SABRAO Journal of Breeding and Genetics 35(1) 19-26, 2003 NEW SOURCE OF RESISTANCE TO CUCUMBER MOSAIC VIRUS IN MELON B.S. DARYONO 1, 2 *, S. SOMOWIYARJO 3 , and K.T. NATSUAKI 1 SUMMARY Forty melon cultivars collected from 17 Asian countries were screened for resistance to an Indonesian isolate of Cucumber mosaic virus (CMV-B2) by manual inoculation and examined by enzyme-linked immunosorbent assay (ELISA). Resistance to this virus was found in 5 cultivars (Yamatouri, Miyamauri, Mawatauri, Sanuki-shirouri, and Shinjong). Furthermore, to study the inheritance of resistance to CMV-B2, the resistant Yamatouri cultivar was crossed with the susceptible cultivar, Vakharman. In the F 1 , F 2 and reciprocal backcross populations, resistance to CMV-B2 was demonstrated to be conferred by a single dominant gene to which the symbol Creb-2 was assigned. Key words: inheritance, ELISA, CMV, Cucumis melo L. Melon (Cucumis melo L.) is a valuable cash crop grown throughout the world. It is a cross-pollinated diploid (2n = 2x = 24) species of African origin and a member of the family Cucurbitaceae (Wang et al., 1997). This is a large group of plants with about 90 genera and over 700 species largely confined to warmer climates (Robinson and Walters, 1999). Commercial melon production in Indonesia has been significantly increasing over the last decade (DARI, 2000). While the demand for high-quality melon products increased, the commercial production of melon has been increasingly hampered by virus or virus-like diseases showing mosaic and other symptoms. Cucumber mosaic virus (CMV) is a member of the genus Cucumovirus, and is one of the common viruses attacking cucurbits, having a larger host range than most viruses (Smith et al., 1988). Aphids transmit CMV in a non- persistent manner (Palukaitis, 1992). CMV is also one of the most agronomically-important viruses in Indonesia as it causes considerable losses in CMV-infected melon and other cucurbit plants (Somowiyarjo et al., 1993). This virus frequently causes substantial loss in yield and inferior fruit quality, especially in the early melon seeding. Since no chemical pesticides have been effective in limiting the incidence of the virus, the use of genetic resistance against this virus is a possible control strategy (Khertapal et al., 1998). There have been some reports of CMV resistance in melon germplasm. However, the genetics of resistance has been determined only in the cultivars ‘Freeman’s Cucumber’ (Karchi et al., 1975), ‘Mi tang ting’, and ‘Shirouri-nigo’ (Takada, 1979). Resistance in the cultivars ‘Freeman’s Cucumber’ and ‘Shirouri-nigo’ was conferred by three recessive genes (Karchi et al., 1975 and Takada, 1979), while two recessive genes conferred it in the cultivar ‘Mi tang ting’ (Takada, 1979). However, classification of inheritance patterns and transfer of resistance from sources have been complicated by isolate specificity and may be 1 Lab. of Tropical Plant Protection, Department of International Agricultural Development, Tokyo Univ. of Agriculture, Setagaya-ku, Tokyo 156-8502, Japan., Tel: +81-3-5477-2412 Fax: +81-3 5477-4032; 2 Lab. of Genetics, Faculty of Biology, Gadjah Mada University, Yogyakarta 55281, Indonesia; 3 Lab. of Plant Virology, Faculty of Agriculture, Gadjah Mada University, Yogyakarta 55281, Indonesia. * Corresponding author: bud.daryono@lycos.com. 19