Euphytica 132: 251–258, 2003. © 2003 Kluwer Academic Publishers. Printed in the Netherlands. 251 Variability in Namibian landraces of watermelon (Citrullus lanatus) Gillian L. Maggs-Kölling 1,2 & Jørgen L. Christiansen 2 1 National Botanical Research Institute, Ministry of Agriculture, Water and Rural Development, Private Bag 13184, Windhoek, Namibia, e-mail: gmk@mweb.com.na; 2 Department of Agricultural Sciences, The Royal Veterinary and Agricultural University, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark, e-mail: jlc@kvl.dk Received 8 March 2002; accepted 16 April 2003 Key words: morphology, seed weight, soluble solids, yield, yield components Summary An on-station experiment was carried out in northern Namibia to compare local landraces of watermelon to modern varieties. Three groups of local watermelon are distinguished by farmers in Namibia: watermelons for fresh con- sumption, cooking melons used for porridge, and seed melons for oil pressing. The present study was carried out to estimate agronomic potential of the local landraces and verify whether agronomic characteristics would justify the local groupings. Important agronomic and fruit-quality traits (yield, earliness, fruit weight, fruit number, rind thickness, soluble solids, seed weight, and tolerance to biotic and abiotic stress) were measured in seven landraces (three watermelons, three cooking melons and one seed melon) and compared to three modern cultivars frequently grown in Namibia. The study revealed that well-adapted, productive Citrullus lanatus landraces are available, and cultivated by local farmers throughout the northern regions of Namibia. Based on a combination of agronomic characteristics these local varieties could be grouped into three distinct types: watermelons, cooking melons, and seed melons, in agreement with farmers classification. Landrace water melons were characterized by smaller, less sweet fruits with larger seed and a thicker rind compared to modern varieties. Yield level was comparable but development was later and fruit number in some cases higher. Cooking water melons were less sweet than local water melon with large fruits comparable in size to modern cultivars. The only included seed watermelon had small fruits with large seeds and low soluble sugars. Yield varied from 118 t/ha for a giant cooking melon, out yielding all other accessions, to only 10t/ha for the seed melon type, but with considerable variation within groups. The earliness of commercial varieties may be of interest in developing a mixed portfolio of short- and long-cycle landraces, whereas plant vigour, resistance and seed characters in some of the Namibian landraces may be important traits for breeding for both local purposes and for commercial varieties. Introduction The species Citrullus lanatus (Thunb.) Matsum & Na- kai in the family Cucurbitaceae is indigenous to Nam- ibia, where distribution is widespread throughout the country (Launert & Rössler, 1968). Furthermore, the centre of origin of the cultivated form of watermelon is recognised to be the Kalahari Desert (Esquinas- Alcazar & Gulick, 1983). Watermelon is generally important as a cover crop in the intercropping farming systems of northern Namibia, where the cultivation of pearl millet (Pennisetum glaucum) is the main staple food crop (Matanyaire, 1996). World production of watermelon for 2000 was 62.887.643 t, while 3.355.835 t were produced in Africa during the same year (FAO, 2000). In addi- tion to the vast global production and consumption of traditional watermelon, farmers in northern Nam- ibia grow a range of C. lanatus landraces that are distinguished by fruit morphology, ecological require- ments and usage. This crop, adapted to the prevailing arid and unpredictable climatic conditions, provides an essential food source to supplement the nutrient- deficient, starchy, staple diet of subsistence farming communities. Unpublished ethnobotanical studies re- veal that this multipurpose local crop yields fruit flesh