Assessment of Pathogenicity of Fungal Pathogens Causing Necrotic Leaf Infection of Basella Alba and Control Using Synthetic Metal Complexes

Basella alba L. which belongs to the family Basellaceae, is a popular tropical green vegetable crop widely cultivated for its edible leaves. Fungal pathogens causing necrotic leaf infection leads to major disease of Basella alba. Therefore, pathogenicity of fungal pathogens causing necrotic leaf infection of Basella alba and control using synthetic metal complex was investigated in this study. Fungal isolates obtained from Basella alba leaves with necrotic leaf spots were identified as Diaporthe phaseolorum based on morphological and molecular characterization. Pathogenicity assessments confirmed high disease incidence, with infection rates rising from 42.86–93.33% by day 10 and increasing further by day 20. Greenhouse experiments revealed significantly lower seedling survival (0–28.6%) in pathogen-infested soil, while sterilized soil supported better growth (57.1–71.4%). Antifungal susceptibility tests indicated that FeL₂SO₄·H₂O (L = dimethylglyoxime, 1:2) and CuSO₄ exhibited the strongest inhibitory effects, with MIC values of 250µg/L. Time-dependent growth analysis demonstrated complete inhibition of fungal spore germination within 16–20 hours by both FeL₂SO₄·H₂O and CuSO₄. In field trials, FeL₂SO₄·H₂O significantly reduced disease occurrence to 5.19% in B. alba, whereas CuSO₄ initially caused phytotoxic effects but later allowed plant recovery. Chlorophyll retention was highest in FeL₂SO₄·H₂O-treated plants, while severe chlorophyll loss occurred in untreated, infected plants. Electrolyte leakage assays showed that CuSO₄ and FeL₂SO₄·H₂O induced major ionic disruptions in fungal cells, leading to the release of Na⁺, Ca²⁺, and K⁺. Microscopic analysis revealed extensive cellular damage in infected plants, whereas treated plants displayed preserved structural integrity. These findings suggest that FeL₂SO₄·H₂O and CuSO₄ could be effective in controlling D. phaseolorum infections in B. alba.