Grafting for Root-knot Nematode Control and Yield Improvement in Organic Heirloom Tomato Production

Abstract

Organic heirloom tomatoes (Solanum lycopersicum L.) are difficult to grow in Florida as a result of root-knot nematodes (Meloidogyne spp.) (RKN) and hot, humid growing conditions. Although grafting with resistant rootstocks has been shown effective for RKN management in tomato production, little research has been conducted on grafted heirloom tomatoes under Florida conditions. In this 2-year study, two susceptible heirloom tomato scions, ‘Brandywine’ and ‘Flamme’, were grafted onto two hybrid rootstocks, i.e., interspecific tomato hybrid rootstock ‘Multifort’ (S. lycopersicum × S. habrochaites) and tomato hybrid rootstock ‘Survivor’ (S. lycopersicum). Non-grafted and self-grafted scions were used as controls. Three field trials were conducted including the 2010 and 2011 organic field trials as well as a transitional organic field trial in 2011. There was a lack of RKN pressure in the organic field in 2010. In 2011, the RKN population was higher in the transitional field than the organic field, whereas grafting with hybrid rootstocks significantly reduced root galling (P ≤ 0.0001) in both fields. In the organic field, the hybrid rootstocks performed similarly and significantly reduced root galling compared with the non-grafted and self-grafted scions by ≈80.8%. In the transitional field, compared with non-grafted scions, the root galling reduction by ‘Survivor’ (97.1%) was significantly greater than that by ‘Multifort’ (57.6%). In general, tomato plants grafted onto ‘Multifort’ tended to be more vigorous than all other treatments. There was no clear relationship between root galling and tomato yields. Grafting did not significantly affect the total marketable yield for the scion ‘Flamme’ in both years. Total marketable yield was similar among treatments in 2010 but varied in 2011 for the scion ‘Brandywine’. In 2011, the non-grafted ‘Brandywine’ and ‘Brandywine’ grafted to ‘Survivor’ produced significantly higher (P < 0.05) yields than other treatments in the organic field. However, in the transitional field, ‘Brandywine’ grafted to ‘Multifort’ resulted in significantly higher (P < 0.05) yields than the non- and self-grafted ‘Brandywine’ treatments. Grafting with appropriate rootstocks may play an effective role in RKN management during the transition to organic production when high populations of nematodes are present.