Author
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Douds, David |
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WILSON, DAVID - King'S Agriseeds Inc |
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ZIEGLER-ULSH, CHRISTINE - Natural Resources Conservation Service (NRCS, USDA) |
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Submitted to: Scientia Horticulturae
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 2/9/2016 Publication Date: 4/15/2016 Citation: Douds, D.D., Wilson, D.O., Ziegler-Ulsh, C. 2016. A method to minimize the time needed for formation of mycorrhizas in sweet corn seedlings for outplanting using AM fungus inoculum produced on-farm. Scientia Horticulturae. 203:62-68. Interpretive Summary: Farmers can reap financial rewards by being first to market with their vegetable crops. One way of doing this is to grow sweet corn in the greenhouse for two weeks and then out plant to the field early in spring. This avoids the negative impact of cold soil temperatures upon germination of the seeds. One problem with this procedure is the reduced capacity of plant roots to grow and absorb mineral nutrients from the soil under low soil temperatures. This can be alleviated by inoculating the plants with arbuscular mycorrhizal [AM] fungi in the greenhouse growth phase. These are naturally-occurring soil fungi that form a beneficial symbiosis with the roots of plants, assisting them with nutrient uptake from the soil. However, two weeks in the greenhouse limits the opportunity for the AM fungi to become established- a process that can take 10 days under optimal conditions. We conducted experiments over three successive years to test the hypothesis that if the AM fungus-inoculated horticultural potting mix in which the sweet corn seeds were to be sown was first incubated in the greenhouse for one week prior to sowing the seeds, subsequent development of the AM fungus colonization of roots would be greater than if the seeds were sown in freshly-inoculated potting mix. Indeed, percentage of root length colonized by AM fungi and overall colonized root length were greater in seedlings grown in the pre-incubated potting mix. The higher level of colonization was equivalent to that produced when seedlings were inoculated with an 80% higher population of AM fungi in the potting mix. Pre-incubation of greenhouse flats containing AM fungus inoculum for one week in the greenhouse prior to sowing vegetable crops results in enhanced development of the mycorrhizal symbiosis in the subsequently grown seedlings. Technical Abstract: 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 potting media used for 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 deg. C incubation to inhibit spore germination prior to sowing seeds and compared to colonization 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 flats of potting media proved to be an effective way to enhance formation of mycorrhizas. |
