2017 ASHS Annual Conference

Seedless cucumbers are a popular and high-value crop found in many local food markets. Parthenocarpic character enables them to set fruit without pollination, in addition, they can be trellised to maximize the use of vertical spaces. Because of these reasons, seedless cucumber is the third most important high tunnel crop following tomatoes and peppers. One challenge of growing seedless cucumbers in high tunnels is low soil temperatures in early season that suppress plant growth even when the air temperature would be adequate for cucumber production. Soil temperatures lower than 63 °F greatly inhibit absorption of water and mineral nutrients of the crop. In USDA plant hardiness zone 6, we found soil temperatures inside a high tunnel in April frequently below 55 °F, which may prevent crop establishment or delay early cucumber production. In this study, we tested the effects of grafting with cold tolerant rootstocks (‘Titan’, ‘Marvel’ and ‘RST-04-109-W’) on yield and early season production of three high tunnel-grown seedless cucumbers, i.e. pickling cucumber ‘Excelsior’, Beit Alpha cucumber ‘Socrates’ and Japanese cucumber ‘Taurus’. Non-grafted plants were included as controls. Grafting was performed using one-cotyledon method. Grafted and non-grafted seedlings were transplanted in the high tunnel on 30 March, 2016. After transplanting, the lowest air and soil temperatures recorded in the high tunnel were 37 °F and 52 °F, respectively, which resulted in transplant failure of non-grafted plants (44% ‘Taurus’, 50% ‘Socrates’ and 83% ‘Excelsior’). Interestingly, all the grafted plants survived during the cold period. Dead plants were re-planted on 14 April. Cucumbers were harvested from 4 May to 8 Aug. The earliest harvests were recorded on grafted ‘Socrates’ and ‘Excelsior’. Regardless of rootstocks, grafted ‘Excelsior’ had a significantly higher yield (1.95 kg/plant) compared with non-grafted ‘Excelsior’ (0.89 kg/plant) in May. ‘Socrates’ grafted onto ‘RST-04-109-W’ rootstock also had a higher yield (2.36 kg/plant) than non-grafted control (1.35 kg/plant) in the same month. During the whole season, ‘Excelsior’ grafted onto ‘Titan’ had higher yield than non-grafted ‘Excelsior’, as well as ‘Excelsior’ grafted onto ‘Marvel’. The highest yield of ‘Socrates’ was observed on grafted plants with ‘RST-01-109-W’ rootstock. Although there was no significant difference in early yields among grafted and non-grafted ‘Taurus’. Regardless of rootstocks, the yields of grafted ‘Taurus’ were significantly higher than non-grafted plants during the whole season. This study indicated that grafting with cold tolerant rootstocks is a promising approach to enhance early season seedless cucumber production in high tunnels.