Unveiling Phyllosphere Fungal Communities in <i>Phytophthora infestans</i> -Infected Potatoes Through ITS Amplicon and FTIR Approaches in the Indonesian Highlands

Highland potato areas in East Java, Indonesia-Sumber Brantas and Tosari-face severe late blight caused by <i>Phytophthora infestans</i>. We profiled phyllosphere fungal communities (phylloplane plus leaf endosphere) on symptomatic potato leaves and examined how management contexts may relate to these assemblages. Leaves from "Granola Lembang" (Sumber Brantas) and "Granola Kembang" (Tosari) were analyzed using ITS amplicon sequencing (Nanopore) and Fourier-transform infrared (FTIR) spectroscopy. After normalization to relative abundances, α-diversity (Observed OTUs, Chao1, Shannon, Simpson) was higher in Tosari; communities were dominated by Ascomycota (putative endophytes/saprotrophs), whereas Sumber Brantas showed lower overall diversity with higher Mucoromycota. PCA of FTIR spectra separated samples by site, consistent with cross-site biochemical differences; however, we do not infer that FTIR differences are caused by community composition, nor that management variables are causal drivers. Instead, we treat management as contextual information that co-occurs with site, cultivar, and environmental/soil differences. Causal inference is not warranted given the two-site observational design, symptomatic-leaf sampling, different cultivars, and limited replication. Within these constraints, our integrative profiling provides hypothesis-generating baselines and suggests that management compatible with reduced chemical inputs may be associated with richer phyllosphere assemblages of potential biocontrol relevance in Indonesian highlands.