ED Sciences de la Vie et de la Santé
Effects and Mechanisms of Action of Leafamine®, an Animal-Derived Protein Hydrolysate Biostimulant, in Tomato Under Optimal and Heat Stress Conditions.
by Loé MALGOUYRE (BFP - Biologie du Fruit et Pathologie)
The defense will take place at 9h00 - Amphithéâtre Colette et Josy Bové 71 avenue Edouard Bourlaux, 33140 Villenave d'Ornon
in front of the jury composed of
- Michel HERNOULD - Professeur - Université de Bordeaux - Directeur de these
- Muriel QUINET - Professeure - Université catholique de Louvain - Rapporteur
- Virginie LAUVERGEAT - Maîtresse de conférences - Université de Bordeaux - Examinateur
- Soulaiman SARK - Professeur - Institut Agro Rennes-Angers - Examinateur
- Cédric BERTRAND - Professeur - Université de Perpignan - Rapporteur
Tomato (Solanum lycopersicum) is highly sensitive to heat stress, which impairs root growth, reproductive development, and fruit formation. Biostimulants offer a promising approach to improve crop performance, yet their adoption remains limited by the incomplete understanding of their mechanisms of action. This PhD work aimed to characterize the physiological and molecular effects, and the underlying mechanisms of action of Leafamine®, a protein hydrolysate-based biostimulant developed by BCF Life Sciences, under optimal and heat stress conditions. Leafamine® stimulated primary root growth by 15 to 20% under both conditions through increased cell division and expansion. Transcriptomic analyses revealed the upregulation of cell division and expansion genes (CYCD3;3, EXPA15) and the downregulation of heat-stress markers (HSP70, HSFA7). Hormone and metabolite profiling elevated levels of jasmonic and salicylic acid, putrescine, citrulline, and GABA, consistent with activation of stress tolerance pathways. Pre-treated seedlings exhibited reduced growth inhibition during heat exposure, demonstrating a priming effect. Greenhouse trials confirmed the benefits of Leafamine® at the reproductive stage, with yield increases of 22% under optimal conditions and by 26% under moderate heat stress. Yield improvement results from increased fruit weight and number when applied at early floral stages, associated with enhanced medio-lateral cell division in the pericarp, increased seed set, and improved pollen production. Consistent responses were observed across several tomato genotypes, with variations mainly in the timing of response. These findings highlight Leafamine® as a promising biostimulant for enhancing tomato productivity in the context of climate change.