Mycorrhiza and sodium chloride-induced systemic resistance to Fusarium root rot and changes in antioxidative ability in asparagus plants

Abstract

Tolerance to Fusarium root rot caused by Fusarium oxysporum f. sp. asparagi and induced systemic resistance (ISR) in mycorrhizal asparagus plants with a split root system were evaluated. In addition, the changes in antioxidative ability as expression factor of ISR were also investigated. Asparagus (Asparagus officinalis L. 'Welcome') plants were inoculated with the abuscular mycorrhizal fungus (AMF), Glomus intraradices along with 50 mM NaCl in a split root system (R, treated root parts: L, non-treated root parts). Results showed that AMF-treated plants accumulated higher dry weights of fern and roots than the non-treated plants before Foa inoculation. Dry weight of roots increased in most of the treated plants compared to control plants after Foa inoculation; the increase occurred in both L and R. For Fusarium root rot tolerance, the severity of symptoms was relatively alleviated, not only in R but also in L, especially in the AMF and NaCl treated plants, confirming ISR. In addition, four weeks after Foa inoculation, antioxidative ability increased in most of the treated roots (R) and non-treated roots (L) in the following items; superoxide dismutase, 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity, and total contents of polyphenol and ascorbic acid. These results suggest that ISR was involved in the tolerance to Fusarium root rot with AMF and NaCl treatment. Thus, the ISR may be associated with the increase in antioxidative ability in mycorrhizal asparagus plants.