S03 - Session P1 - The effect of grafting on organic tomato seed production in Britany

Authors: Hervé Floury, Amelie Detterbeck *, Thibault Nordey

Aiming to reach 25% organically managed land, the EC has set ambitious goals to transform the European Food System. Increase in organic seeds is therefore required to tackle this challenge. The potential of grafting to increase organic seed production was assessed in the present study onto three tomato varieties. Tomato cultivars were grown under organic greenhouse conditions in Britany (2.4 plants/sqm). Cultivars ('Benisoda', 'Berner Rose' and 'Rosa de Barbastro') were either non-grafted (NG), grafted on 'Emperador' (Rijk Zwaan) or 'BRESOV', obtained within the BRESOV project (interspecific hybrid S . glycopersicum x S. habrochaites provided by UPV, Spain). Fruit number and weight were evaluated between 9 th July - 1 st October 2021. Seed counting and Thousand Seed Weight (TSW) were assessed on the first two bunches. Overall seed production was extrapolated based on fruit production. The effects of genotype, grafting and interaction were analyzed (ANOVA/Tukey's HSD, P ≤ 0.05). The experimental results showed yields varied between 8.1-20.0 kg/sqm and seed production between 30.6-98.0 g/sqm. Grafting increased yield and seed production, regardless of variety and rootstock tested. No differences were established between rootstocks. Grafting increased seed production by about 60%. Increase in seed production by grafting was related to the increase in yield, i.e., number of fruit and fruit weight, rather than the number of seeds per kg of fruit which was reduced by grafting, i.e., 1133.8+-382.5 ('Emperador') compared to 1312.4+-285.4 (NG). TSW was not affected by grafting but by interaction effects between different genotypes and rootstocks. Our results indicate that grafting of tomato plants can positively affect seed production in organic conditions. Grafting increased fruit number and fruit weight per sqm resulting in an increased seed production of ~60%. However, interaction effects between genotypes and rootstocks need to be taken into account to exploit the potential of grafting.