In Planta Evaluation of Plant Extract-Loaded Chitosan Nanocarriers Against Fusarium Wilt: Efficacy Assessment in Controlled Environment Conditions

Fusarium wilt caused by Fusarium oxysporum f. sp. cubense represents one of the most destructive banana diseases worldwide. With tropical race 4 (TR4) threatening global production and limited resistant varieties available, innovative biocontrol strategies are essential. Following promising in vitro results, this study evaluated the protective efficacy of chitosan-based nanocarriers loaded with Rubia tinctorum and Uncaria tomentosa extracts under controlled greenhouse conditions.

Banana plantlets were treated with nanocarrier formulations and subsequently inoculated with Foc. Disease severity was assessed using a 0-4 scale over 79 days, and the area under disease progress curve (AUDPC) was calculated. Additionally, physiological parameters including stomatal conductance, transpiration rate, and chlorophyll fluorescence were monitored using porometry and fluorometry.

Results demonstrated significant disease reduction with R. tinctorum-loaded nanocarriers, achieving 34.9% control efficacy compared to untreated infected plants (AUDPC: 134.5 vs 206.6). This treatment showed statistically significant differences in disease severity from 31 days post-inoculation onwards, with final severity scores of 2.6 compared to 3.6 in infected controls. In contrast, U. tomentosa formulations provided limited protection (7.8% efficacy, AUDPC: 190.5) with no significant differences from the infected control. Physiological analyses revealed enhanced stomatal conductance and transpiration rates in R. tinctorum-treated plants. Growth parameters demonstrated significant improvements in R. tinctorum-treated plants, including 10-15% increases in leaf width, enhanced leaf length and fresh weight (16% increase), alongside 36-43% higher chlorophyll content compared to controls. DUALEX measurements confirmed elevated flavonoid levels (621.2 vs 318.1) and anthocyanin content (231.0 vs 168.4) in R. tinctorum-treated plants, indicating enhanced stress tolerance.

These findings validate the transition from laboratory to greenhouse conditions, demonstrating that R. tinctorum-based nanocarriers offer substantial disease suppression potential. The integration of nanotechnology with natural bioactive compounds presents a promising sustainable approach for Fusarium wilt management, contributing to the development of environmentally friendly alternatives for banana crop protection in commercial production systems.