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Disease Note.

First Report on the Identification of Races 0, 1, and 1,2 of Fusarium oxysporum f. sp. melonis in Lebanon. Y. Abou-Jawdah, Faculty of Agricultural and Food Sciences, American University of Beirut, Beirut, Lebanon . A. M. Al-Khoury, Faculty of Agricultural and Food Sciences, American University of Beirut, Beirut, Lebanon. Plant Dis. 80:711. Accepted for publication 10 April 1996. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-0711C.

Muskmelon (Cucumis melo L.) wilt, incited by Fusarium oxysporum Schlechtend.:Fr. f. sp. melonis Leach & Curr, causes severe losses in the main muskmelon production areas in Lebanon. In 1993 and 1994, muskmelon plants showing wilt symptoms were collected from locations where the disease was most prevalent. The pathogen was isolated and identified as F. oxysporum f. sp. melonis. Monoconidial cultures were prepared for each isolate. Three differential cultivars of muskmelon were used in virulence tests for race identifiaction according to the system suggested by Risser et al. (1): Ananas Kareem Hybrid F1, which lacks specific resistance genes, and Romeo Hybrid F1, and Griffalia F1, carrying the resistance genes Fom 1 and Fom 2, respectively. A fourth cultivar, N 14.37 F1, claimed to have a polygenic or horizontal resistance to races of F. oxysporum f. sp. melonis, including Fom 1 and Fom 2, was also included. Seedlings, 10- to 14-day-old, at the first true-leaf stage were inoculated by the root dip method (2) in spore suspensions (l06 conidia ml -1) prepared from 7- to 13-day-old cultures. The virulence tests were conducted twice. The results indicated the presence of races 0, 1, and 1,2. Race 2 was not detected. N14.37 F1, was tolerant to some isolates of race 1,2 and susceptible to others, suggesting the existence of two pathotypes within race 1,2. However, this observation requires further investigation

References: (1) G. Risser el al. Phytopathology 66:1105, 1976. (2) F. W. Zink et al Plant Dis. 67:1251, 1983.