Pre-grafting Foliar Trimming Intensity Effects on Healing and Regrowth of Newly Grafted Pepper Seedlings

Wound healing is a complex process involving a cascade of coordinated reactions at the wound site and elsewhere. Callus formation is a common early step in restoring tissue structure and function. Newly grafted pepper seedlings tend to callus less and require more time to heal than tomato and other routinely-grafted crops, challenging propagators. Since low-intensity wounding can trigger whole-plant responses that may speed wound healing at grafting, we set out to determine if the timing and intensity of scion foliar trimming would influence the success or regrowth rate in newly grafted pepper plants. ‘Aristotle’ and ‘Scarface’ seedlings were grown from seed in a climate-controlled greenhouse at OARDC for thirty-three days. On Day 33 after seeding, non-destructive measures were taken on representative plants and a subset of plants was sacrificed to record plant biomass and other variables. Either 50% or 100% of the leaf area was removed from two other sets of identical plants on the same day with before and after measures confirming that treatment targets were met. The process was repeated on Day 35 after seeding, with untrimmed and trimmed (50% and 100% two and zero days before grafting) scions then splice-grafted to untrimmed rootstock seedlings. Grafted and ungrafted plant condition was monitored for fifteen days after grafting using a total of fourteen destructive and non-destructive measures. Graft success was unaffected by trimming, with success rates exceeding 90% in all treatments. However, levels of grafted plant growth (fresh and dry wt., leaf area) through fifteen days after grafting tended to be greatest when scion seedlings were not trimmed before grafting, although 50% trimming increased rootstock and scion stem diameter near the graft union. Timing showed significant differences in seven variables, whereas intensity presented significant differences in twelve variables. While trimming appears to slow grafted pepper plant regrowth, it did not lower grafting success. If trimming is thought to confer advantages in large-scale grafting operations, follow-up research should focus on why it slowed regrowth in this study.