2018 ASHS Annual Conference

Tomato grafting is being rapidly adopted by high tunnel growers, particularly those that utilize specialty cultivars. Inter-specific hybrid rootstocks can confer resistance to many soilborne pathogens and may provide added vigor. The objectives of this project were to (1) determine successful grafting methods for small-scale propagators, (2) identify rootstocks that improve crop productivity through on-farm and university research trials, and; (3) evaluate the effects of rootstock genotype on rhizosphere microbial communities (rhizobiome). We investigated the formation of adventitious roots during the propagation of grafted plants. Leaf removal significantly decreased adventitious root formation (P<0.05) and 50% leaf removal led to higher quality transplants. High tunnel trials were conducted from 2013-2016 on three commercial farms (two organic) and at the Olathe Horticulture Center. ‘Arnold’, ‘Maxifort’ and ‘Colosus’ rootstocks provided 20% to 73% increases in fruit yield in our trials (P<0.05). Conversely, ‘RST-04-106’ and ‘RT 1028’ rootstocks provided no benefit under little disease pressure and across four locations. We profiled the root rhizobiome by sequencing bacterial 16s ribosomal rRNA and fungal ITS regions from the rhizosphere and within plant roots from the trial sites. The majority of observed microbial taxa were shared; however, a small percentage (less than 3%, P<0.05) were associated with genotype. Interestingly, a more diverse community was observed on ‘Maxifort’ rootstock. The results of this project identify certain rootstocks that lead to higher productivity for organic and conventional high tunnel tomato growers and show that the rhizobiome of grafted plants is somewhat different than nongrafted tomato. This presentation will highlight the activities and impacts of a North Central Region SARE project (LNC13-355) and was also supported by the Ceres Trust and USDA SCRI.