Screening of leaf metabolites in historical mulberry trees (Morus alba L.) from different eco-geographical regions of Slovenia

摘要

Key message The article presents the existing genetic resources of historical mulberry trees in Slovenia and reveals that pruning management and geographical distribution exhibit significant effect on certain biochemical traits. Former sericultural regions in Europe retained a number of centuries-old white mulberry (Morus alba L.) trees, which represent both, a valuable natural heritage and outstanding monuments of the very early attempts to establish a European sericulture, since their leaves were traditionally used to feed the silkworm larvae (Bombyx mori L.). The aim of the presented research was to collect data regarding eco-geographical locations of historical mulberry trees in Slovenia and to screen the content of the main metabolites in leaves to determine genotypes of local origin which are superior in individual compounds defined as feed markers. During field excursions, the highest number of mulberry trees was recorded in the Submediterranean region, followed by the Subpannonean, South-Eastern region and Central Slovenia. Pruning recordings revealed that pollarding is traditionally used in the Submediterranean region. The main phenolic compounds identified in leaves were caffeoylquinic acid derivatives, quercetin malonylhexoside, rutin, kaempferol acetylhexoside and isoquercetin. Pruning significantly affected the levels of total protein and quercetin dirhamnosylhexoside, which were higher in the annually pruned trees. Geographical distribution has a significant effect on total proteins as well as on total phenolics, caffeoylquinic acid derivatives and flavonols. Linear discriminant analysis enabled a comprehensive assessment of leaf metabolites and confirmed that mulberries of different Slovenian regions have distinctive biochemical traits. We were able to recognize caffeoylquinic acid, quercetin malonylhexoside, rutin, kaempferol acetylhexoside and isoquercetin as valuable feed markers with respect to their known beneficial effect on silkworm larvae growth and cocoon quality. By reviewing the existing mulberry genetic resources and their leaf metabolites, we highlighted the natural, cultural and scientific value of the white mulberry.