Leaf removal reduces scion adventitious root formation and plant growth of grafted tomato

- Leaf removal of tomato scion during grafting reduced adventitious root formation.
- Variable levels of leaf removal resulted in corresponding levels of adventitious root formation in three healing chamber environments.
- Leaf removal during grafting reduced early transplant growth in greenhouse studies.
- 50% leaf removal may be the best method for balancing transplant quality and growth while limiting adventitious root formation.

Although grafting tomato with vigorous rootstocks provides the potential for higher yield, grower adoption of this technology has been relatively slow in the United States. One way to help facilitate this transition is to develop simple propagation techniques that yield high quality grafted transplants for small-batch propagators to graft their own plants. Formation of adventitious roots (AR) from the scion can result in poor quality plants and loss of rootstock function/benefit. In this study, a series of greenhouse experiments was performed to investigate how leaf removal (LR) during the grafting procedure affects AR formation and plant growth post-grafting. We applied three treatments, 0% LR, 50% LR, and 90% LR, to the 'BHN 589' scion and then grafted them onto 'Maxifort' rootstock. The experiment included 4 replicated blocks and was conducted in three different healing chambers. Our results indicate that both 50% and 90% LR significantly decreased AR formation in the low (68% RH) humidity chamber, but only 90% LR reduced AR formation in the chambers with high (95% RH) humidity (P < 0.05). Using a second experimental design, we measured plant growth (height, leaf area, shoot and root biomass, stem diameter, and incidence of flowers) 24 to 52 days post-grafting to understand how leaf removal affects transplant quality (as defined by Vu et al., 2013), growth, and development. Plants with 90% LR had significantly lower leaf area and shoot biomass at day 24, but by day 52, only had reduced stem diameter and height compared to 0% LR. Leaf removal during grafting may be a viable method for propagating high quality, grafted transplants and our report indicates that the desired product (plant for sale vs. plant for use) could dictate the use of 50% vs. 90% LR as the higher leaf removal level reduced transplant quality at the estimated time of sale, but did not affect subsequent plant growth.