From disorder to recovery: unraveling hyperhydricity insights in Vaccinium vitis-idaea L. through phytochemical and gene expression studies

Abstract Vaccinium vitis-idaea L. (lingonberry) is a health promoting northern berry crop valued for its antioxidant properties and is commonly propagated through in vitro techniques. However, the success of micropropagation is often hindered by hyperhydricity (HH), a physiological disorder that causes shoots to become water soaked and malformed. This study is the first investigation of HH in the lingonberry cultivar ‘Erntedank’ (Cv1), using a combination of structural, biochemical, and gene expression analyses. Lingonberry shoots grown in both liquid and semi-solid culture media developed typical HH symptoms, including excessive water accumulation and distorted tissues. Treatment with potassium silicate (K₂SiO₃) significantly reduced water content and improved shoot appearance over time. Scanning electron microscopy (SEM) showed distorted stomata, trichomes, and vascular tissues in hyperhydric shoots, which were restored upon silicon treatment. Biochemical profiling, using ultra-high-performance liquid chromatography coupled with mass spectrometry (UHPLC-MS/MS), showed that HH increased the levels of stress related compounds, such as anthocyanins and phenolic acids, which were reduced after silicon treatment. Gene expression analysis using reverse transcription quantitative polymerase chain reaction (RT-qPCR) revealed an over 30-fold upregulation of antioxidant genes (CAT1, APX, and SOD) and ethylene related genes (ACO1, ACS11, COX2, and ETR1) in HH tissues, which were further downregulated following silicon treatment. Therefore, the findings from this study suggested that hyperhydricity in lingonberry is linked to oxidative and hormonal stress, and that silicon supplementation offers a promising strategy to prevent or recover from this disorder, improving the efficiency and quality of lingonberry micropropagation.