1a. Objectives (from AD-416):
Hawaii’s solo papaya is the most delicious papaya in the world and has been adopted by numerous countries to develop their export papaya market. In particular, Brazil has used the Hawaiian solo ‘Sunrise’ papaya to develop a variety that has no blemishes or freckles that detract from the marketability, although it does not affect the taste quality of the papaya. In contrast, the solo papaya grown in Hawaii is the most delicious but suffers from blemishes that are referred to as ‘freckles’ (See Figures 1 and 2). In addition, Hawaii papaya needs to have resistance to the papaya ringspot virus which devastated Hawaii’s papaya in the 1990s. The development of the virus resistant ‘Rainbow’ and ‘SunUp’ papaya saved the papaya industry. In this proposal, we want to test market a Hawaiian solo papaya that is virus resistant in which we have incorporated the freckle free property from the Brazilian papaya described above. Success in this marketing proposal could be the ‘game changer’ for combining the delicious taste of the Hawaiian grown solo papaya with virus resistance and blemish free characteristics.
1b. Approach (from AD-416):
Fruits of the blemish free papaya were obtained from a Trader Joe’s market in California and seeds of the fruit were grown on the Hamakua coast of Hawaii; this line was designated N08-75. Fruit from those plants showed similar characteristics to the commercial variety and indeed were blemish free. The trees were self pollinated and harvested seeds were also grown in the Waiakea region of Hawaii Island that resemble the ‘lava’ type of soil and moisture conditions of Puna, where 90% of Hawaii’s papaya are grown. The resulting fruit of these trees were also free of freckles. To incorporate papaya ringspot virus-resistance to the line, the freckle papaya was crossed with ‘SunUp’, which is a papaya ringspot virus-resistant transgenic cultivar. Recipricol crosses were made using ‘SunUp’ and N08-75 and seeds of the cross were planted out in Waiakea and also in Puna at a commercial papaya farm. Fruit from these trees will become available in January 2013 and will serve as the basis of our marketing trials. In this proposal, the fruits will be harvested starting in 2013 and test marketed for: 1) degree of reduction in blemishes and maintenance of virus resistance, 2) taste quality, 3) brix (sugar) levels, 3) shelf life in local markets in which heat treatment of the papaya is not required, and 5) shelf life in export markets that require heat treatments by vapor heat or irradiation.
3. Progress Report:
This research is related to objective 2 on the inhouse project, "Strategically expand and improve current tropical/subtropical fruit and nut germplasm collections through international exchanges". Papaya plants from a cross of N08-75 x ‘SunUp’ and progeny from N08-75 and ‘SunUp’ self crosses are currently being grown at the ARS Waiakea experiment farm and commercial papaya farm in Hilo, Hawaii. Trees are being evaluated for fruit column (avoid plants with skips) and developing fruits will be evaluated for the fruit size and shape, number of freckles, and fruit quality. Fruit quality including number of freckles and Brix (total soluble sugar) are being compared to N08-75 and ‘SunUp’ fruits grown in the same field. In parallel, flowers of the hybrids are being bagged for self pollination and crossed with N08-75. We submitted an application to lease additional land to grow out papayas for evaluation and will use this land to evaluate additional F1 hybrids as well as the seeds from the selfed F1 fruits.