Novel food information: Human food use of virus resistant papaya line 55-1

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Health Canada has notified the Papaya Administrative Committee of Hawaii that is has no objection to the food use of papaya cultivars 'Rainbow' and 'SunUp', which are derivatives of the genetically modified papaya line designated 55-1. This line has been developed to express the coat protein of papaya ringspot virus (PRSV) which confers resistance to infection by the virus. The Department conducted a comprehensive assessment of this virus resistant papaya according to the Guidelines for the Safety Assessment of Novel Foods (September 1994). These Guidelines are based upon internationally accepted principles for establishing the safety of foods with novel traits.

The following provides a summary regarding the Papaya Administrative Committee of Hawaii's notification to Health Canada and contains no confidential business information.


A virus resistant papaya line has been developed which expresses the coat protein of papaya ringspot virus (PRSV) conferring resistance to infection by this virus. The PRSV virus is a viral pathogen belonging to the potyvirus group of plant viruses and is considered the major limiting factor in commercial papaya production throughout the world.

Development of the modified plant

The Papaya Administrative Committee of Hawaii has provided information characterizing the process used in developing papaya line 55-1. The modification was a result of using particle mediated transformation which introduced a DNA construct into papaya plant cells. The plasmid construct consisted of the neomycin phosphotransferase II (NPTII), -glucuronidase (GUS), and papaya ringspot virus coat protein (PRSV CP) gene coding sequences and the regulatory components necessary for expression.

The PRSV CP gene is derived from the papaya ringspot virus strain PRSV HA 5-1. The plant expression of the viral coat protein confers the ability to resist the PRSV. The GUS gene is derived from Escherichia coli and the NPTII gene was originally obtained from the Tn5 transposon. Both genes are commonly used as a selectable marker for transformed cells. Molecular and inheritance analysis indicates that line 55-1 contains the PRSV CP gene and the NPTII and GUS plant-expressible marker genes at one integration site in the papaya genome.

The novel phenotype is stably incorporated into papaya line 55-1 and is expressed as expected. The genetic modification results in the addition of the novel PRSV CP, NPTII, and GUS gene sequences in the genome of papaya line 55-1and the expression of three novel proteins (PRSV CP, NPTII, and GUS).

Product information

Papaya is a tropical fruit that has edible flesh and seeds. The fruit is grown commercially in many tropical areas including Brazil, Chile, Indonesia, India, Mexico. In the United States, papayas are cultivated in Hawaii and Florida. Hawaiian varieties are the papayas commonly found in supermarkets. However, susceptibility of the papaya fruit to PRSV has limited production.

Virus resistant papaya differs from its traditional counterpart in the expression of three novel proteins (PRSV CP, NPTII, and GUS).

Dietary exposure

Papaya consumption is considered to be minor in Canada, although there are subgroups in the Canadian population that consume the fruit in higher amounts. Papaya is not relied upon as a staple food in Canada. Virus resistant papaya line 55-1 is expected to be used in similar applications as other papaya varieties by the food industry.


The data submitted included analytical results for total soluble solids, carotenoids (-carotene, -carotene, -cryptoxanthin, total carotenoids), vitamin C, and minerals (potassium, phosphorus, calcium, magnesium, sodium, iron, copper, zinc, boron) for line 55-1. The results from the compositional analysis of 55-1 were within the range of levels found in non-transgenic cultivars grown in Hawaii.

Toxicology data

The PRSV coat protein is not considered to be novel with respect to human consumption since fruit infected with PRSV has commonly been consumed apparently without adverse effect. Naturally occurring infections of papaya result in concentrations of coat proteins at much higher levels than those expressed in papaya line 55-1. The proteins used as marker genes have been previously evaluated for toxicological safety as they are commonly used as marker genes in genetically modified plants.


Health Canada's review of the information presented in support of the food use of virus resistant papaya line 55-1, concluded that this line does not present human food safety concerns. Health Canada is of the opinion that virus resistant papaya is as safe and nutritious as currently available commercial papaya varieties. Health Canada's opinion pertains only to the food use of virus resistant papaya line 55-1.

This Novel Food Information document has been prepared to summarize the opinion regarding the subject product provided by the Food Directorate, Health Products and Food Branch, Health Canada. This opinion is based upon the comprehensive review of information submitted by the petitioner according to the Guidelines for the Safety Assessment of Novel Foods (September 1994).

For further information, please contact:

Novel Foods Section
Food Directorate
Health Products and Food Branch
Health Canada, PL2204A1
251 Frederick Banting Driveway
Ottawa, Ontario K1A 0K9

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