The present work intended to evaluate the applicability of photodynamic inactivation (PDI) of Xanthomonas citri subsp. citri with toluidine blue O (TBO), a commercial photosensitizer, as a strategy to control citrus canker. Assays were conducted with cell suspensions and biofilms, constructed either on polypropylene microtubes (in vitro assays) or on the surface of orange leaves (ex vivo assays), in the presence of TBO and under irradiation with artificial white light or natural sunlight. PDI assays using TBO alone caused a maximum 5·8 log10 reduction of X. citri viable cells in suspensions, and a much smaller inactivation (1·5 log10) in biofilms. However, concomitant use of KI potentiated the TBO photosensitization. Biofilms were inactivated down to the detection limit (>6 log10 reduction) with 5·0 µmol l−1 TBO + 10 mmol l−1 KI (in vitro) or 5·0 µmol l−1 TBO + 100 mmol l−1 KI (ex vivo) after artificial white light irradiation. Under natural sunlight, a reduction down to the detection limit of the Miles–Misra method was achieved with 50 µmol l−1 TBO and 100 mmol l−1 KI. PDI has potential to be applied in the control of citrus canker in field conditions although further studies are needed to show that there are no risks to plant physiology or fruit quality.

中文翻译：

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植物病原细菌 Xanthomonas citri subsp. 的光动力灭活。柑橘

目前的工作旨在评估柑橘黄单胞菌光动力灭活 (PDI) 的适用性。柑橘与甲苯胺蓝 O (TBO)，一种商业光敏剂，作为控制柑橘溃疡病的策略。在 TBO 存在下并在人工白光或自然阳光照射下，用在聚丙烯微管（体外试验）或橙叶表面（体外试验）上构建的细胞悬浮液和生物膜进行试验。单独使用 TBO 的 PDI 测定导致悬液中柑橘叶点霉活细胞的最大减少 5·8 log10，生物膜中的灭活程度小得多 (1·5 log10)。然而，同时使用 KI 会增强 TBO 光敏作用。生物膜被灭活至检测限 (> 6 log10 减少）与 5·0 µmol l-1 TBO + 10 mmol l-1 KI（体外）或 5·0 µmol l-1 TBO + 100 mmol l-1 KI（离体）在人工白光照射后。在自然阳光下，使用 50 µmol l-1 TBO 和 100 mmol l-1 KI 可降低到 Miles-Misra 方法的检测极限。PDI 有可能用于在田间条件下控制柑橘溃疡病，尽管需要进一步研究以表明对植物生理学或果实质量没有风险。