Courtesy Washington State UniversityScion, grown using tissue culture, is grafted onto rootstock, also produced with tissue culture.Micrografting, which relies on tissue culture to grow clean rootstock and scion, could cut the time it takes to propagate cherry trees by one-third to one-half compared with open-field nursery production
Washington State University undergraduate Matthew Allan had seen his father order cherry trees from nurseries two and three years out, only to have the delivery reduced because of weather or other problems, according to a news release.
Working under assistant professor Amit Dhingra, Allan explored whether bringing propagation into the lab in the form of tissue culture would reduce the risk.
Dhingra said his goal was to see if it were possible to develop an orchard-ready tree in a year compared with the typical two to three years for open-field nurseries.
Allan and graduate student Tyson Koepke sterilized buds collected from dormant rootstock trees.
They then placed them in growth medium that contained nutrients and plant hormones to promote cell division.
Eventually they planted the small trees in soil.
About 16 to 20 weeks after placing the callus in the medium, the rootstock was ready to graft.
The two propagated scion varieties similarly, although they weren't transplanted into soil.
Allan snipped off the top of the scion, grafting it onto the rootstock.
In the future, Allan said he thinks having both the scion and rootstock at the same growth stage would work better.
Dhingra would like to incorporate mist beds—high-humidity growth chambers that speed graft union healing—into the process.
With this technique, nursery growers could possibly produce three to four cycles of trees each year, according to the release.