Grafting Methods and Rootstocks for Organic and Heirloom Tomato Growers In the Midwest, Poster Board #070

Grafting is an effective technique for tomato growers looking to reduce soilborne disease organically and increase fruit yield. Many small-acreage and/or organic growers in the Midwest are looking to produce plants themselves, but have difficulty propagating grafted transplants. Once grafted, the plants are moved into a healing chamber where relative humidity is increased and light is eliminated in order to reduce water stress on the scion tissue and promote healing of the graft union. Although the grafting procedure is relatively simple, managing the healing chamber post-grafting can be challenging and can reduce grafting success rates. The goals of this work are to investigate the utility of grafting for tomato growers in the Midwest and to develop techniques that increase the success as well as reduce the cost of grafting for small-acreage and organic growers.  Multiple replicated field trials were conducted in high tunnel and open-field systems during Summer 2011 on commercial farms and university research locations to investigate any potential yield effects related to different grafting techniques and rootstocks. At a commercial farm in Johnson County, ‘Maxifort’ and ‘Trooper’ rootstocks increased fruit yield by 136% and 130%, respectively, and were statistically significant compared to nongrafted ‘BHN 589’ (P < 0.05). In a high tunnel trial at the Olathe Horticulture Research and Extension Center, ‘Maxifort’ and ‘Trooper’ significantly increased fruit yield by 45% and 46%, respectively, compared to nongrafted ‘BHN 589’ (P < 0.05). Removal of scion tissue (leaves) during the grafting process is performed in order to reduce water stress during the healing process and promote successful graft union. Preliminary data from our trials suggests that these propagation techniques, while beneficial during the healing period, may penalize mature plant yield. At the commercial farm in Johnson County, plants that had undergone shoot removal during grafting with ‘Trooper’ rootstocks had significantly lower yield compared those that were grafted with ‘Trooper’ using the standard tube-grafting technique, although all grafted plants had significantly higher fruit yield than nongrafts (P < 0.05). Interestingly, the removal of shoot tissue during the grafting process had inconsistent effects across rootstock genotypes. Grafting with vigorous rootstock can be beneficial to organic and heirloom growers by increasing fruit yield.  However, further research is needed to determine optimum healing conditions and effects that grafting method has on crop productivity.