Benjamin Hoose and Faculty Mentor: Matthew Madsen, Plant and Wildlife Sciences
Sagebrush seed agglomerates (referred to as ‘agglomerates’ in the remainder of the report) are small balls of seed, clay, and compost that allow us to treat sagebrush seeds with germination enhancers. The goal of my project was to determine whether we could use the antimicrobial properties of juniper wood to reduce fungal attack of sagebrush seed by replacing the compost component of agglomerates with ground juniper. We met our goal, and determined that juniper wood does not act as an effective fungal deterrent. However, we did successfully incorporate juniper into agglomerates, which added consistency and repeatability to the agglomerate recipe by replacing the variable compost component. We also made an important discovery involving an interaction between one of our germination enhancers and other components of our seed coating recipes.
We began our study using bluebunch wheatgrass seed as a model to test the potential fungicidal properties of juniper. We chose to use bluebunch wheatgrass first because the seeds are much larger, so fungal attack is easier to observe, and we knew that fungal attack is a significant source of mortality for those seeds. We coated the seeds with a glue-like polymer binder and either lime or ground juniper. We added commercial fungicide to some of the lime-coated seed for comparison. We also added abscisic acid (ABA) to half of the seeds. ABA is a plant hormone that delays germination to ensure that seeds germinate in spring rather than in the middle of the winter. We hypothesized that adding ABA would give fungal pathogens more time to attack the seeds. We further hypothesized that ground juniper would improve germination in a similar way as commercial fungicide.
We found that ground juniper did not significantly improve germination as commercial fungicide did. However, we discovered that ground juniper nearly doubled the delay in germination caused by ABA compared to lime (see Figure 1). We hypothesized that some of the abscisic acid (ABA) was being neutralized by the powdered lime because lime is alkaline. We tested the pH of juniper, and found it to be slightly acidic. We conducted another experiment to test the effect of the powder in seed coatings on ABA.
We used a variety of coating powders with differing pH to test the effect of coating powder pH on ABA. Some of the powders we tested include juniper, lime, diatomaceous earth, and talc. We found that the pH of the coating powder is a major predictor of germination delay caused by ABA. Acidic powders produced more delay than alkaline powders, with a predictable gradient in between the extremes of pH.
The discovery that seed coating powders interact with seed treatments was an important development. Lime is commonly used in seed coatings, but researchers should be careful using it with acidic seed treatments. ABA did not produce the delay we expected in our field trials this year. Replacing the lime component of our seed coatings could increase the delay.
Though we have not produced enough data surrounding this finding to produce a publication, we have been able to present the data at various meetings for funding and correlation purposes. The data could be incorporated into a publication about ABA seed treatments in the future.
It is possible that ground juniper does have some antifungal properties useful for improving germination, but that our tests were not sensitive enough to show a significant treatment effect. We could test this hypothesis by increasing the number of repetitions, or by increasing the sensitivity of the test. Increasing repetitions is expensive, so we have begun work developing a fungal inoculation method to increase the sensitivity of our tests. If we are successful, this study could also produce a publication.
We concluded this project by incorporating ground juniper into sagebrush agglomerates. We found that sagebrush agglomerates made with juniper had significantly higher germination than untreated sagebrush seed. However, agglomerates made with ground juniper did not have significantly higher germination than agglomerates made with compost. We concluded that ground juniper is a suitable replacement for compost in the agglomerate recipe. This finding will help other researchers to be able to repeat our research involving agglomerates, and help seed coating companies to be able to produce agglomerates in bulk for land manager use.
Though ground juniper did not manifest the antifungal properties that we expected, we made valuable discoveries as a result of this project. We learned that ground juniper is a better seed coating powder than lime for use with ABA. The same may be true of other seed treatments, which has broad-scale implications. We also learned that ground juniper can replace compost in the agglomerate recipe, which will be useful for further research and field application.