Developing Christmas Trees with the Help of the CytoSAVER Controlled-Rate Freezer

User Case Study

At Strex, we strive to gain valuable perspectives on our clients’ applications. The following is a case study of one of our clients, Andrew Schofield, the lead genetics and plant biology consultant at the Christmas Tree Council of Nova Scotia in Canada, and an instructor and technician in the Biology Department at Acadia University (Wolfville, NS). He graciously shared with us his experiences leading up to his work with the CytoSAVER Controlled-Rate Freezer. Our interview with him has been edited for formatting.

The balsam fir features a variety of traits that make it a beautiful, fragrant Christmas tree

The Christmas Tree Council of Nova Scotia is developing clonal lines of the balsam fir, a species of evergreen tree bred for characteristics that make it the ideal Christmas tree. While the breeding process is difficult, there are opportunities for optimization. The CytoSAVER Controlled-Rate Freezer can help maximize the efficiency of the cryopreservation steps of the process, helping to advance Canada’s balsam fir breeding programs.

What kind of research do you focus on at the Christmas Tree Council of Nova Scotia?

The balsam fir (Abies balsamea) is a species of conifer, or evergreen tree, native to Canada that is known for its fragrance and architecture. These traits have made the species stand out as the ideal Christmas tree and positioned it as the star atop Canada’s agricultural pride. Andrew Schofield and his research team are taking on the difficult task of developing these traits as part of the Christmas Tree Council, a volunteer organization that is funded by the Province of Nova Scotia. The Council has been a driving force in the tree-growing industry for decades, collaborating with both government and academic institutions. As Andrew puts it, “they’re doing a lot of great work for the growers in multiple different projects,” focusing on soil health, tree fertility, nutrition, cost management, and marketing solutions. Before joining the Council as a consultant, Andrew used his skills in molecular genetics to interrogate genes expressed in different tree lines, and how they interacted with each other.

What challenges have you faced in your research?

Conifer breeding is an unusually difficult process, and many tree combinations must be bred and field-tested over the course of decades. The Christmas Tree Council is looking for methods to make the process faster and more efficient. Cells at various stages in the balsam fir’s embryonic development can be frozen for long-term storage and preserved until field testing. “You take seeds of trees that you really like, breed them, and initiate somatic embryo lines. You cryopreserve the lines at the same time you produce seedlings to put into field trials. And then after 10 years, you have a pretty good idea about how all those lines are performing,” Andrew explains. “People have used this technique for spruce and pine around the world. I think we’re the first to do it in balsam fir.” Freezing these cells, however, must be done in a controlled manner to avoid sacrificing the feasibility of the balsam fir embryos.

How do you envision the CytoSAVER Controlled-Rate Freezer helping you in your research?

Andrew is hoping that controlled-rate freezing technology like the CytoSAVER may facilitate the balsam fir breeding process by maximizing cryopreservation throughput and turn-around time. With a capacity of up to 171 vials (2 mL), the CytoSAVER is capable of freezing samples, like conifer embryos, from room temperature to -80 °C in under 2 hours. The freezing protocol can be run at a controlled rate to maintain the viability of conifer embryos, and the CytoSAVER’s built-in heater can warm it back up to room temperature quickly to reduce downtime between freezing cycles.

CytoSAVER

The liquid nitrogen-free CytoSAVER Controlled-Rate Freezer can help maintain cell viability during the cryopreservation process

High-throughput cryopreservation is crucial for Andrew’s projects. “As it turns out you need a little bit of luck,” he explains. “The initiation rate for fir is around 1%. It takes a lot of work to get a number of lines up and ideally you want to pick from several hundreds of lines to find ones that are really good. It takes a while to build up that number and having a good, reliable cryopreservation technique is key.” Andrew was looking for a solution with which he would be sure that hundreds of conifer samples could be frozen without risking cell death, as often happens with uncontrolled or ‘flash’ freezing. Uncontrolled freezing causes ice to form inside a cell and expand rapidly, rupturing the membrane and destroying the cell. “That’s why I wanted to use something like the CytoSAVER, because I want to know what’s going on in the tube,” Andrew continues. “With simpler methods, you just stick it in a little tub, put it into -80 °C and hope that it all goes well. If we’re doing this big project, we’re gonna get a freezer that we know what’s going on.” With the CytoSAVER’s user-friendly temperature logger, Andrew will get accurate temperature reporting throughout the freezing process. This improved efficiency also has benefits downstream. “If things go well, we might generate 50 lines a year. If you do find a line that you like that grows well in tissue culture and that performs well in the field, then it has a lot of potential to really improve the industry for our growers and help the local agriculture.”

The CytoSAVER can freeze samples without having to use liquid nitrogen, which can be dangerous to handle and cost-inefficient to maintain. “It was going to be pretty expensive to have a nitrogen supply on hand, and whether you use it or not, it’s going to evaporate,” Andrew says. This was a key factor in his decision to incorporate the CytoSAVER in balsam fir cryopreservation. “Not having to worry about having a nitrogen source really was a big factor for us in terms of why we chose it.” Without needing a liquid nitrogen connection, the CytoSAVER is also more compact and portable, which means it can be installed on a standard benchtop and easily moved around as needed. The CytoSAVER Controlled-Rate Freezer is ideal for a wider range of cold chain workflows and environments.

What does the future hold for your projects, both near and far?

Through its collaboration with Nova Scotia Community College, the Christmas Tree Council is setting up a large laboratory where the CytoSAVER can be used for multiple tissue culture applications. “The whole breeding program research can happen in one place. Not all industry groups have a research branch like this. It’s certainly unique for breeding,” Andrew excitedly tells us.

The Council is developing a breeding program that will produce balsam fir clones with desirable traits and predictable breeding timelines. Andrew envisions a clonal line with which, “you know when to harvest them, how long they’ll keep their needles after harvest, the timing for when the needles flush out of the bud. You can really benefit the growers by developing lines that have certain beneficial traits, including the aroma, length of the needles, and the overall architecture of the tree.” He is looking forward to the CytoSAVER being an integral part of this project. “The goal over the next few years will be to initiate and cryopreserve around 300 lines of somatic embryos from excellent parents, and initiate seedlings from all those lines and get them into field trials.”

The Christmas Tree Council of Nova Scotia develops clonal balsam fir lines to make the perfect Christmas tree

With a focus on the future, Andrew is working on the post-harvest process, supporting funding applications, and bringing together tree growers and researchers to tackle the emerging challenges of their field. “Every partnership brings in more and more experts, and that’s exciting to me,” says Andrew. “We have really great funding for the next 3 or so years from the government of Nova Scotia and from the Natural Sciences and Engineering Research Council of Canada, among others.” One of the biggest challenges the Christmas Tree Council will address is preparing the balsam fir to take on its biggest threat. “Climate change has this bigger and bigger effect in Nova Scotia,” Andrew warns, emphasizing the importance of reproducing beneficial traits in the balsam fir and accelerating tree improvement. He highlights cryopreservation of desired trait-expressing embryos as a key tool that, “might really be necessary if you’re trying to combat some of the very real effects of climate change.”

The team at Strex would like to thank Andrew Schofield at the Christmas Tree Council of Nova Scotia for taking the time to share his story with the CytoSAVER Controlled-Rate Freezer. Click here to learn more about the CytoSAVER or Strex’s other products. Feel free to reach out to our support team and see how we can help you set up your cryopreservation and cold chain workflow, or click below to request a demo of our products.