Cucurbit Genetics Cooperative Report 19:66-67 (article 24) 1996
Breeding and Production of Watermelon for Edible Seed in China
Melon Research Institute, Gansu University of Agriculture, Lanzhou, Gansu, 730070, P.R. China
Introduction: Edible seed watermelon had been grown in China for several hundred years, mainly as a source of edible seed. This is the same species as common watermelon grown for flesh (Citrullus lanatus (Thunb.) Matsum and Nakai). The area under cultivation is increasing, up to 140,000 ha with seed yields of over 200,000 t, as the economy develops and demand for seed to be exported increases. Edible seed watermelon is grown mainly in the provinces of Gansu, Xingjiang, Neimen, Ningxia, and Anhui, and is a very important economic crop in China.
Varieties and Type: Cultivated edible seed watermelon are divided into two classes: those with large black seeds, and those with red seeds. The edge of the large black-seeded type is black with a white center. Commercially, it is most desirable that the black and white sectors are sharply contrasted. Seed width is the important measure and is used as the standard for seed size, with narrower seeds bringing less profit than wider seeds. Be foe 1989, seed width was less than 10 mm, and seed yield was less than 1,500 kg/ha/ After 1989, breeders, using various selection techniques, developed varieties with an increased seed width to approximately 11 mm. Over two to three years the larger-seeded varieties progressively replaced the smaller-seeded varieties, and yields increased to about 2,250 kg/ha. Representative varieties are 'GN-1' and 'Jingyuan Daban'.
There are also varieties that are used for both flesh and seeds. In traditional Chinese medicine the flesh has been found to be good for the stomach, and in the edible seed production area, many people eat the flesh of these watermelons. The flesh of most edible seed varieties is poor, with soluble solids between 4 and 5%. However, there are varieties bred for both flesh and edible seeds, with soluble solids between 6 and 7%, the flavor is good, and the seed width is about 10 mm. A representative variety is 'Lahzhou Daban'. The skin of the fruit is thick and the flesh is pliable so there is little water loss and fruits can be preserved until November or December. The flesh has a distinctive flavor when eaten in winter.
Red-seeded edible seed varieties are cultivated over much less area than black-seeded varieties. The seed color is completely red and the width is about 8 mm. A representative variety is 'Ningxia Red'.
Seeds: In recent years, breeders have used larger red-seeded varieties grown for flesh, and crossed them to large black-seeded edible seed lines, and developed new lines through selection and inbreeding. These new strains have a seed width of about 10 mm, and their production has been well received in the expanding watermelon market.
Problems: Though there are many large black-seeded edible seed watermelon varieties, most are closely related, and they all are very susceptible to anthracnose, powdery mildew, and other diseases. The problem is that there are few larger-seeded edible seed accessions in the available watermelon germplasm. When edible seed varieties are crossed with disease-resistant varieties developed for flesh, the progeny have smaller seed and lower seed yield than is desirable. It has proven to be very difficult to breed varieties for disease-resistance and high seed yield.
Red-seeded varieties of edible seed watermelon are welcome in commerce, but they have only 50 to 75% of the yield of black-seeded varieties. The problem is that the inheritance of seed color is complicated, with three genes r (red), t (tan), and w (white) interacting, and black-dotted seeds dominant over all three genes. Thus, if you cross red seed with any other seed color, the F1seeds are not red. It is difficult to breed for large-seeded, high-yielding, red-seeded edible seed varieties.
The key to solving these problems is to find germplasm with desirable characteristics that can be used either directly or indirectly in edible seed watermelon breeding programs.
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