Effects of Pedicularis kansuensis parasitism on physiological characteristics of grass-Epichloë symbiont under different hemiparasite density

Abstract:

[Objective] Root hemiparasites should be taken into account as another biotic stress of grasses as they take directly water and nutrients from their hosts through haustoria. Cool-seasonal grasses have established mutualistic symbioses with Epichloë endophytes:the grass-Epichloë symbionts perform better than endophyte-free plants in biotic or abiotic stresses. However, few studies have considered the benefits of Epichloë endophyte on the physiological characteristics of host grasses under parasitic stress.[Methods] We performed a manipulated pot experiment with endophyte-infected (E+) and endophyte-free (E-) Stipa purpurea. Host grasses were planted with different densities of the hemiparasitic plant Pedicularis kansuensis. The antioxidant enzymes, osmotic materials and root vitality of S. purpurea were determined during different parasitising periods.[Results] The presence of P. kansuensis increased the malondialdehyde (MDA) and proline content and activities of antioxidant enzymes but decreased the root vitality of S. purpurea, and the physiological parameters of S. purpurea parasitised by high hemiparasite density were higher than low hemiparasite density. Meanwhile, activities of antioxidant enzymes, proline content and root vitality of E+ S. purpurea were significantly higher than in E-counterparts; in contrast, the MDA content of E+ plants was lower than E-counterparts.[Conclusion] Our results suggest that Epichloë endophyte can improve S. purpurea tolerance to parasitic stress by increasing activities of antioxidant enzymes, adjusting cell membrane permeability and strengthening the root vitality of host plants. Consequently, endophyte-infected S. purpurea may be a potential candidate as a biological method for effective and sustainable management of the hemiparasite weed-P. kansuensis.