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

ABSTRACT
Basella alba, an important leafy vegetable, is significantly affected by necrotic leaf disease caused by Diaporthe phaseolorum, leading to yield loss. This study assessed the pathogenicity of D. phaseolorum and the efficacy of synthetic metal complexes in disease management. Infected leaf samples were collected from farms in Ado-Ekiti, Nigeria, and the fungal isolates were identified using morphological and molecular methods. The pathogen was confirmed as D. phaseolorum with a 99.44% and 98.37% identity match for two isolates based on BLAST analysis. Pathogenicity trials showed a Disease Severity Index (DSI) of 75% in untreated plants, with high disease incidence at 28–30°C and >80% humidity. To control the disease, synthetic metal complexes of copper, zinc, and iron were synthesized and applied. Antifungal tests revealed that FeL₂SO₄•H₂O (L = dimethylglyoxime, 1:2) and CuSO₄ demonstrated the highest efficacy, with MIC values of 62.5 µg/mL and 125 µg/mL, respectively. Greenhouse trials showed a significant reduction in disease incidence, with FeL₂SO₄•H₂O reducing infection to 3.9% and CuSO₄-treated plants exhibiting complete disease suppression after two weeks. Additionally, metal complex treatments preserved chlorophyll content (FeL₂SO₄•H₂O-treated plants retained 2.12 nm chlorophyll a, compared to 0.227 nm in untreated infected plants). Electrolyte leakage analysis indicated increased Na⁺, Ca²⁺, and K⁺ levels in D. phaseolorum exposed to metal complexes, confirming their antifungal mode of action. Statistical analysis confirmed the significant impact of treatments (p < 0.05). This study highlights the potential of synthetic metal complexes as a sustainable disease management strategy for Basella alba, with implications for broader agricultural applications.