Resistance Induction Against White Rot of Tuber Mustard Using Chitosans and Acetyl Salicylic Acid

Introduction: White rot, caused by Sclerotinia sclerotiorum, has recently become a serious threat to tuber mustard cultivation in Hangzhou, China. The objective of this study was to evaluate the inhibitory effect of acetyl salicylic acid (ASA) and three different chitosans (A, B and C) against mustard white rot. The degree of N-deacetylation and the molecular weight of chitosans A, B and C were 85%-1129 kDa, 95%-521 kDa and 75%-607 kDa, respectively. Materials and Methods: The inhibitory effect of chitosans with different concentrations against the mycelia growth and sclerotia formation of 3 isolates of the pathogen was determined in vitro. In addition, the efficacy of chitosans and ASA against mustard white rot was assessed during in vivo tests. After protein extraction, effects of chitosans and ASA on resistance related enzymes including chitinase, β-1,3-glucanase, phenylalanine ammonia lyase, polyphenol oxidase (PPO) and peroxidase (POD) were evaluated. Results: The chitosans reduced the mycelia growth and sclerotia formation of the pathogen. The chitosans showed significant antifungal effect against the disease in vivo. The chitosans and ASA markedly reduced the severity of the disease over time. Moreover, the chitosans and ASA markedly enhanced the level of most of the resistant related enzymes after 3 and 6 days. The chitosan B was found to have the best effect against tested pathogen isolates. Conclusions: The chitosan with the lowest molecular weight was found to be more effective against the disease. In addition, chitosans and ASA were able to significantly increase resistance-related enzymes over time indicating that they can be considered as resistant inducers against mustard white rot.