Cohen, R., Agricultural Research Organization, Institute of Plant Protection, Newe Ya'ar Research Center, Ramat Yishay, Israel
Burger, Y., Agricultural Research Organization, Institute of Plant Sciences, Newe Ya'ar Research Center, Ramat Yishay, Israel
Horev, C., Agricultural Research Organization, Institute of Plant Protection, Newe Ya'ar Research Center, Ramat Yishay, Israel
Saar, U., Agricultural Research Organization, Institute of Plant Sciences, Newe Ya'ar Research Center, Ramat Yishay, Israel
Raviv, M., Agricultural Research Organization, Institute of Plant Sciences, Newe Ya'ar Research Center, Ramat Yishay, Israel

The effect of peat moss on fusarium wilt of melon (Cucumis melo L.) was studied in order to improve the selection process of resistant melons during breeding programmes. Disease symptoms were evident earlier and disease progress was faster in seedlings that were transplanted to peat following inoculation than in those transplanted to sand. The resistant breeding line used as a control did not show any wilt symptoms in either medium. Mixing the peat with sand or perlite reduced the disease development rate and the final disease incidence. The effects of peat and sand on disease progress were evaluated with two segregating melon populations in which the expected susceptible : resistant ratio was 25 : 75. In both populations, disease incidence was higher in the peat, which enables breeders to identify resistant plants and to lower the risk of using escapees as resistant plants. The mechanism of disease enhancement may include both biotic and abiotic components. There is an indication that peat induces plant susceptibility before inoculation. Melon seedlings germinated in peat and transplanted into sand exhibited significantly greater wilt incidence than those that germinated in sand and were transplanted into sand following the inoculation. Disease progress in sterile peat was significantly slower than that in non-sterile peat, which suggests the possible involvement of microbial activity.