Improving cucumber tolerance to major nutrients induced salinity by grafting onto Cucurbita ficifolia

To test the possibility that using appropriate rootstock could improve cucumber tolerance to salinity induced by major nutrients, a greenhouse experiment was conducted to determine plant growth, leaf physiological responses and mineral contents of cucumber plants (Cucumis sativus L. cv. Jinchun No.2), either self-grafted or grafted onto the rootstock ‘Black Seeded’ figleaf gourd (Cucurbita ficifolia Bouché) and ‘Chaofeng Kangshengwang’ (Lagenaria siceraria Standl.). Plants were grown in nutrient solutions with 1, 4 and 8 times the concentration of macronutrients in the base solution for 10 days, while the concentrations of micronutrients were the same, making the electrical conductivity (EC) value as 1.9, 5.7 and 9.8 dS m−1, respectively. The results showed that EC treatment significantly decreased scion (the part above graft union) dry weight, leaf relative water content, iron (Fe), manganese (Mn) and phosphorous (P) contents, but increased leaf electrical leakage (EL), malondialdehyde (MDA), nitrogen (N), potassium (K), calcium (Ca) and magnesium (Mg) contents of all grafted plants. However, compared with the self-grafted plants, cucumber plants grafted onto ‘Black Seeded’ figleaf gourd had higher scion dry weight not only under 1.9 dS m−1 treatment but also at 5.7 and 9.8 ones, and these plants could significantly alleviate scion growth reduction, maintain higher soluble sugar and manganese (Mn) contents, higher superoxide dismutase (SOD) and peroxidase (POD) activities, but lower EL and MDA contents at 5.7 dS m−1. In short, grafting cucumber onto ‘Black Seeded’ figleaf gourd could increase plant tolerance to salinity induced by major nutrients.