acer freemanii

Not Just Sugar Maples – Part I

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Ohio Maple Days 2022 did not disappoint.  The food was fantastic, the vendor room crowded, and the presenters shared a wealth of knowledge of expertise across a wide range of subjects.  I was among those speakers, and Abby van den Berg and I presented a pair of talks that focused on those other maples.  Abby’s perspective from Vermont and focused mainly on pure red maples (come back for Part II next week for those highlights), and my perspective sharing from the basis of our ACER-funded research on Acer freemanii, Freeman’s maple, or just “rilver” for short.  Before we get into it, be sure to mark your calendars for next year’s conference December 8th and 9th!

Let’s try this recap in a series of short statements.

1) Sugar maples are the gold standard for maple syrup production – there is no disputing that.

2) But other maple species probably deserve more love than they have traditionally been given.

3) Mounting pressures from climate change, forest pests, and a host of other reasons make other maple species more important to consider than ever before.

4) Because of the above, it makes sense to learn more about other maple species production potential.

5) We thought we had simple (red x silver) hybrid maples in the OSU Mansfield research sugarbush where we have our single-tree research stations.

6) We thought wrong.  Turns out the hybrid maples are more mysterious than that – stay tuned for further genetic testing!

7) Regardless of what other variety of maple we are working with it still made sense to compare their production potential and other characteristics to sugar maple.

8) Research began in the 2021 as we pulled over 20 sugar maples and 50 of the mystery maples into single-tree sap collection chambers that measured daily performance.

9) Research techs and research PI quickly learned that maple research can be icy cold!

10) The 2021 season was historically bad and we had 5 roller coaster runs total.

11) During the 2021 season, our mystery maples were not as sweet overall as sugar maples, however, the mystery maples held a more stable Brix level from the start of the season to finish.

12) Mystery maples lost ground to sugar maples in terms of sap production volume as the season got later and later.

13) Surprised yet?  Maybe not.  But consider this – the best half of our mystery maples OUTPERFORMED the worst half of our sugar maples in terms of syrup production potential.  Would that also hold true for 2022?

14) Fast forward 11 months to yet another choppy, wild, and erratic 2022 sap season.  When will we have another “normal” sap season?

15) Note to self, might have to add another 10 degrees to y-axis of Sap Run graph in 2023.  I surely hope not!!

16) More in line with studies elsewhere, our 2022 mystery maple trial trees matched or outpaced sugar maple’s sap volume production up until the final sap run of the year.

17) Brix consistently tracked 0.2-0.4 points below for mystery maples as compared to sugar maples.

18) Ultimately, we’re excited and hopeful for a “normal” 2023 season to collect data from a more representatively average season.

19) In the interim, both years suggest that mystery maples are not to be overlooked especially if you are an operator using reverse osmosis in your sugarhouse looking to expand your number of taps.

20) Stay tuned for 2023 – our 3rd year of ACER-funded research investigating alternative maple species production potential.

ACER Research Update: June 2021

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We are continuing to make progress on our ACER grant “Freeman’s maple (red x silver) potential for syrup production and resilience in Ohio’s forests.”  Earlier in the month, we collected a series of reference samples from Secrest Arboretum and other locations of pure red maples, pure silver maples, and Freeman’s maples to dial in our approach for identifying individual trees in the Ohio State University-Mansfield research sugarbush via genetics.  The Molecular & Cellular Imaging Center at Ohio Agricultural Research and Development Center (OARDC) in Wooster is processing the tissue samples in order to refine our genetic markers that are particularly useful for pinpointing hybridity of the Freeman’s or “rilver” maple.

How does one use genetics to identify different species or hybrids between two species?

Labs can slice out key segments of the DNA chain from extracted genetic material from plant cells, tissues, and seeds.  Once the right part of the DNA chain is isolated, a process called amplification copies and replicates the genomic material to make the diagnostic markers easier to interpret.  Polymerase chain reaction (PCR for short) is the most common method of amplification.

Try thinking about amplification this way.

You have no doubt used a photocopier in the past.  PCR is just a biotechnology copying machine.  Just as you might use your office equipment to make 100 copies of a single page out of a big book, PCR allows you to make copies of only the DNA piece that holds the information of interest.  There is one key difference (among many!) between your normal office copier and this biotech PCR process though.  A copier makes a stack of copies 1, 2, 3, 4, …97, 98, 99, and 100.  PCR makes copies more efficiently, exponentially actually – 1, 2, 4, 8, 16, …128, 256, 512, so on and so forth.

Enough about amplification, what can we do with diagnostic markers once we have made a whole bunch of duplicates.  Genetic markers are essentially genetic fingerprints.  The unique segments of DNA – the genetic fingerprints – differentiate different species from one another or show varying degrees of hybridity.  These fingerprints can be visualized with another lab process called gel electrophoresis.  Another big word, apologies.  But the main point is this – gels allow us to see, actually see with the naked eye, the genetic fingerprint of our sample and allow us to decide which species or hybrid we are examining.

Above is a panel of genetic fingerprints for differentiating silver maple on the left and red maples on the right.  The image was published as part of a study in 2019.  You can see that silver maples on the left are characterized by two bright bold lines at the bottom of the panel and a third almost halfway up.  Red maples, on the other hand, share the top and bottom band with silver maples, but have a different unique fingerprint with the second marker landing halfway in between.

Enough Genetics 101 for now…the ACER research continues to progress, and we are working toward a more reliable way of understanding how much red versus silver maple genetics are in our “rilver” research maples.

Author: Gabe Karns, OSU Mansfield & SENR