Self-pollinated varieties
The most popular variety of papaya in the world today is the Solo. It is so called because of its small fruit, about 350 500g each, which is convenient as a single serving. Within this variety are many lines such as Line 5, Line 8, Line 10, Kapoho, Waimanalo and Sunrise . Kapoho is the major cultivar in Hawaii while Sunrise which is the only pink-flesh line, is widely grown in many parts of the world.
Cross-pollinated varieties
Dioecious varieties such as Hortus Gold, Sunnybank, Betty and Cariflora, which have male and female flowers on separate trees, are enforced cross-pollinators. Hortus Gold from South Africa , Sunnybank ( Australia ) and Betty ( Florida , USA ) are very old varieties. The female fruits are yellow-fleshed and typically round. Cariflora fruits are also yellow fleshed, but smaller and quite tolerant to the ringspot virus disease. There are also gynodioecious varieties that are cross-pollinated such as Khaek Dam, Maradol, Cibinong and Cavite . Khaek Dam is Thailand 's best known variety . It is vigorous, bears red-fleshed fruit about 1.2 kg with 10.6% total soluble solids content. Maradol originates from Cuba , is a short-stature variety that bears fruit very close to the ground. The fruit weighs 1-2 kg, is attractive with firm red flesh with 10-11 % total soluble solids content. It has a characteristic musky flavour. The fruit is quite susceptible to anthracnose . Cibinong is an Indonesian variety with large red-fleshed fruit (2-3 kg) and grown mainly for its high papain yield. Cavite or Pineras is a Philippine variety with large, oblong fruit weighing 1.5 6 kg and thick, yellow to orange flesh.
Hybrids
Commercial F1 hybrids of papaya are rare. An important hybrid developed in Taiwan that has resistance to papaya ringspot virus disease is Tainung no. 5 which was developed from a cross between Florida (FL-77-5) and the Costa Rica Red.
Hybrid papaya varieties appear to show better adaptability, vigour and yield performance over traditional cultivars and they are expected to be more important in the future.
Clonal varieties
Honey Gold is perhaps the only known papaya clone in the world today. It is a dioecious variety from South Africa which was selected and propagated from generation to generation by leafy cuttings. Clonal varieties have the advantage of greater uniformity, especially in fruit shape, which is sex-linked. Clonally propagated Honey Gold gives fairly high yields of 25 - 30 t/ha year under subtropical conditions and has been known to remain productive for 10 or more years.
Vasconella (Carica) pentagona or Babaco, which is grown to a small extent in Ecuador and New Zealand is also exclusively clonally propagated by cuttings because of its parthenocarpic fruits.
Transgenic varieties
The world's first transgenic papaya was SunUp, which was transformed with coat-protein mediated resistance to papaya ringspot virus disease. Rainbow is the first transgenic commercial variety developed in Hawaii from a cross between SunUp and the conventional cultivar Kapoho. Transgenic varieties of Kamiya have also been developed by introduction of the coat-protein transgene from Rainbow through convention hybridisation and backcrossing.
Transgenic papaya varieties with delayed fruit ripening and resistance to papaya ringspot virus disease are currently being actively developed in Malaysia, Thailand, Indonesia, Philippines and Vietnam under the Papaya Biotechnology Network of Southeast Asia. |