Fabrication of pH-Sensitive Tetramycin Releasing Gel and Its Antibacterial Bioactivity against Ralstonia solanacearum

Ralstonia solanacearum (R. solanacearum)-induced bacterial wilt of the nightshade family causes a great loss in agricultural production annually. Although there has been some efficient pesticides against R. solanacearum, inaccurate pesticide releasing according to the onset time of bacterial wilt during the use of pesticides still hinders the disease management efficiency. Herein, on the basis of the soil pH change during R. solanacearum growth, and pH sensitivity of the Schiff base structure, a pH-sensitive oxidized alginate-based double-crosslinked gel was fabricated as a pesticide carrier. The gel was prepared by crosslinking oxidized sodium alginate (OSA) via adipic dihydrazide (ADH) and Ca(2+). After loading tetramycin into the gel, it showed a pH-dependent pesticide releasing behavior and anti-bacterial activity against R. solanacearum. Further study also showed that the inhibition rate of the tetramycin-loaded gel was higher than that of industrial pesticide difenoconazole. This work aimed to reduce the difficulty of pesticide administration in the high incidence period of bacterial wilt and we believe it has a great application potential in nightshade production.