Impact of Combined Rootstock Cultivar and Grafting Method on Growth, Yield, and Quality of Soilless-Grown Cucumber (Cucumis sativus L.) in a Non-Temperature-Controlled High Tunnel

Growers rarely use the grafting method on a double-root system due to limited information on the added advantages for increased plant vigour and yield of soilless-grown cucumber (Cucumis sativus L.). The study aimed to investigate the effect of combining rootstock cultivar and the grafting method on the growth, yield, and quality of soilless-grown cucumber in a non-temperature-controlled (NTC) tunnel. Two rootstock cultivars, Flexifort (Flex) (Cucurbita maxima × Cucurbita moschata) and Ferro (Fer) (C. maxima × C. moschata), were grafted with scion cultivar Hoplita (H) to either single- (1R) or double- (2R) root systems, and the original scion root system was combined with either a Flexifort or Ferro rootstock (O1R) to two root systems and a non-grafted plant (Hoplita). Plants were grown in 10 L containers filled with sawdust as a growing medium. The leaf number was higher in ‘HO1RFlex’ combinations, while the non-grafted plants had a significantly lower leaf number. Thicker stem diameter was obtained from non-grafted plants. The tallest plants were obtained from HO1Fer combinations at 39, 53, and 101 days after transplanting (DAT), while non-grafted plants at 25 and 101 DAT were the shortest plants. Plants grafted to single- or double-root systems, regardless of rootstock cultivar, had higher early, marketable, and total yield compared to non-grafted cucumber. Many medium-sized fruits were obtained in ‘HO1RFlex’ combinations during the early harvest. The total soluble solids (TSSs) of cucumber juice were higher in ‘H1RFer’ while fruit mineral content was not affected by the combined rootstock cultivar and grafting method. Grafting to a double-root system using the original scion roots combined with rootstock or double rootstock had a limited effect compared to plants grafted to a single-root system. It is recommended that scion be grafted to a single-root system of either rootstock Ferro or Flexifort compared to a double-root system, particularly for the cost effectiveness of seeds and labour used in grafting, as well as for improved vegetative growth, including early marketable and total yield of cucumber. The growing containers of various sizes need further investigation to allow for the root extension and growth of grafted plants.