Povrćarstvo, ukrasno, aromatično i ljekovito bilje 48. hrvatski i 8. međunarodni simpozij agronoma | Dubrovnik | Hrvatska 393 ORIGINAL SCIENTIFIC PAPER Effect of salinity on grafted and ungrafted watermelon Viktória Bhm, László Gáspár, Gábor Balázs, Dávid Fekete, Noémi Kappel Corvinus University of Budapest, Department of Vegetable and Mushroom Growing, 29-43 Villányi Street, Budapest H-1118, Hungary (viktoria.bohm@uni-corvinus.hu) Summary The aim of our study was to examine watermelon cultivar 'Esmeralda' grafted onto 2 different types of rootstocks (Lagenaria and interspecific squash hybrid) under saline conditions. For control, non-grafted watermelon, and even self-grafted plants were used. Plants were planted in 12 l container filled with peat on 23rd May. Salt applications were started after a month. The treatments consisted of 3 levels (control, 100 mmol, 150 mmol) for 10 days, using sodium chloride (NaCl). At the end of the treatments shoots of plants were sampled. The shoots, leaves and roots fresh weights were measured. The fresh shoot and leaves weight were significantly higher in case of watermelon grafted onto interspecific squash rootstock in every treatment. There weren't any differences in shoot and leaves fresh weight between the self-rooted self-grafted and Lagenaria-grafted plants. No significant difference were observed in fresh root weight between the Lagenaria/watermelon and squash/watermelon combinations, but compared to the non- grafted and self-grafted ones, they showed significantly better growth in every treatments. The roots of Lagenaria-grafted plants were particularly strong at control treatments. Based on the aspects studied interspecific squash hybrid is the most suitable rootstock for watermelon under saline conditions. Key words: watermelon, salt stress, grafting, Lagenaria, interspecific squash hybrid Introduction Grafting vegetables onto compatible rootstocks offers a number of advantages and therefore many experiments have been published on the subject in the recent years. Grafts have been used to induce resistance against low (Bulder et al., 1990) and high (Rivero et al., 2003) temperatures and against iron chlorosis in calcareous soils (Romera et al., 1991) and to enhance nutrient uptake and mineral nutrition (Pulgar et al., 2000; Ruizet al., 1997), increase synthesis of endogenous hormones (Proebsting et al., 1992), reduce uptake of persistent organic pollutants from agricultural soils (Otani and Seike, 2006), raise salt and flooding tolerance (Estan et al., 2005; Yetisir et al., 2006), and limit the negative effect of boron and copper toxicity (Edelstein et al., 2005, 2007; Rouphael et al., 2007). Salinity is one of the major abiotic stresses that could reduce plant growth. It can be a serious problem in arid and semi-arid regions where the area is prone to salinity due to irrigation. Moreover in many irrigated areas of the arid and semi-arid regions, farmers are forced to use saline water to irrigate their crops due to an inadequate supply of fresh water. Using rootstocks capable of ameliorating salt-induced damage to the shoot can be a solution to avoid yield loss in salt sensitive genotypes belonging to Cucurbitaceae family (Uygur and Yetisir, 2009). The use of grafted seedlings in vegetable growing, particularly in watermelon has also increased dramatically in Hungary. The size of grafted watermelon area has grown from 200-300 hectare to 1000-1500 hectare in the last 5 years.