design: DNA was isolated using the Promega DNA Purification Kit according to the manufacturer's instructions. PCRs were conducted to amplify the bacterial 16S rRNA region using the 515F/806R primer set, and the fungal internal transcribed spacer (ITS) region using the ITS3/KYO2 primer set, along with peptide nucleic acid (PNA) clamps to block PCR amplification of apple plastid and mitochondrial sequences (Caporaso et al., 2011; Toju et al., 2012). PCR conditions were followed as described in our previous studies (Abdelfattah et al., 2021). Library preparation following amplification was carried out as per the Illumina 16S Metagenomic Sequencing Library Preparation guide. Library size, quality, and the confirmation of the absence of adapter dimers were assessed using an Agilent 2100 Bioanalyzer (Agilent). Paired-end sequencing of the amplicons was performed on an Illumina NovaSeq (Illumina) sequencer with a V3 600-cycle Reagent Kit (Illumina).