![]() Several other sources of resistance to gummy stem blight in melon have been reported over the years ( McGrath et al., 1993 Sakata et al., 2000 Sowell, 1981 Takada, 1983 Tsutsumi and da Silva, 2004 Zhang et al., 1997). Furthermore, resistance in plant introduction 140471 has recently been described as variable ( Tsutsumi and da Silva, 2004) or not effective at all ( Takada, 1983). (1993) contends no sufficient resistance to GSB is available in melon. (1966) tested over 1000 accessions of melon and reported resistance in plant introduction 140471 to be near immunity. A limited amount of resistance was reported in some cultigens. Several greenhouse, plastic tunnel, and field evaluations were previously conducted to identify sources of resistance to D. Use of resistant cultivars is the most strategic, environmentally friendly, accepted, and economic means of GSB management ( Vokalounakis, 1993 1995 Wehner and St. This illustrates the necessity to use host resistance in conjunction with good cultural practices and judicial use of fungicides. Crop rotations are only partially effective wind and other agents can easily bring in new inoculum to start new infections ( Tullu et al., 2002). bryoniae from several cucurbit production areas has been reported ( Kato et al., 1984 Keinath and Zitter, 1998 Malathrokis and Vokalounakis, 1983). Moreover, development of resistance to some systemic benzimidazole fungicides in D. The disease has also been reported in Europe ( Frantz and Jahn, 2004 van Steekelenburg, 1985), Asia ( Wako et al., 2002), and elsewhere ( Bruton, 1998).Īlthough chemical control has had great success, repeated use of fungicides is not advisable as a long-term solution as a result of the negative impact of pesticides in the environment. Amand and Wehner, 1991) and on watermelon ( Citrullus Neck.) ( Keinath et al., 1995). The pathogen attacks and inflicts heavy losses in quality and yield in several other genera of the cuburbitaceae worldwide, e.g., squash ( Cucurbita L.) ( Zitter and Kyle, 1992), cucumber ( Cucumis L.) in the United States ( Gusmini and Wehner, 2002 St. Of these pathogens, Didymella bryoniae (Auersw), Rehm that causes gummy stem blight (GSB) is one of the most destructive resulting in substantial economic losses ( Bruton, 1998 Crosby et al., 2002 Frantz and Jahn, 2004 McCreight, 2002 Wako et al., 2002). Melon production is severely constrained by several soil-borne disease pathogens. gummy stem blight disease resistance inheritance single dominant gene Analysis of segregation of F 1, F 2, and backcross generations of the three crosses indicated that each of the three plant introductions carry a single dominant gene for resistance to the D. We also identified other sources of resistance not reported previously, for example, JF1 a wild Cucumis from the highlands of Kenya was rated highly resistant. This plant introduction that was considered resistant was highly susceptible in our study. However, some plant introductions identified as highly resistant elsewhere were susceptible under our conditions, the most interesting being plant introduction 482399. Results of germplasm screening indicated most germplasms reported as resistant elsewhere were confirmed resistant under our conditions. bryoniae at the four to six true-leaf stages and assessed for leaf and stem damage at 7, 14, and 21 d postinoculation. Seedlings in both studies were inoculated with a spore suspension (5 × 10 5 spores/mL −1) of D. Six populations of each cross (susceptible parent, resistant parent, F 1, F 2, the two reciprocal backcrosses) were analyzed for their responses to D. bryoniae was studied in three crosses between plant introductions 157076, 420145, and 323498, resistant parents that were fairly adapted (flowering, fruiting, powdery mildew tolerance) to Nanjing conditions, and plant introductions 268227, 136170, and NSL 30032 susceptible parents, respectively. Two hundred sources of germplasm (plant introduction accessions, cultivars, breeding lines, landraces, and wild relatives) were screened against a single highly virulent isolate (IS25) of D. bryoniae and to characterize the genetics of resistance in the resistant accessions. The objectives of the present study were to critically evaluate melon ( Cucumis melo L.) germplasm for resistance to D. Gummy stem blight incited by the fungus Didymella bryoniae is a major disease of melons worldwide.
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