged from 5.3% to 31%.

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Papaya ringspot virus (PRSV) is a devastating disease that has a detrimental impact on both commercial papaya production and Caricaceae germplasm conservation. In 1998, the PRSV coat protein transgenic line 55-1 and derived progeny were released to growers in Hawaii. The transgenic varieties have provided durable and practical control of the disease that have saved the papaya industry. However, like with transgenic crops throughout the world, there is public concern about the possibility of cross-contamination of these transgenic materials into nontransgenic lines. As the designated germplasm repository for Caricaceae, we are responsible for maintaining the genetic integrity of each accession. Therefore, we have developed a protocol using polymerase chain reaction for detection of the adventitious presence of the 55-1 transgene insertion event in both parental plants and their progeny seed populations. This protocol assures a 99.9% confidence level of obtaining seeds that are 99.5% transgene-free. The protocol developed in this study is not typical for most seed validation techniques because there is a higher than normal producer risk resulting from the potential of large numbers of seeds not meeting the stringent criteria. However, we believe this is necessary to ensure the genetic integrity of seeds stored in the repository.

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