Chemotyping and in vitro conservation of strawberry tree Arbutus unedo L., Ericaceae

João Martins is a PhD student at the University of Coimbra and University of Aveiro, Portugal, under the supervision of Prof. Jorge Canhoto and Prof. Glória Pinto. His thesis aims to understand the mechanisms behind abiotic and biotic stress resistance of Arbutus unedo (Ericaceae, strawberry tree), a high resilient Mediterranean tree, with a great ecological importance and valuable applications in the pharmaceutical and food industries. To shed light on this neglected crop, three main lines of research are being followed: i) study of the tolerance mechanism under water limitation, ii) microbiome characterization and chemical fingerprint and their relevance for plant defence, and iii) breeding and propagation of selected superior genotypes. To tackle these themes, physiological, biochemical and metabolomic data were collected from plants under water stress. Bacteria and fungi communities were identified by 16S and ITS rRNA sequencing, and biochemical tests were carried out to assess their ability to solubilize phosphate and to produce ammonia, siderophores and indole-3-acetic acid (IAA). Enzymatic studies using specific substrates were also performed and their antagonistic ability against A. unedo pathogens was tested. The main findings were that strawberry tree has a typical isohydric behaviour under drought, through tight stomatal control. Several key hormones (e.g., abscisic and salicylic acids) were up-regulated on plants under stress and a specific metabolomic profile was determined on high tolerant genotypes. Furthermore, strawberry tree harbours a diverse fungi and bacteria community that produces several enzymes. These enzymes can reduce the effect of the most relevant strawberry tree pathogens, such as Phytophthora cinnamomi, playing a key role in plant defence mechanisms. A similar antagonistic effect was obtained from a crude extract of A. unedo leaves as well as isolated phenolics (arbutin and hydroquinone), which revealed a complex and intricate defence mechanism. Finally, selected genotypes are being micropropagated, for conservation purposes and large-scale production. These findings are expected to have an impact in strawberry tree research and improve farming and forestry practices in the near future.

João Martins won the ISHS Young Minds Award for the best oral presentation at the IX International Scientific and Practical Conference on Biotechnology as an Instrument for Plant Biodiversity Conservation (physiological, biochemical, embryological, genetic and legal aspects), which was held virtually in Thailand in July 2021.

João Martins, Departamento de Ciências da Vida, Colégio de São Bento, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal, e-mail: joao.martins@uc.pt

The article is available in Chronica Horticulturae