Radiation Synthesis of Silver Nanoparticles/Chitosan for Controlling Leaf Fall Disease on Rubber Trees Causing by Corynespora cassiicola.

Silver nanoparticles (AgNPs) were successfully prepared by <italic>γ</italic>-rays irradiation of solution containing 1.0–10 mM of silver nitrate and 1% chitosan. The optical characteristics and particles sizes of AuNPs were determined by UV-Vis spectra and TEM images, respectively. The size of AgNPs increased by the increase of silver concentration or the decrease of chitosan molecular weight in irradiated solution. The<italic> in vitro</italic> test showed that AgNPs inhibited the growth of<italic> Corynespora cassiicola</italic> on rubber-leaf extract media with the inhibitory efficiency of 52.1–100% by treatment of AgNPs with particle size from 15 to 5 nm, respectively. In addition, antifungal activity was found to reach ~100% by the addition of 90 ppm AgNPs. The<italic> in vivo</italic> foliar treatment of AgNPs on 9-month-old rubber plants showed that the treatment with 2.5–12.5 ppm AgNPs on tested plants after inoculation by spraying with<italic> C. cassiicola</italic> spores enhanced the rate of non-disease-infected plants from 6.0 to 93.3%, respectively, compared to the untreated control. The inhibition effect of AgNPs on fungal growth of<italic> C. cassiicola </italic>mycelial was also elucidated via SEM images. The AgNPs/chitosan synthesized by <italic>γ</italic>-irradiation is potentially promising to use as a fungicidal product for treating<italic> C. cassiicola</italic>, a serious pathogen fungus on rubber trees. [ABSTRACT FROM AUTHOR]