<p style="text-align: justify;"><b>Field Testing</b></p>

<p style="text-align: justify;">The transgenic papaya lines 55-1 and 63-1 were field tested in the United States (1991 through 1996). Extensive testing of papaya lines 55-1 and 63-1 in laboratory, greenhouse, and field experiments, determined that the plants exhibited the typical agronomic characteristics of the parent papaya variety &lsquo;Sunset&rsquo;, with the addition of resistance to PRSV infection. The variation in agronomic characteristics did not differ significantly from that seen in commercial cultivars of papaya. Field trial reports demonstrated that the transformed papaya lines 55-1 and 63-1 had no effect on nontarget organisms or the general environment.</p>

<p style="text-align: justify;"><b>Outcrossing</b></p>

<p style="text-align: justify;">Papaya (<i>Carica papaya</i> L.) plants have different mating systems and may be either dioecious (staminate and pistillate plants) or gynodioecious (hermaphrodite and pistillate plants). Commercial papaya lines are mostly gynodioecious lines and are preferred because of their potential for inbreeding and consequent uniformity. The hermaphroditic plants are generally self-pollinating due to the position of the anthers relative to the stigma such that in commercial production self-pollination occurs without manual assistance or bagging. A low rate of out-crossing still occurs since hermaphrodites tend to produce copious pollen from staminate flowers during most of the year. Additionally, the pistillate plants never produce anthers and are consequently obligate out-crossers. In nature, pollination of papaya occurs through bees, butterflies, and wind.</p>

<p style="text-align: justify;">Papaya is usually described as sexually incompatible with other member of the Carica genus. Initial steps have been taken to develop methods for somatic hybridization of <i>C. papaya</i> with <i>C. stipulata</i> and with <i>C. pubescens</i>, but no hybrid plants have been regenerated to date.</p>

<p style="text-align: justify;">Papaya is the best known member of the Caricaceae, a small dicotyledonous family consisting of four genera. Carica is the largest genus with 23 described species with overlapping distributions in the foothills of the Andes Mountains in northwestern South America, although members of the genus range from southern Brazil, Argentina and Chile to southern Mexico. Most likely, the center of origin for papaya is the Caribbean coast of Central America. United States commercial production of papaya is generally in Hawaii with secondary production in Puerto Rico and southern Florida.</p>

<p style="text-align: justify;"><b>Weediness</b></p>

<p style="text-align: justify;">No Carica species is considered a weed, and there is no evidence in the scientific literature to suggest that susceptibility to PRSV is the factor that prevents these plants from being weed pests. Therefore, it seems likely that even if the PRSV-resistance trait could be transferred from line 55-1 or 63-1 to another Carica species, the resultant offspring would not be weed pests.</p>

<p style="text-align: justify;"><b>Secondary and Non-Target Adverse Effects</b></p>

<p style="text-align: justify;">It was concluded that the genes inserted into the transgenic papaya lines 55-1 and 63-1 would not result in any deleterious effects or significant impacts on nontarget organisms, including threatened and endangered species or beneficial organisms. The PRSV coat protein expressed in these papaya lines is found in all PRSV-infected plants, and there are no reports of this protein having any toxic effects. In fact, this viral coat protein is routinely ingested by virtually all animals, including humans, when papaya is consumed. Naturally occurring infections of susceptible papaya varieties result in concentrations of coat proteins far higher than those that occur in the tissues of the transgenic papaya lines 55-1 and 63-1. No direct pathogenic properties, nor any hypothetical mechanisms for pathogenesis toward beneficial organisms, such as bees and earthworms, were identified for papaya lines 55-1 and 63-1.</p>
