Physiological and Biochemical Mechanism of Mycorrhizal Fungi Improving the Resistance of Poplar to Canker Disease

This study investigated the changes of biochemical index and the proteins associated with disease resistance after inoculated with arbuscular mycorrhizal fungi(AMF) of Glomus mosseae and ectomycorrhizal fungi(ECMF) of Boletus luridus on the growth of healthy poplar 107(Populus×euramericana cv.'74/76') and the poplar attacked by canker disease.The possible mechanism of disease resistance induced by mycorrhizal fungi was primarily discussed.The results indicated that both AMF and ECMF significantly decreased the index and incidence of poplar canker disease and increased the content of chlorophyll,bark soluble protein content and root activity.In addition,both AMF and ECMF can decrease the content of malonaldehyde(MDA) and increase the free proline contents.The activity of superoxide dismutase(SOD) and phenylalnine ammonialyase(PAL) in diseased sites.AMF significantly induced the boost of activity of chitinase and β-1,3-glucanase in diseased sites,but ECMF just had a little effect.The index related with resisting canker disease among AMF was superior to ECMF,but both the incidence and disease index of canker disease of AMF were lower than ECMF,the effect of AMF was better when inoculating the poplar seedlings.It is clear that mycorrhizal fungi can improve the absorption of nutrient and growth of poplar when attacked by canker pathogen,the activity of protective enzyme and resistant compound were increased in the mycorrhizal poplar seedlings,producing large amount of chitinase and β-1,3-glucanase to induce secondary defending reaction of poplar.Consequently,mycorrhizal fungi can remedy the harm of disease and improve the disease resistance of poplar.