Grafted Vegetable Transplants for Earliness and Productivity during Northern Field Seasons

Grafting vegetable seedlings for field production is expected to decrease days to crop maturity while increasing yields, improving ability to withstand unfavorable climatic conditions, and enhancing resistance to soil-borne diseases and nematodes. Although studies are under way evaluating grafting in various North American regions, assessments of suitable rootstocks, cultivars, and crop benefits for using grafted vegetables are limited in high latitude areas. Grafting may be a technique to increase earliness and yields of fruited vegetables in regions of short growing seasons and cold soils. A field test was initiated in the interior of Alaska to evaluate grafted tomatoes for productivity and rate of development. The selected tomato cultivar for the study was ‘Beaverlodge Slicer’ because of its adaptation to produce mature tomatoes in the time frame of high latitude field seasons. The selected rootstocks were ‘Maxifort’, ‘DRO138TX’ and 'SuperNatural®'. The ‘Maxifort’ rootstock has been used extensively for year-round greenhouse produced tomatoes. ‘DRO138TX’ is considered less vigorous than ‘Maxifort’ and may be better suited to shorter production cycles in unheated greenhouses or high tunnels. ‘SuperNatural®’ is a recently developed rootstock and recommended for certified organic growers. The scions and the rootstocks were seeded in a greenhouse and the seedlings were grafted three weeks later. As control treatments, non- and self-grafted transplants were included. Four weeks from grafting, the plants were field planted during the first week of June, in 60 cm wide raised beds covered with black polyethylene plastic. Harvest started on 31 July and continued until 30 Aug. Preliminary results suggest limited advantages of grafting tomatoes on rootstocks for earliness and productivity. The highest yields were recorded for intact and self-grafted ‘Beaverlodge Slicer’ at 2.2 ± 0.15 kg per plant. There were no differences in productivity or earliness among plants grafted on the three rootstocks. The average yield per plant for tomatoes grafted on the selected rootstocks was 1.6 ± 0.13 kg. Although these results did not show significant yield improvements, additional studies are necessary to include additional cultivars, crop management procedures, field locations and seasonal conditions to fully evaluate grafting for field production of tomatoes at high latitudes.