Local Climate and Cultivation Practice Affect Biochemical Composition of Mulberry (Morus sp.) Leaves in Submediterranean and Subpannonian Regions of Slovenia

Mulberry (Morus sp.) trees are known for their adaptability and broad utility in agriculture (silkworm rearing), nutrition, and pharmacology, while also supporting ecosystems through water regulation, carbon storage, and phytoremediation. Their growth and leaf biochemistry are strongly shaped by climate. This study aimed to (1) identify differences of old local white (M. alba L.) and black mulberry (M. nigra L.) leaves, (2) perform a chemotype analysis of monitored local varieties, and (3) evaluate the influence of selected bioclimatic factors and pruning practices on the biochemical composition of leaves of white mulberry trees across Slovenian mesoregions. Black mulberry exhibited a higher phenolic content, particularly caffeoylquinic acid derivatives (16.05 mg/g dry weight (DW)), while white mulberry contained more quercetin glycosides (6.04 mg/g DW). Ward’s clustering identified three chemotypes, two of which had elevated protein and hydroxycinnamic acid levels, making them particularly suitable for silkworm feeding. Considering pruning practices of white mulberries, we determined significantly increased protein contents in yearly pruned trees (187.24 mg/g DW). Principal component analysis revealed interactions between bioclimatic, morphological, and biochemical factors, distinctly separating mulberries from the Submediterranean and Subpannonian macroregions. White mulberries from Subpannonian regions accumulated more caffeoylquinic acids in leaves under lower precipitation and total insolation, while those from Submediterranean regions exhibited higher kaempferol derivatives, due to photo-thermal stress. These findings highlight the influence of climate and pruning on mulberry biochemical diversity and adaptation.

桑树属（Morus sp.）植物以其极强的适应性和在农业（蚕桑养殖）、营养与药理学领域的广泛用途著称，同时还能通过水文调节、固碳以及植物修复（phytoremediation）来支撑生态系统。气候对其生长与叶片生物化学特征具有显著调控作用。本研究旨在达成三项目标：（1）厘清本地古老的白桑（M. alba L.）与黑桑（M. nigra L.）的叶片差异；（2）对监测到的本地桑品种开展化学型（chemotype）分析；（3）评估斯洛文尼亚中观区域内，选定的生物气候因子与修剪措施对白桑叶片生物化学组成的影响。研究结果显示，黑桑的酚类物质含量更高，尤以咖啡酰奎宁酸衍生物为甚，其含量达16.05 mg/g干重（DW）；而白桑则含有更多槲皮素苷类物质，含量为6.04 mg/g干重。沃德聚类（Ward’s clustering）分析识别出三种化学型，其中两类的蛋白质与羟基肉桂酸水平显著升高，因此特别适合用于蚕桑饲养。针对白桑的修剪措施研究表明，年度修剪的桑树叶片蛋白质含量显著提升，达187.24 mg/g干重。主成分分析（Principal component analysis）揭示了生物气候、形态与生物化学因子之间的交互作用，可将地中海次区域与潘诺尼亚次区域的桑树清晰区分开来。在降水与总日照量较低的潘诺尼亚次区域，白桑叶片中的咖啡酰奎宁酸类物质积累更多；而地中海次区域的白桑则因光热胁迫，积累了更高水平的山奈酚衍生物。上述研究结果凸显了气候与修剪措施对桑树生物化学多样性及其适应性的调控作用。