Grafting is an important horticultural technique used for many crop species. However, some scion/rootstock combinations are considered as incompatible due to poor graft union formation and subsequently high plant mortality. The early identification of graft incompatibility could allow the selection of non-viable plants before planting and would have a beneficial impact on research and development in the nursery sector. In general, visible phenotypes of grafted plants (size, root number, etc.) are poorly correlated with grafting success, but some studies have suggested that some polyphenols could be used as markers of graft incompatibility several months or years after grafting. However, much of the previous studies into metabolite markers of grafting success have not included all the controls necessary to unequivocally validate the markers proposed. In this study, we quantified 73 primary and secondary metabolites in nine hetero-grafts and six homo-grafted controls 33 days after grafting at the graft interface and in both the scion and rootstock woody tissues. Certain biomarker metabolites typical of a high stress status (such as proline, GABA and pallidol) were particularly accumulated at the graft interface of the incompatible scion/rootstock combination. We then used correlation analysis and generalized linear models to identify potential metabolite markers of grafting success measured one year after grafting. Here we present the first attempt to quantitatively predict graft compatibility and identify marker metabolites (especially asparagine, trans-resveratrol, trans-piceatannol and α-viniferin) 33 days after grafting, which was found to be particularly informative for homo-graft combinations.

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BACKGROUND In recent years, biofungicides have drawn increasing interest in vineyards for a more sustainable integrated and copper‐limited pest management. Among alternatives, botanicals could represent valuable tools, being rich sources of biologically active compounds. Conversely to the well‐known antioxidant and biological properties in relation to health benefits, investigation on bioactivity of hot pungent Capsicum sp. products against fungal phytopathogens in vineyards is still scarce. Therefore, the present study aimed at exploring the biologically active compounds profile of a chili pepper (Capsicum chinense Jacq.) pod extract and its antimicrobial properties against some of the major fungal and Oomycetes pathogens of grapevine, including Botrytis cinerea Pers., Guignardia bidwellii (Ellis) Viala & Ravaz and Plasmopara viticola (Berk. & M.A. Curtis) Berl. & De Toni. RESULTS The ethyl acetate‐extracted oleoresin from the most pungent varieties was rich in capsaicinoids and polyphenols (371.09 and 268.5 μg mg−1 dry weight, respectively). Capsaicin and dihydrocapsaicin, hydroxycinnamic and hydroxybenzoic acids and quercetin derivatives were the most abundant, while carotenoids represented only a minor fraction. The oleoresin was efficient to inhibit all three pathogenic fungi and ED50 values were determined, evidencing that G. bidwellii was the more sensitive (0.233 ± 0.034 mg mL−1). CONCLUSION The results suggested a potentiality of chili pepper extract for the control of some important grapevine pathogens, their possible application being helpful for the recommended limitation in extensive use of copper in vineyard. The complex mixture of high amounts of capsaicinoids, associated to specific phenolic acids and other minor bioactive components might contribute to the observed antimicrobial action of chili pepper extract. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Grapevine canes are vine growing byproducts studied for their antimicrobial activities. These properties are directly connected to the stilbene content; oligomeric stilbenes being the most active. In this study, we propose a chemical process, based on oxidative coupling, using metals to increase the oligostilbene rate and the biological effectivity of cane extract against grapevine pathogens. A total of ten compounds were obtained and identified by combining LCMS and NMR spectroscopies, including four newly reported compounds: trans-oxistilbenin C, trans-oxistilbenin D, and cis- and trans-oxistilbenin E. The extract and the main stilbene formed were evaluated for their preventive effects on Plasmopara viticola and Botrytis cinerea growth. The processed extract was highly effective against both pathogens.

<p>During the process of photosynthesis, leaves capture CO<sub>2</sub> from the atmosphere and rapidly convert it into a diverse array of primary and secondary metabolites. Plants maintain a core set of metabolic pathways that ensure the basic building blocks of life that are available for each plant species to function. However, as plants evolved on land, they began to allocate this carbon (C) to innovative secondary metabolites and organs (cuticles, roots, wood) that protected them from abiotic stress (UV radiation, aridity, freezing) and biotic attack (fungal pathogens and insect/animal herbivory). As plants expanded over the land surface and occupied different niches, the amount of C fixed by plants varied and the types of secondary compounds synthesised by plants began to differ. Little is known about the metabolic profiles of the dominant European tree species and how variable the metabolomes of individual tree species are to changes in site conditions such as nutrient availability or soil moisture status. This study took advantage of recent advances in high-resolution mass spectrometry (HRMS) and bioinformatic tools to compare the leaf metabolomes of 14 commercially important tree species grown across three common gardens. Alongside the metabolic profiles, important chemical and morphological data were also collected from the trees during sampling, including targeted analysis of specific leaf metabolites such as proteins and phenolic compounds to obtain quantitative information on how their concentrations varied between tree species and site. Our analysis showed that the metabolomes of each tree species statistically differ from one another, and this dissimilarity was highly conserved at all three sites, even though tree growth and mortality rates varied between species and site. Our analysis also clearly highlighted distinct metabolome shifts between angiosperm and gymnosperm tree species, with angiosperms displaying greater concentrations of chlorophyll and amino acids alongside lower C/N ratios. These differences were also accompanied by discrepancies in an important set of secondary metabolites detected with the metabolomic technique. Furthermore, we also found that certain secondary compounds were essential in distinguishing between deciduous and evergreen species or families where targeted analysis could not detect significant differences. Our results indicate that temperate tree species may have conserved chemical 'fingerprints' that provide information on fundamental differences in the activity of certain plant metabolic pathways. This thus provides a promising tool to investigate how and why different plant species allocate C differently over the growing season and defend themselves against diverse abiotic and biotic pressures.</p>

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