International Journal of Sustainable Development and Science | 2021
Effects of Salicylic Acid in The Normal and Nano Form Against Selected Fungi That Infect Citrus Trees (Citrus sinensis)
Abstract
Evaluation of the potential antifungal activity of salicylic acid in the normal and nano form on the pathogenic fungi (Alternaria alternata and Penicillium digitatum) causing citrus leave spots and fruit decay was studied under in vitro and in vivo conditions. Characterization of prepared salicylic acid nanoparticles (SA NPs), i.e., size distribution and the stability showed that, size distribution range mainly within 8-40 nm as well as hydrodynamic size for produced nanoparticles is 8-40 nm. Salicylic acid nanoparticles and bulk material at 0.5 and 1 mM, in vitro significantly reduced the mycelial growth for Alternaria alternata and Penicillium digitatum, whereas there was not a significant difference between salicylic acid nanoparticles and bulk material, however significant changes of the linear growth were noticed between the low and the high concentrations. Examinations using transmission electron microscopy (TEM) showed hyphal and conidial deformations in addition to changes in cellular structure of A. alternata and Penicillium digitatum when treated with salicylic acid nanoparticles at 1mM concentration. In case of Alternaria alternata, an increasing of the spinulose conidial cell wall and cell membrane showed and appearance of numerous vacuoles in the cytoplasm with undefined cytoplasmic organelles as well as well-defined ultrastructure organelles of the mycelium, meanwhile in case of Penicillium digitatum salicylic acid nanoparticles exhibited a disrupted cell wall (CW) and several invaginations in the cytoplasmic membrane; shrinkage and decrease in thickness with completely cytoplasmic organelles leakage and accumulation of salicylic acid nanoparticles. The effect of salicylic acid in the normal and nano form were evaluated under field conditions against phytopathogenic fungi Alternaria alternata and Penicillium digitatum on Valencia orange in Ismailia governorate during growing season 2019/2020, salicylic acid in the normal and nano form, significantly reduced the percentages of disease incidence for both Alternaria alternata and Penicillium digitatum compared with the untreated control under field conditions.