Chitosan Can Induce Rosa roxburghii Tratt. against Sphaerotheca sp. and Enhance Its Resistance, Photosynthesis, Yield, and Quality

Powdery mildew caused by Sphaerotheca sp. is the most serious disease of Rosa roxburghii cultivation. In this study, the foliar application of chitosan induced Rosa roxburghii Tratt. against Sphaerotheca sp. and its effects on the disease resistance, growth, yield, and quality of R. roxburghii were investigated. The results show that the foliar application of 1.0%~1.5% chitosan could effectively control Sphaerotheca sp. of R. roxburghii with the inducing control efficacy of 69.30%~72.87%. The foliar application of 1.0%~1.5% chitosan significantly (p < 0.01) increased proline, soluble sugar, flavonoids, superoxide dismutase (SOD), and polyphenoloxidase (POD) activities of the R. roxburghii leaf and decreased its malonaldehyde (MDA), as well as reliably enhanced its photosynthetic rate and chlorophyll. Moreover, the foliar application of 1.0%~1.5% chitosan notably improved single fruit weight, yield, vitamin C, soluble solid, soluble sugar, total acidity, soluble protein, flavonoids, and SOD activity of R. roxburghii fruits. This study highlights that chitosan can be used as an ideal, efficient, safe, and economical inductor for controlling powdery mildew of R. Roxburgh and enhancing its resistance, growth, yield, and quality.