Ectomycorrhiza Enhanced the Cold-Acclimation Growth and Freeze Tolerance of Scots Pine (Pinus sylvestris L.)
Authors：Burenjargal Otgonsuren, Ming-Jen Lee
Key words：Phialocephala fortinii, Pinus sylvestris, ectomycorrhiza, freeze tolerance, proline.
Scots pine (Pinus sylvestris) is an economically important source of timber in Mongolia and has been widely used in reforestation programs. Our earlier study showed that Phialocephala fortinii was capable of forming symbiotic ectomycorrhizal associations with Scots pine seedlings. In this study, Phi. fortinii inoculation significantly increased the growth, biomass, and mineral (P, K, Ca, Mg, Na, and N) contents in roots, stems, and needles of Scots pine seedlings under normal and cold-acclimation conditions. Furthermore, the proline content of inoculated Scots pine seedlings was significantly higher than that of non-inoculated ones after hardening and cold-acclimation treatments.
The inoculated and non-inoculated Scots pine seedlings were cold-acclimated and subsequently subjected to freezing tolerance tests at -12, -14, -16, -18, and -20℃ for 7 d, and then cultivated at 12±2℃ for 14 d. Values of the temperature for 50% mortality (LT50) of needles of noninoculated and inoculated Scots pine seedlings were -12 and -15℃, respectively. Consistently, respective LT50 values of seedlings of non-inoculated and inoculated pines were -14 and -18℃. In addition to Phi. fortinii effectively forming ectomycorrhiza with Scots pine seedlings, this study demonstrated that Phi. fortinii significantly improved the growth, nutrition acquisition, proline content, and freeze tolerance of Scots pine.