Nanoparticles and photodynamic therapy in the treatment and control of Alternaria alternata in wheat seeds

ABSTRACT The expansion of wheat crops (Triticum spp.) to the Brazilian Cerrado highlights the need to use pathogen-free seeds. This study aimed at evaluating the efficacy of nanoparticles (NPs) and photodynamic therapy (PhT) in inhibiting the in vitro growth of the fungus Alternaria alternata, in its treatment and control in naturally contaminated wheat seeds, and in the physiological quality of the seeds. The efficacy of NPs (ZnOCl, ZnOCl:1Cu, ZnOCl:0.1Ag; ZnO:1Cu, ZnO, and ZnO:1Ag) and PhT using methylene blue (MB) and toluidine blue (TB) dyes was evaluated in inhibiting the mycelial growth of A. alternata and in the treatment and control of the pathogen in wheat seeds by evaluating germination, emergence, GSI, ESI, accelerated ageing, and health. All NPs at 2.5 and 5 mg mL-1 concentrations and the dyes MB, TB, MB + TB at 50 and 100 µmol L-1 inhibited mycelial growth and reduced the incidence of A. alternata in the seeds. The NP ZnO:1Ag at 5 mg mL-1 and the MB + TB dye at 100 µmol L-1 were the most effective in inhibiting mycelial growth. NPs and PhT did not affect the physiological quality of seeds and controlled A. alternata in wheat seeds, demonstrating potential use in the treatment and control of the pathogen in wheat seeds.

摘要：小麦属（Triticum spp.）作物向巴西塞拉多（Cerrado）的扩张凸显了使用无病原种子的必要性。本研究旨在评估纳米颗粒（nanoparticles, NPs）与光动力疗法（photodynamic therapy, PhT）对链格孢菌（Alternaria alternata）体外生长的抑制效果，及其对自然污染小麦种子的病害防治效果与种子生理品质的影响。本研究测试了ZnOCl、ZnOCl:1Cu、ZnOCl:0.1Ag、ZnO:1Cu、ZnO及ZnO:1Ag等多种纳米颗粒，以及以亚甲基蓝（methylene blue, MB）、甲苯胺蓝（toluidine blue, TB）为光敏剂的光动力疗法对链格孢菌菌丝生长的抑制作用；同时通过测定种子发芽率、出苗率、GSI、ESI、加速老化试验及健康检测，评估二者对小麦种子中该病原菌的防治效果。所有浓度为2.5 mg·mL⁻¹与5 mg·mL⁻¹的纳米颗粒，以及浓度为50 μmol·L⁻¹与100 μmol·L⁻¹的MB、TB及MB+TB复合染料，均可抑制链格孢菌菌丝生长，并降低种子中该病原菌的带菌率。其中，浓度为5 mg·mL⁻¹的ZnO:1Ag纳米颗粒与100 μmol·L⁻¹的MB+TB复合染料，对菌丝生长的抑制效果最为显著。纳米颗粒与光动力疗法均未对种子生理品质造成负面影响，且可有效防控小麦种子中的链格孢菌，展现出用于小麦种子病害防治的应用潜力。