A method to minimize the time needed for formation of mycorrhizas in sweet corn seedlings for outplanting using AM fungus inoculum produced on-farm

- Demonstrated to quicken colonization of roots by AM fungus inocula.
- The method entails incubation of inoculated potting mix at greenhouse temperatures.
- Effective potency of AM fungus inoculum was increased an average of 80%.

A preliminary greenhouse growth phase prior to outplanting allows for earlier stand establishment and the greater profits that early-harvested crops can receive. Inoculation of these crops with arbuscular mycorrhizal [AM] fungi would help combat the effects of low soil temperatures upon phosphorus uptake and establishment of mycorrhizas in the field. Significant establishment of mycorrhizas on roots of sweet corn (Zea mays L.) in the greenhouse is constrained by the approximate two week residence time. Experiments were conducted to examine the benefits of a one week incubation of inoculated potting media at greenhouse temperatures prior to sowing Z. mays seeds upon subsequent development of mycorrhizas. Resulting levels of colonization of roots were contrasted to those of seedlings grown in media that received a 4 °C incubation to inhibit spore germination prior to sowing seeds. Levels of AM fungus colonization were compared to those of other seedlings grown in media with a range of inoculum densities. Pre-incubation of inoculated potting media in the greenhouse prior to sowing significantly increased both percentage root length colonized and total root length colonized by AM fungi 2-5 fold at the 9-11 day sampling period over that in media incubated in the cold room prior to sowing. Comparison to colonization levels in plants exposed to a range of inoculum densities showed that warm incubation increased the effective inoculum density an average of 80%. Pre-incubation in the greenhouse of AM fungus inoculated compartmented flats of potting media proved to be an effective way to enhance formation of mycorrhizas and should prove to be an effective tool to enhance the effective potency of inoculated potting media.