Influence of Arbuscular Mycorrhizal Fungi and Sodium Chloride on Fusarium Root Rot and Antioxidative Abilities in Asparagus Plants

Influence of arbuscular mycorrhizal fungi IAMF, Glomus sp. R10 (Gr) and Gigaspora margarita (GM)] and sodium chloride (NaCl) on Fusarium root rot and antioxidative abilities in asparagus (Asparagus officinalis L., 'Welcome') plants was investigated. AMF plants accumulated higher dry weight of shoots than non-AMF plants with or without NaCl treatment during 16 weeks after AMF inoculation. Ten weeks after Fusarium oxysporum f. sp. asparagi (Foa, MAFF305556, N9-31, SUF1226, and SUF844) inoculation, the incidence and severity of Fusarium root rot were eased in AMF plants; most of the Gr plants showed lower severity than GM. In this case, a synergetic effect in disease suppression occurred in some of the AMF plants treated with NaCl. As for antioxidative ability, SOD activity of shoots and roots increased in most of the Gr plants in both NaCl- and non-treated plants 10 weeks after Foa inoculation. Gr plants had higher DPPH radical scavenging activity of shoots and roots than non-mycorrhizal plants with or without NaCl, especially 16 weeks after AMF inoculation. Ascorbic acid contents of shoots and roots increased in most of the Gr plants without NaCl treatment both 16 weeks after AMF and 10 weeks after Foa inoculation. From these findings, AMF induced a growth promotion effect and alleviation of Fusarium root rot in asparagus plants, and the synergetic effect of disease suppression could be expected by the combination use of AMF and NaCl. In addition, it supposed that changes in antioxidative ability might be associated with disease reduction in mycorrhizal asparagus plants.