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Siriyan R.,Si Sa Ket Horticultural Research Center | Sompak S.,Si Sa Ket Horticultural Research Center | Nimkingrat T.,Si Sa Ket Horticultural Research Center | Khumcha U.,Nong Khai Agricultural Research | Chaikiattiyos S.,Horticultural Research Institute
Acta Horticulturae

The Department of Agriculture (DOA), Ministry of Agriculture and Cooperatives, Thailand has conducted papaya breeding since 1984. These programs were divided into two types, conventional breeding and genetic engineering. Conventional breeding included selection and crossing of papayas. Seeds were collected from various sources, planted and selected for desired characteristics. They were self-pollinated to increase the purity of the lines. The DOA recognized and registered 'Khaek Dam Si Sa Ket' cultivar in 1994. With regard to cross breeding, 'Khaek Dam' cultivar was crossed with 'Coimbatore No.2' ('Co2') cultivar. The cross bred seeds were selected from the F1 hybrid papaya. The DOA named this fruit 'Phichit' and it became a registered cultivar in 1997. There is also a cross between the 'Khaek Dam' and the 'Florida Tolerant'. From this program, new cultivars, 'Khaek Dam Tha Phra' and 'Khon Kaen 80' were selected based on good agricultural traits and then the 'Khaek Dam Tha Phra' was registered in 1997. On the other hand, the genetic engineering improvement under the DOA was in collaboration with Cornell University. The coat protein gene (CP gene) of Papaya ringspot virus (PRSV) was transferred into Thai papaya, 'Khaek Dam' and 'Khaek Nuan' cultivars. Potential resistant cultivars were selected for the R0 PRSV of the resistant papaya, including one 'Khaek Dam' and four 'Khaek Nuan' cultivars. Currently, one 'Khaek Dam' and two 'Khaek Nuan' cultivars are selected for the R3 PRSV resistant papaya. Source

Sompak S.,Si Sa Ket Horticultural Research Center | Siriyan R.,Si Sa Ket Horticultural Research Center | Nimkingrat T.,Si Sa Ket Horticultural Research Center | Chaikiattiyos S.,Horticultural Research Institute | Khumcha U.,Nong Khai Agricultural Research and Development Center
Acta Horticulturae

Papaya (Carica papaya) is one of the major fruit crops of Thailand and is consumed as both green and ripe fruit. There are some phenotypic variations found amongst commercial cultivars that can be used as a resource for genetic improvement. The objectives of this study were to collect, conserve and characterize papaya germplasm grown at Si Sa Ket Horticultural Research Center, Si Sa Ket, Thailand. Twenty cultivars of papaya were collected and morphological data recorded following IPGRI's papaya descriptors, including tree height, stem color, mature leaf petiole color, shape of mature leaf, fruit shape, fruit skin color, fruit flesh color, shape of central cavity, flavors, average fruit weight, etc. The results show that tree heights at the stage of the first floral opening ranged between 68-255 cm. Stem colors were mostly greenish, 'Khon Kaen 80' and 'Hawaii' had a grayish-brown stem color, only 'Hinan' had a purple stem color. Colors of mature leaf petiole were mainly pale green, only 'Hinan' and 'Si Thong' had reddish-purple and pale yellow leaf petioles, respectively. There were three types of mature leaf teeth - straight convex and concave. Fruit shapes from hermaphrodite flowers can be divided into six types, lengthened-cylindrical, elongated, pear, club, reniform and oval shaped. Skin and flesh colors of the ripe fruit vary from orangish-green to reddish-orange. Central cavity spaces were round, angular, slightly star and starshaped. Total soluble solids (TSS) of the ripe fruits ranged from 10 to 16°Brix. The average fruit weight was between 1-2 kg. The characteristic data recorded of each cultivar are basic information and will be used for further papaya research and development in Thailand. Source

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