Cassorrhizal Colonization: A Hostless Framework for Mycorrhizal Symbiotic Induction

This version documents the morphological changes observed in the experimental isolate (suspected Lactarius rubidus) across the J160 gellan gum media series since inoculation on 03/28/2026, with comparative reference to the dextrose peptone agar saprobic baseline. All imaging was conducted at 100x magnification under consistent conditions. The DPA baseline documents the saprobic default state: long, exploratory hyphae with sparse dichotomous branching, minimal nodular body expression, and no lateral network connectivity. The J1601 intermediate condition produced a substantial departure from baseline including increased branching frequency, early reticulate network organization, and pronounced internal colony zonation with dense nodular body accumulation near the inoculation point — consistent with a graded developmental response to the TCA cycle and pH buffering chemistry. The J1602 full cassorrhizal formulation produced qualitatively distinct architecture across the entire colonized zone: complete reticulate network organization, dimorphic hyphal differentiation, nodular bodies distributed at hyphal junctions, and — most significantly — the emergence of structures morphologically consistent with sclerotia in a fully hostless synthetic substrate. Sclerotial production in ECM fungi is conventionally associated with host-derived carbon subsidy. Its occurrence here directly challenges the host-dependency assumption. A saprobic negative control on J1602 media showed no equivalent architectural response, establishing ECM specificity of the observed developmental changes. Molecular identification and histological confirmation remain pending. Community peer review welcomed. Full protocol in associated documents. DOI: 10.5281/zenodo.19496745