Effect of Self- and Inter-cultivar Grafting on Growth and Nutrient Content in Sweet Basil (Ocimum basilicum L.)

Jason Hollick
Undergraduate (Environmental & Plant Sciences)
Dr. Chieri Kubota
Horticulture and Crop Science

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. In this study, the effects of grafting two cultivars of sweet basil (Ocimum basilicum) 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 for this study. 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 after 21 days after transplanting (DAT) and all remaining plants were pinched at second node. The second harvest for yield and tissue nutrient analysis were performed at 42 DAT. Leaf number, stem length and root weight were not affected by grafting. After 21 DAT, shoot fresh and dry mass was significantly lower in N/DF when compared to ug-N, suggesting that grafting vigorous N to DF rootstocks can limit yields of N. The fresh shoot:root ratio from 42 DAT was significantly higher for DF/N than ug-DF, 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; however, additional research is needed to determine the specific mechanisms affecting graft union formation, and its effect on growth and nutrient transport in basil.