Abstract: Exploring the effects of soil pH on the branches, leaves, and juice sac granulation in fruits of Citrus grandis (L.) Osbeck. cv. Guanximiyou provides theoretical support for its scientific cultivation and sustainable development. We carried out an experiment in four Guanximiyou orchards that showcased a uniformity in geographical conditions and tree growth but differed in soil pH (soil pH values were 5.15, 4.76, 4.73 and 4.49, respectively). Illumina HiSeq 4000 highthroughput transcriptome sequencing analysis was performed on the leaves and branches of Guanximiyou, with the aim of isolating differential genes for KEGG enrichment metabolic pathway analysis and identifying associated indicators. The findings showed that a lower soil pH (4.76, 4.73 and 4.49) exacerbated the granularity of Guanximiyou and affected the MAPK signal transduction and plant hormone signal transduction pathways in leaves and branches. Furthermore, soil pH significantly influenced secondary and lactic acid metabolic pathways in branches. Concurrently, a PCR fluorescent quantitative analysis of pertinent genes in signal transduction pathways, such as MAP Kinase Kinase Kinase 18, Protein Phosphatase 2C, Abscisic Acid Insensitive Protein 5, CML46 Calcium Binding Protein, Auxin Response Protein IAA1, and EndoChitinase, was conducted to validate the reliability of the transcriptome data. Soil pH was found to influence the quantities of abscisic acid in leaves and fruits, and the amount of auxin in branches. We conclude that lower soil pH exacerbates the granularity of Guanximiyou, influences the quantities of hormones in fruits, leaves and branches and the expression of genes involved in plant hormone signaling transduction pathways.

Key words: Citrus grandis (L.) Osbeck. cv. Guanximiyou, soil pH, transcriptome sequencing, signal transduction pathway, plant hormone