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  • Author or Editor: Francis 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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Seeds of the recalcitrant species lychee (Litchi chinénsis Sonn.) and longan (Dimocarpus longan Lour.) were stored near 100% relative humidity at 8 to 10C in air, 80% nitrous oxide (N2O) plus 20% oxygen, or 100% nitrous oxide. The combination of anesthetic and oxygen extended storage longevity of both species. Seeds stored in 100% N2O lost terminability at the same rate as those stored in air. Lychee seeds retained 92% of initial germination after 12 weeks under 80% N2O/20% O2, while those under air retained only 44%. Longan seeds failed to germinate after 7 weeks under air, yet retained 70% of their initial germination under 809” N2O/20% O2. The combination of anesthetic and oxygen atmospheres could provide a new approach to recalcitrant seed storage.

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Seeds of the recalcitrant species Litch i chinénis and Euphoria longan were stored in humid conditions at 8-10C under three different atmospheres: air, 80% nitrous oxide (N20)/20 % oxygen, and 100% nitrous oxide. The combination of anesthetic and oxygen extended storage longevity of both species. Oxygen was required for maintenance of viability; seeds stored under 100% N20 lost germinability at the most rapid rate. Lychee seeds retained 92% of control germination after 12 weeks under 80% N20/20% 02, while those under air lost 56% viability. Longan seeds lost all viability after 7 weeks under air, yet retained 70% of their control germination under 80% N20/20% 02. The combination of anesthetic and oxygen atmospheres could provide a new approach to recalcitrant seed storage.

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Abstract

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%.

Open Access

The year 2005 marked the 25th anniversary of the establishment of the U.S. Department of Agriculture (USDA) National Plant Germplasm System (NPGS), repositories devoted to clonally propagated, horticultural fruit and nut crops. During this quarter century, facilities in Hilo, Hawaii; Mayaguez, PR.; Miami, Fla.; and Riverside, Calif. were developed to preserve collections of tropical and subtropical fruit and nut crops; facilities in Brownwood, Texas; Corvallis, Ore.; Davis, Calif. and Geneva, N.Y. preserve the temperate crops. Each of these facilities now has internationally recognized, globally diverse collections of genetic resources for their assigned genera. Germplasm of unique genotypes are maintained as growing plants, evaluated for phenotypic and genotypic traits, documented in a national public germplasm database, and freely distributed as clonal propaggules to researchers and other germplasm users around the world. Seed collections represent wild populations for some crop relatives. These 8 genebanks maintain 30,000 accessions representing 1600 species of fruit and nut crops and their wild relatives. The genebanks distribute more than 15,000 accessions annually to international researchers. Although originally conceived as working collections for crop improvement, NPGS genebanks have also become invaluable in providing the raw materials for basic plant genetic research, reservoirs for rare or endangered species or vulnerable landraces, archives of historic cultivars, and field classrooms for educating the public. These collections preserve botanical treasures as well as the American horticultural heritage for now and for future generations.

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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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