Effect of the different timing of AMF inoculation on plant growth and flower quality of chrysanthemum

Plant growth and flower quality of an ornamental plant ( Chrysanthemum morifolium Ramat) var. Baekgwang in response to the different timing of arbuscular mycorrhizal fungi (AMF) inoculation were examined. To evaluate the effects of AMF inoculation timing on growth of chrysanthemum cuttings, AMF was directly inoculated to cutting (AMFD), or inoculated at transplanting stage (AMFA). Control plants did not receive AMF inoculation (CON). A significant difference in plant growth was observed in AMF treatment compared to non-inoculated treatment at transplanting stage. Rooting rate in AMF treatment was 99% whereas it was 76% in non-mycorrhizal inoculation. The colonization rate was 3.9% in AMF treatment, while it was 0% in non-AMF treatment. Tap root length and number of lateral roots in AMF treatment were twice than those of non-AMF treatment. Inoculation of AMF significantly increased shoot and root growth at transplanting stage. At 7 weeks after transplanting, chrysanthemum plants in AMFD and AMFA treatments had 46.42 and 34.24% colonization rate, respectively. Low colonization rate (6.08%) was observed in CON, possibly due to contamination. Plant height, leaf area, root length, and fresh and dry weight of shoots, stems and roots in AMF inoculation treatments (AMFD and AMFA) were significantly higher than control plants. AMF inoculation significantly shortened flowering time compared to non-AMF plants. Chrysanthemum in AMFD, AMFA and CON treatments flowered at 98, 104 and 112 days after transplanting, respectively. Fresh weight, width and height of flowers in AMFD and AMFA treatments were generally higher than those in CON. However, a significant increase in fresh weight, width and height of flowers was found in AMFD treatment. A significant increase of macronutrient uptake in leaves was observed for AMFD treatment, compared with CON. Mn uptake in AMFD and AMFA was more than double than that in CON. In roots, macro and micronutrient concentrations were generally higher in AMFD.