Hybrid Cucurbita Rootstocks Improve Root Architecture, Yield, Quality, and Antioxidant Defense Systems of Cucumber (Cucumis sativus) Under Low Temperature Conditions

Cucumber (Cucumis sativus L.) is one of the sensitive vegetable species to low temperature stress. In recent years, grafting technology has been utilized to meet consumer demand for better price in off-season growing periods. In this study, the performance of two cucumber cultivars grafted onto 12 Cucurbita hybrid rootstocks were investigated at low temperature in Samsun, Turkey. The root morphology and biochemical characteristics of grafted and non-grafted cucumber plants in temperature-controlled and light-controlled greenhouses were determined. In addition, in the late autumn period, under unheated greenhouse conditions, the effects of rootstocks on yield and quality of cucumber plants were investigated. The root system architecture (RSA) (root length, root surface area, and root volume) of the grafted plants under low-temperature conditions was found to be approximately four times higher than the non-grafted plants. Fruit skin thickness, fruit flesh-skin firmness values increased as a result of grafting Fruit color, total soluble solids (TSS), fruit appearance, and taste values were not affected by grafting Under low-temperature conditions, the number of fruits per plant, yield and late yield values were significantly affected and increased with rootstock use. The average yield of the non-grafted cucumber cultivars was 24.8 t/ha while the highest total yield was 55.2 t/ha and 49.2 t/ha in cucumber cultivars grafted onto HMO21 and HMO20 rootstocks, respectively. The average superoxide dismutase (SOD), ascorbate peroxidase (APX) and glutathione reductase (GR) enzyme activities of the grafted combinations were better under low-temperature conditions and increased by 5%, 15%, and 7%, respectively compared with non-grafted plants. Furthermore, malondialdehyde (MDA) concentration in scion x rootstock combinations was 40% lower and the hydrogen peroxide (H2O2) content was also found 30% lower than non-grafted plants. It was determined that HMO9, HMO20 and HMO21 hybrid C. moschata rootstocks showed better performance under low-temperature conditions. It was also determined that in the selection of low-temperature tolerant cucumber rootstocks, APX enzyme activity and root surface area may be an important selection and breeding criteria. (C) 2020 Friends Science Publishers