Integrated Postharvest Management of Anthracnose in ‘Nam Dok Mai Sithong’ Mangoes with Zinc Oxide Nanoparticles and Ozone

Abstract

Anthracnose, caused by Colletotrichum sp., is one of the major postharvest diseases affecting ‘Nam Dok Mai Sithong’ mangoes. This study explored the efficacy of Zinc oxide nanoparticles (ZnO NPs) and ozone (O₃), both individually and in combination, in controlling anthracnose while preserving fruit quality. Two ZnO NPs types (P10 and P20) were evaluated at 0.5, 1.0, and 2.0 g·L⁻¹ using the poisoned food technique. ZnO NPs inhibited Colletotrichum colony growth in an isolate-dependent manner; P20 (~20 nm) showed greater inhibition at 1.0 g·L⁻¹ (27.8–55.6%), whereas P10 (~10 nm) showed no significant additional inhibition at 2.0 g·L⁻¹ (32.1–53.7%) compared with P20 across three isolates. O₃ treatment at 40 mg·L⁻¹ resulted in complete suppression of spore germination that was observed after 30 and 90 min of exposure, but prolonged exposure damaged the fruit lenticel. O₃ treatment at 40 mg·L⁻¹ caused only minimal inhibition of C. siamense colony growth (≤ 3% compared with the control). However, a 10-min exposure significantly reduced disease incidence to 22.2% and reduced lesion diameter to 4.4 mm in inoculated mangoes. The combination of ZnO NPs (P10, 2.5 g·L⁻¹) and O₃ (40 mg·L⁻¹ for 10 min) exhibited significant colony growth inhibition of C. siamense (72.4%), comparable to ZnO NPs alone (69.4%), but markedly greater than O₃ alone (20.0%). Both P10 alone (1.5–2.5 g·L⁻¹) and the sequential application of P10 followed by O₃ fumigation (40 mg·L⁻¹, 10 min) completely suppressed anthracnose, resulting in 0% disease incidence and no lesion development in all treated fruit. Fruit quality was evaluated using non-inoculated mangoes treated with P10, O₃, and their combination; results showed preserved fruit firmness, increased total soluble solids, and maintained visual quality. Zinc residue analysis was conducted at 1.5 and 2.5 g·L⁻¹ to represent the lower and upper application rates. No detectable residues were found in fruit treated at 1.5 g·L⁻¹ P10, and only a very low level (1.37 mg·kg⁻¹) was detected at 2.5 g·L⁻¹. Even at the highest concentration, ZnO NPs residues remained minimal. These results highlighted the combination of ZnO (2.0 g·L⁻¹) and O₃ (40 mg·L⁻¹ for 10 min) as a promising postharvest strategy for managing anthracnose, while preserving mango quality and ensuring residue levels remain within safe limits.