Why Some Papaya Plants Fail to Fruit

Papaya fruits may fall from the plant when about golf-ball size due to lack of pollination of a female flower. The distinction between female and hermaphrodite papaya plants is described. With “solo” papaya cultivars, allowing three seedlings to develop in each planting site gives a 96 percent chance that selection for a single hermaphrodite plant will be possible

Sensitivity of a real-time PCR method for the detection of transgenes in a mixture of transgenic and non-transgenic seeds of papaya (\u3cem\u3eCarica papaya\u3c/em\u3e L.)

Background Genetically engineered (GE) ringspot virus-resistant papaya cultivars ‘Rainbow’ and ‘SunUp’ have been grown in Hawai’i for over 10 years. In Hawai’i, the introduction of GE papayas into regions where non-GE cultivars are grown and where feral non-GE papayas exist have been accompanied with concerns associated with transgene flow. Of particular concern is the possibility of transgenic seeds being found in non-GE papaya fruits via cross-pollination. Development of high-throughput methods to reliably detect the adventitious presence of such transgenic material would benefit both the scientific and regulatory communities. Results We assessed the accuracy of using conventional qualitative polymerase chain reaction (PCR) as well as real-time PCR-based assays to quantify the presence of transgenic DNA from bulk samples of non-GE papaya seeds. In this study, an optimized method of extracting high quality DNA from dry seeds of papaya was standardized. A reliable, sensitive real-time PCR method for detecting and quantifying viral coat protein (cp) transgenes in bulk seed samples utilizing the endogenous papain gene is presented. Quantification range was from 0.01 to 100 ng/μl of GE-papaya DNA template with a detection limit as low as 0.01% (10 pg). To test this system, we simulated transgene flow using known quantities of GE and non-GE DNA and determined that 0.038% (38 pg) GE papaya DNA could be detected using real-time PCR. We also validated this system by extracting DNA from known ratios of GE seeds to non-GE seeds of papaya followed by real-time PCR detection and observed a reliable detection limit of 0.4%. Conclusions This method for the quick and sensitive detection of transgenes in bulked papaya seed lots using conventional as well as real-time PCR-based methods will benefit numerous stakeholders. In particular, this method could be utilized to screen selected fruits from maternal non-GE papaya trees in Hawai’i for the presence of transgenic seed at typical regulatory threshold levels. Incorporation of subtle differences in primers and probes for variations in cp worldwide should allow this method to be utilized elsewhere when and if deregulation of transgenic papaya occurs

Sensitivity of a real-time PCR method for the detection of transgenes in a mixture of transgenic and non-transgenic seeds of papaya (Carica papaya L.)

BACKGROUND: Genetically engineered (GE) ringspot virus-resistant papaya cultivars ‘Rainbow’ and ‘SunUp’ have been grown in Hawai’i for over 10 years. In Hawai’i, the introduction of GE papayas into regions where non-GE cultivars are grown and where feral non-GE papayas exist have been accompanied with concerns associated with transgene flow. Of particular concern is the possibility of transgenic seeds being found in non-GE papaya fruits via cross-pollination. Development of high-throughput methods to reliably detect the adventitious presence of such transgenic material would benefit both the scientific and regulatory communities. RESULTS: We assessed the accuracy of using conventional qualitative polymerase chain reaction (PCR) as well as real-time PCR-based assays to quantify the presence of transgenic DNA from bulk samples of non-GE papaya seeds. In this study, an optimized method of extracting high quality DNA from dry seeds of papaya was standardized. A reliable, sensitive real-time PCR method for detecting and quantifying viral coat protein (cp) transgenes in bulk seed samples utilizing the endogenous papain gene is presented. Quantification range was from 0.01 to 100 ng/μl of GE-papaya DNA template with a detection limit as low as 0.01% (10 pg). To test this system, we simulated transgene flow using known quantities of GE and non-GE DNA and determined that 0.038% (38 pg) GE papaya DNA could be detected using real-time PCR. We also validated this system by extracting DNA from known ratios of GE seeds to non-GE seeds of papaya followed by real-time PCR detection and observed a reliable detection limit of 0.4%. CONCLUSIONS: This method for the quick and sensitive detection of transgenes in bulked papaya seed lots using conventional as well as real-time PCR-based methods will benefit numerous stakeholders. In particular, this method could be utilized to screen selected fruits from maternal non-GE papaya trees in Hawai’i for the presence of transgenic seed at typical regulatory threshold levels. Incorporation of subtle differences in primers and probes for variations in cp worldwide should allow this method to be utilized elsewhere when and if deregulation of transgenic papaya occurs

Is Organic Papaya Production in Hawaii Threatened by Cross-Pollination with Genetically Engineered Varieties?

The organic certification regulations of the USDA currently define “organic” foods to exclude “genetically engineered” crop varieties. In Hawaii, the genetically engineered papaya varieties ‘Rainbow’ and ‘SunUp’ were released in 1998 to provide protection from a damaging disease, papaya ringspot virus, which threatened to destroy the papaya industry. The rapid adoption of these varieties on about half of the total production acreage in Hawaii has caused concern among growers of organic papayas, who fear that uncontrolled pollination of their plants by genetically engineered papayas in the vicinity will make their fruits unmarketable as organic produce. This publication provides pertinent information for growers who want to continue to produce organic papayas in regions where genetically engineered trees are common

Crop Improvement by Conventional Breeding or Genetic Engineering: How Different Are They?

Conventional breeding and genetic engineering are different but complementary ways of improving crops, and either can be appropriate or inappropriate in particular cases, depending on the breeding objectives. Although neither improvement strategy is totally without risk, the potential for a poor choice of target gene makes regulatory oversight important and obligatory during the development of transgenic crops through genetic engineering

UH Rainbow' Papaya--A High-quality Hybrid with Genetically Engineered Disease Resistance

A transformed papaya cultivar combining the superior quality of Hawai‘i’s “solo” papayas with resistance to papaya ringspot virus is briefly described, and questions about genetic engineering are addressed

Update on Genetically Engineered PRV Resistance

Initial efforts to genetically engineer resistance to papaya ringspot virus are described, and the regulatory environment is briefly reviewed

Genetic Diversity in Eastern Polynesian Eumusa Bananas

Genetic variation within and between the Polynesian Eumusa bananas from Hawai'i, the Marquesas, and the Society Islands is described. Morphological, isozymic, ethnographic, and linguistic-assessments of accessions are used to identify base clones and somatic mutants. A historical review of relevant studies is summarized

Geographic Survey of Genetic Variation in Kava (Piper methysticum Forst. f. and P. wichmannii C. DC.)

A survey of the genetic resources of kava (Piper methysticum Forst. f. and P. wichmannii C. DC.) was conducted throughout the Pacific. Leaf tissues of more than 300 accessions, collected on 35 islands, were analyzed for isozyme variation in eight enzyme systems including ACO, ALD, DIA, IDH, MDH, ME, PGI, and PGM. Isozymes in P. methysticum cultivars from Polynesia and Micronesia were monomorphic for all enzyme systems examined; however, cultivars from Melanesia were polymorphic for ACO, DIA, MDH, and PGM. The genetic base of this crop is much narrower than previous morphological and biochemical studies suggest. Most of the morphotypes and chemotypes apparently originated through human selection and preservation of somatic mutations in a small number of original clones. Isozymes of P. wichmannii confirmed its status as the wild progenitor of kava. Piper methysticum cultivars and P. wichmannii and P. gibbilimbum C. DC. wild forms were all found to be decaploids with 2n = lOx = 130 chromosomes, but there was no firm evidence that interspecific hybridization has played a role in the origin of P. methysticum