Grafting with Hybrid Rootstocks to Increase Tomato Productivity in the Great Plains

Grafting tomatoes is gaining interest among growers throughout the U.S. for several reasons including organic disease management and increased crop productivity.  Growing space constraints for urban and high tunnel growers limit crop rotation as well as expansion of production area.  Grafting with vigorous rootstocks provides the potential for higher yields without additional growing space. Our main objective is to identify tomato rootstocks that improve productivity and decrease losses from disease for high tunnel and open-field growers in the Great Plains region.  Trials using a replicated randomized complete block design were implemented at 7 sites throughout Kansas: 4 on-farm sites and 3 KSU research stations. Four sites under high tunnel cultivation used the tomato variety ‘BHN 589’ as the scion. Of the 3 open-field sites, one used ‘BHN 589’ as the scion and the other two used the heirloom variety ‘Cherokee Purple.’ Across the sites, we assessed 7 different hybrid rootstocks: ‘Maxifort,’ ‘Multifort,’ ‘Trooper Lite,’ ‘DRO 131,’ ‘Arnold,’ ‘RST 04-106,’ and ‘RT 1028.’ All sites used typical farm management practices and yield data was collected during weekly harvests. Fruit was graded based on marketability and then counted and weighed.  At two high tunnel sites, fruit collected during peak harvest were analyzed for acidity, soluble solids, and nutritional quality. At one high tunnel trial, ‘BHN 589’ produced 74%, 70%, 64%, and 52% higher marketable yield when grafted to ‘Maxifort,’ ‘Multifort,’ DRO 131,’ and ‘Arnold’, respectively, compared to the nongrafted ‘BHN 589’ (P<0.05). ‘Maxifort’ grafted with ‘BHN 589’ also significantly increased marketable fruit yield by 42% in the open-field compared to the nongrafts (P<0.05) when verticillium wilt was evident. ‘Cherokee Purple‘ grafted to ‘DRO 131‘ increased marketable yields by 62% compared to nongrafts at one site. At the other ‘Cherokee Purple’ trial, which had low to moderate levels of root-knot nematode pressure, the rootstock ‘Trooper Lite’ increased marketable yields by 56% compared to nongrafts (P<0.05) and RKN ratings were not significantly different. Rootstocks RT-1028 and RST-04-106 did not increase yields when grafted with ‘BHN 589’ or ‘Cherokee Purple’ tomato scions in both high tunnel and open-field production across several locations indicating the importance of rootstock selection when little disease pressure is evident from soil pathogens. Our results suggest that tomato growers in the Great Plains should be strategic when selecting rootstocks in order to increase crop productivity.