Effect of self and inter-cultivar grafting on growth and nutrient content in sweet basil (Ocimum basilicum L.)

Grafting of woody crops has been practiced by humans for thousands of years, but since the early 1900s, interest in grafting herbaceous vegetable crops has been increasing rapidly. This technique is known to improve plant nutrient uptake and use efficiency, tolerance to soil-borne disease and adverse environmental conditions, plant vigor and yield. Thus far, research on grafting has focused primarily on fruiting cucurbit and solanaceous vegetables; however, little is known about the response of leafy vegetables and herbs to grafting and whether these crops may also benefit from grafting. While typical compact architecture of these leafy greens makes grafting challenging, potential benefits include grafting vigor and rootstock disease resistance. In this study, the effects of grafting two cultivars of sweet basil on plant growth and inorganic nutrient content were examined. Cultivars 'Nufar' (N), a vigorous and Fusarium wilt resistant cultivar, and 'Dolce Fresca' (DF), a cultivar developed for compact, uniform growth, were selected. Four grafted treatments (scion/rootstock) were created by self-grafting (N/N and DF/DF) and reciprocal inter-cultivar grafting (DF/N and N/DF). Un-grafted plants (ug-N and ug-DF) served as controls. Following growth in a greenhouse, destructive root fresh and dry mass measurements were taken from half of the plants 21 days after transplanting (DAT) and all remaining plants were pinched at the second node. The second harvest for yield and tissue nutrient analysis was performed at 42 DAT during the first experiment and 35 DAT in the second experiment. After 21 DAT, leaf number, stem length, shoot mass, total mass, and shoot:root fresh mass ratio were significantly lower in N/DF when compared to ug-N, suggesting that grafting vigorous N to DF rootstocks can limit yields of N. possibly due to preferential carbohydrate allocation to DF roots. The fresh shoot:root ratio from 42 DAT was significantly higher for DF/N than ug-D, in the first experiment, despite insignificantly different measures of root and shoot mass, suggesting that N rootstocks may have increased water and nutrient uptake efficiency. This was further supported by significantly higher levels of nitrogen content in DF/N than ug-DF or DF/DF. This study indicates inter-cultivar grafting can have significant effect on plant yield and nutrient content in basil. However, further research is needed to determine the specific mechanisms affecting graft union formation, and its effect on growth and nutrient transport in basil.This project was supported by USDA National Institute of Food and Agriculture Specialty Crop Research Initiative program (Project Number: 2016-51181-25404).No embargoAcademic Major: Sustainable Plant System