Gone Global: Familiar and Exotic Cucurbits Having Asian Origins

Cucurbits are a group of diverse horticultural species grown worldwide. Their fruit are consumed fresh, cooked, or processed, and seeds can be eaten or used for their high quality cooking oil and protein meal. India and Southeast Asia, including China, comprise the primary and secondary centers of diversity, respectively, of cucumber (Cucumis sativus L.). India and central and southwest Asia comprise the primary center of diversity for melon (Cucumis melo L.), with China as a secondary center. Watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai var. lanatus] is important throughout Asia, although its primary center of diversity is west and central Africa. European forms of melon, cucumber and watermelon were introduced to the New World multiple times. Asian varieties of these and other cucurbits [e.g., bitter (Momordica charantia L.) and luffa (Luffa cylindrical L.) gourds] have been introduced to the U.S from the late 1800s to the present. Sustainability and improvement of U.S. melon, cucumber, and watermelon varieties have been achieved through introgression of genes from their respective Asian germplasm pools for disease and pest resistance, increased genetic diversity, productivity, and quality. Resistance to Podosphaera xanthii (Castagne) Braun & Shishkoff was first found in two Indian melons. Three types of resistance to melon aphid (Aphis gossypii Glover) were found in melons from India and Korea. Cucumis hystrix from China was crossed with cucumber to create the amphidiploid (Cucumis hytivusChen and Kirkbride) through which novel genetic variation was introgressed to cucumber. Gynoecious sex expression in cucumber was derived from Japan. Asian watermelon accessions may be the source for canary yellow flesh, which adds unique nutritional and flavor content to our diet. Technological advancement and genetic improvement pioneered in Asia advanced cucurbit production worldwide. Research on the feasibility of seedless watermelon was initiated in Japan in the late 1920s. Today, seedless types account for a major share of the watermelon market. Grafting, which originated in Asia in 1920s, using disease- and pest-resistant, or cold tolerant rootstocks is essential for sustainable cucurbit production in many parts of the world, and holds great potential as an alternative to methyl bromide fumigation. For example, interspecific hybrids of Cucurbita maxima Duch. and Cucurbita moschata Duch. ex Poir., two New World species, are the most widely used rootstock for cucurbits in Japan and South Korea, and Indian bottle gourd (Lagenaria siceraria L.) introductions of Indian origin are valuable sources of germplasm for breeding multiple disease resistant rootstocks.