A Meta-analysis of Tomato Rootstocks to Determine Rootstock Vigor and Genetic Yield Potential

The practice of grafting tomatoes (Solanum lycopersicum) in the United States is growing in order to utilize rootstocks that confer resistance to soilborne plant pathogens, tolerance to abiotic stressors, and potentially increased vigor. The utilization of grafted plants can be especially beneficial for growers utilizing high tunnels, as limited crop rotation and intensive management practices can facilitate the proliferation of soilborne diseases. Grafting plants with vigorous or disease-resistant rootstocks allows for growers (especially those with limited space, or who are growing in high tunnels) to increase their productivity dramatically without increasing their production space. However, it is currently not clear how to identify which rootstocks show increased vigor and under what conditions. Therefore, the objectives of this study were to: 1) develop a meta-analysis approach to determine the characteristics of vigorous rootstock; 2) identify rootstocks that consistently showed increased vigor both across diverse production systems and under specific growing conditions; and 3) determine the relationship between increased vigor and genetic yield potential using data from on farm research trials. We used a meta-analysis approach to compile research data from 34 replicated grafting trials that were conducted in multiple locations throughout Kansas from 2011-2015. We normalized yield data based on the impact of the rootstock as compared to the nongrafted control within each replication (rootstock/nongraft). We then used the normalized data set to measure the relationships between rootstock varieties and determine which rootstocks conferred the greatest production advantage, and under which growing conditions. Certain rootstocks showed improved production in almost all growing conditions and/or trials. Other rootstocks appear to confer a comparative advantage primarily in growing systems with specific environmental or biological stressors, such as a soilborne disease. By combining data from multiple years and growing environments, this work will enable growers to select rootstocks that are tailored for their specific production system.