Soil pasteurization and inoculation with Glomus intraradices alters flower production and bulb composition of Zephyranthes spp.

Summary

We assessed whether adding inoculum of the vesicular-arbuscular mycorrhizal fungus (VAMF) Glomus intraradices into growing medium of three Zephyranthes spp (White Rain Lily WRL], Z. candida; Pink Fairy Lily PFL], Z. robusta; Yellow Zephyr Lily YZL], Z. sulphurea) alters aspects of flower and bulb production. Shoots of inoculated plants emerged 7–13 d earlier than those of non-inoculated plants. Inoculation slightly delayed the emergence of flower buds on WRL and PFL, but did not delay the time of flower opening of WRL. Inoculated YZL flowered 4–11.d earlier than non-inoculated plants. The number of flowers produced by YZL was consistently increased by inoculation, while the inoculation with VAMF increased flower production by WRL and PFL only when plants were growing in pasteurized soil. Leaf biomass of inoculated WRL was larger than non-inoculated plants, while leaf biomass was generally smaller in inoculated PFL and YZL. Partitioning of biomass to bulbs and offsets varied with species, soil pasteurization, and inoculation. Inoculation increased the combined weight of bulbs and offsets at the end of the second growing cycle by 50–150%. Inoculated YZL and WRL consistently produced more offsets in the second growing season after inoculation. For all species, inoculation increased phosphorus and carbohydrates and decreased nitrogen and amino acids in bulbs. Adding VAMF into the growing medium of Zephyranthes altered aspects of plant development and biomass partitioning important to flower and bulb production during the first growing cycle after inoculation, and most effects of VAMF inoculation are more pronounced in the second growing cycle after inoculation. Of the three species examined, Z. sulphurea showed the most consistent responses to inoculation.