Use of grafting and calcium cyanamide as alternatives to methyl bromide soil fumigation and their effects on growth, yield, quality and fusarium wilt control in melon

Grafting melon (Cucumis melo L.) seedlings on to the Fusarium oxysporum f. sp. melonis (Fom) commercial resistant squash rootstocks 'Mamouth' and 'Nun 9075 RT' and soil sterilization with calcium cyanamide (CaCN2, Perlka) were tested in 2001 and 2002 as alternatives to methyl bromide (MB) soil fumigation. Ungrafted seedlings of the F-1 melon hybrid 'Galia' were cultivated: (i) in soil sterilized by MB and then artificially infested with Fom (this served as a control), (ii) in soil artificially infested with Fom and then sterilized by MB, (iii) in soil artificially infested with Fom and then sterilized with CaCN2 (Perlka), grafted seedlings on the commercial rootstocks, (iv) 'Mamouth' and (v) 'Nun 9075 RT' were cultivated in soil sterilized with MB and then artificially infested with Fom. The grafted plants on 'Mamouth' and 'Nun 9075 RT' and plants in the Perlka treatment (2001) developed mild symptoms, as indicated by the significantly lower leaf symptom index (LSI; average values 1.06, 1.08 and 1.07) and disease index (DI; average values 1.60, 1.25 and 2.33), respectively, when compared with the controls (average values of LSI = 2.65 and DI = 5.06). Plants grafted on 'Mamouth' and 'Nun 9075 RT' and plants in the Perlka treatment (2001) were more vigorous than the controls as assessed on plant height, stem diameter and root biomass. When compared with the controls, this resulted in an increased (over years) early production (326.3, 265.8 and 489.1%) and late production (371.0, 357.0 and 404.2%). Fruit size was also larger in early production (29.2, 50.9 and 32.3) and late production (4.3, 15.2 and 26.0). The total soluble solids ((o)Brix) increased (over years) in early production (27.4, 39.6 and 47.9) and late production (7.59, 10.07 and 5.6) when compared with the controls. Thus, grafting on resistant squash rootstocks 'Mamouth' and 'Nun 9075 RT' and soil sterilization with Perlka had positive effects on growth, production and fusarium wilt control in melon.