ASHS 2015 Annual Conference

Roots are the critical sites of water and nutrient uptake in agronomic crops. Certain root characteristics, such as branching, rate of horizontal growth, and root tip density affect a plants ability to utilize soil resources. Nowhere is the importance of root systems seen than in the use of specific rootstocks for grafted plants. Grafting of tomatoes to manage biotic and abiotic stress is a potential strategy to maintain or increase production during environmental stress. Very little research has been conducted to quantify root growth and architecture in tomato rootstocks. Furthermore, no research has focused on the non-destructive analysis of roots of grafted plants. However, with the recent development of the mini-Horhizotron chamber, root systems can be viewed and non-destructively analyzed over time in diverse soil substrates. Utilizing these mini-Horhizotrons, a greenhouse study was conducted twice in 2014 to compare root systems of a commercial determinant tomato (Solanum lycopersicum cv. ‘Tribute’) and two commercially available tomato rootstocks (‘Maxifort’ and ‘RST-106’). These three varieties were self-grafted and also left non-grafted. Additionally, two grafting combinations were made with ‘Tribute’ as the scion on either ‘Maxifort’ or ‘RST-106’. Data collected throughout the trials included total number of root tips, horizontal root tip density, rate of horizontal root growth, and total root length. In general, ‘Maxifort’, regardless of grafting, had a faster rate of horizontal root growth, increase in horizontal root tip density, faster rate of root tip development, and significantly longer root length compared to ‘Tribute’ root systems. This study demonstrates that differences in root system growth and development rate do exist in tomato rootstock varieties. These differences may explain some of the increased vigor observed when utilizing specific rootstocks, however further research is warranted to correlate root system characteristics to yield performance in tomatoes.