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Antifungal activity in aqueous and organic extracts from Momordica charantia and Momordica balsamina were evaluated against three pathogens: Fusarium oxysporum f. sp. melonis, Macrophomina phaseolina, and Alternaria solani. Cold-water extracts of 12 Momordica accessions exhibited various degrees of inhibition of the three pathogens: A. solani was more suppressed by the different extracts than F. oxysporum or M. phaseolina. Extracts from accessions 5 and 10 from M. balsamina were the most effective at inhibiting the tested fungi. Accession 10 exhibited the highest suppression level, more than 30% higher inhibition relative to the untreated control. Heating the cold extracts resulted in loss of antifungal activity in all cases. Hot ethanol extracts of the studied accessions exhibited a somewhat different pattern: F. oxysporum and M. phaseolina were strongly inhibited relative to A. solani. Interestingly, accession 10, which excelled in its inhibitory activity in the cold-water extract, was not effective whe...

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.

Grafted watermelon is a combination of two plants, aCucurbita rootstock and a watermelon scion. Therefore, weed control for this crop faces a unique problem: the safety of the selected herbicide has to be tested for both plants that make up the grafted plant. In the current study, we evaluated the usage safety of selected herbicides forCucurbita rootstocks as well as for non-grafted and grafted watermelons, and the control ofAmaranthus retroflexus by the same herbicides. In addition, the residual effect of the herbicides was tested for seeded and transplanted melons representing the next crop following cultivation of the grafted watermelons. The herbicides ethalfluralin, pendimethalin, ethalfluralin, sulfentrazone, oxyfluorfen, chlorsulfuron and clomazone were chosen for their potential to controlA. retroflexus. Pendimethalin and trifluralin were less effective than the other herbicides in controllingA. retroflexus; sulfentrazone, chlorsulfuron and clomazone were not safe for use on the tested cucurbits and thus cannot be recommended for weed control in grafted watermelons. Therefore, by eliminating the herbicides that are toxic to cucurbits and those that are ineffective forA. retroflexus control, it was concluded that the herbicides ethalfluralin and oxyfluorfen can be considered effective and safe for weed control in grafted watermelons. It was shown that trifluralin and oxyfluorfen have the potential to be applied effectively through the drip irrigation system.

SummarySuccess in grafting depends on the identification of a compatible rootstock (RS) that promotes rapid formation of vascular connections between the RS and the scion, and rapid resumption of root and shoot growth. In this study, we used compatible and incompatible Cucurbita rootstocks, with a melon (Cucumis melo L. ‘Arava’) scion, to identify physiological and biochemical factors in the scion-RS interface that could be associated with graft compatibility. Anatomical characterisation of the grafting interface showed that the regeneration and differentiation of vascular elements was similar, at first, in both compatible and incompatible grafted seedlings although, in the latter, a protective layer was formed, but did not interfere with communication between the RS and the scion. Water uptake and sugar distribution between the plant canopy and the roots, measured 14 d after grafting (DAG) were not correlated with compatibility or incompatibility. At 24 DAG, both water uptake and root sugar concentration...

Summary Galia-type melons grafted on to the Cucurbita rootstock ‘TZ 148’ and non-grafted controls were evaluated for vegetative development under greenhouse conditions. In general, the development of grafted and non-grafted plants was similar within a cultivar. The horticultural and pathological performances of the Galia-type melons ‘Carrera’, ‘NUN-5554’, ‘6003’ and ‘Arava’ were evaluated in experiments conducted in non-infested and Monosporascus-infested soils. In non-infested soil, grafted and non-grafted ‘Carrera’, ‘NUN-5554’ and ‘Arava’ had the same yields. The yield of grafted ‘6003’ was signifi cantly higher than that of its non-grafted control. Responses of grafted and non-grafted Galiatype melons to Monosporascus cannonballus were evaluated and compared in the spring and autumn growing seasons. Signifi cant differences in disease incidence were found among cultivars, between grafted and non-grafted plants, and between growing seasons. Disease reduction and the benefi cial effect of grafting on yield were more pronounced in the spring. The results indicate that Galia-type melons can be grafted successfully, but the cultivation of the grafted plants should be adapted to each growing area and season.

SummaryMelon (Cucumis melo L.) ‘Arava’ was grafted onto 22 experimental Cucurbita rootstocks including intra- or interspecific hybrids to examine scion-rootstock compatibility and to correlate plant performance under greenhouse and field conditions. The commercial Cucurbita ‘TZ-148’ rootstock and non-grafted plants were used as controls. Numbers of leaves, stem length and plant fresh weights were recorded three weeks after planting. Vegetative growth of the grafted plants varied markedly, indicating differences in compatibility between the scion and rootstocks. A positive correlation was found between number of leaves, stem length and fresh weight of melon plants. No significant advantage in vegetative growth was found in melons grafted onto intra- or interspecific hybrid rootstocks. Stem diameter and number of vascular bundles of the rootstock did not correlate with scion plant fresh weight. Twelve selected rootstocks out of the 22 tested were grown in the field during the spring and autumn, to determine...

The effect of Cucurbita and melon rootstocks on the horticultural and pathological performance of grafted Fusarium-susceptible melons was studied in four field experiments conducted in Fusarium-infested and Fusarium-free soils. The melon/melon combinations performed better than the melon/Cucurbita combinations regarding yield and disease control. In the 1999 experiment conducted in infested soil, Fusarium wilt symptoms were observed only in the nongrafted susceptible melons whereas all grafted combinations were symptom-free. In the 2000 experiment, nongrafted susceptible melons were totally wilted, whereas disease incidence in the melon/melon combinations and in one of the melon/Cucurbita combinations was low. The response of grafted plants to Fusarium wilt was also affected by the susceptibility of the scion. Among nongrafted melon cv. Ananas Ein Dor and those grafted onto Brava rootstock, 82% and 20%, were diseased, respectively, compared with only 36% and 0%, of the nongrafted and grafted `Ofir' melons, respectively. Negligible quantities of fruit were harvested from the nongrafted plants grown in infested soil, whereas high and moderate yields were obtained from melons grafted onto melon and Cucurbita rootstocks, respectively. The yield of the nongrafted melons in Fusarium-free soils were similar to those of all the grafted plant combinations. Susceptible melon scions grafted onto resistant melon rootstocks were less colonized by F. oxysporum f. sp. melonis than the same melons grafted onto the Cucurbita rootstocks.