RECYCLING OF WASTE CROP ROOTS BY EXTRACTION OF SUBSTANCES STIMULATING PLANT GROWTH

Strigolactones (SLs), plant hormones primarily synthesised in roots and released into soil, play crucial roles in plant development, interactions with organisms (beneficial and detrimental) and abiotic stress tolerance, especially drought and nutrient deprivation. Consequently, SLs have attracted significant research attention. Beyond their importance in basic research, SLs exhibit potential applications as bioactive compounds in pharmaceuticals, biostimulants, and effective weed management strategies. The European Green Deal and its Next Generation program emphasise reducing over-fertilisation and reliance on pesticides while promoting sustainable waste management practices within a circular economy. In this context, biostimulants represent a promising strategy for the exploitation of SLs, since the chemical synthesis of SLs is challenging due to their lability and producing analogues like GR24 is expensive and time-consuming. The waste by-product of tomato roots and substrates presents an opportunity to extract SLs, thereby minimising disposal costs. Moreover, utilising naturally produced SLs from plants provides a broader spectrum of bioactive compounds with diverse effects, owing to their structural variability. Nonetheless, their very low concentration in roots poses a challenge to the production of SL-enriched extracts. To address these limitations and create new market opportunities for SL applications, investigating SL content modulation in plants through novel genomic techniques (NGTs) and optimised extraction protocols is essential. Recent studies have highlighted the role of carboxylesterases (CXEs) in SL catabolism. AtCXE15 appears to bind and hydrolyse SLs, while AtCXE20 sequesters them without hydrolysis. These genes could thus be genetically manipulated to modulate SLs concentration in roots. This project aims to assess the potential of tomato by-products (roots and growth substrates) to produce SL-enriched biostimulants. Additionally, it seeks to determine whether orthologs of AtCXE15 exist in tomato and elucidate their roles under various conditions, to pave the way to biotechnological manipulation of this gene. The integrated focus on waste reuse and genetic analysis aims to optimise the production of SL-enriched extracts to be used as sustainable biostimulants in agriculture.