Molly Bergum


Assessing Cold Hardiness of Two Kiwiberry Species by Microscopically Comparing Cold Damage in Developing Buds

Kiwiberries are a minor horticultural crop comprised of multiple species in the Actinidia genus. Actinidia arguta and A. kolomikta, both of which are experimentally grown at the University of Minnesota Horticultural Research Center in Victoria, MN, are considered more cold hardy than most species in the genus. During a polar vortex in January 2019, Victoria experienced lows of -29°F, which were predicted to be lethal or nearly lethal to many kiwiberry varieties. This project aimed to understand how the extreme cold affected cellular structures in developing buds of A. kolomikta and A. arguta. Buds from two varieties of A. kolomikta, which were expected to be tolerant to the cold, were collected after the polar vortex. Additionally, buds from three varieties of A. arguta were collected before and after the polar vortex. All buds were preserved and embedded in paraffin wax. Samples were sectioned with a microtome, stained with Toluidine blue, and analyzed with light microscopy. A. arguta samples often featured fissures immediately below the bud, which could prevent extracellular ice masses at the crown from entering the cells within the bud. Unlike the A. arguta samples, both A. kolomikta samples were intact, and cells within the pith tissue included darkly stained bodies, which are likely saccharides that play a role in cold hardiness. Although the sample size in this study is too small to draw statistically important conclusions, observations provide fundamental insight for future research about mechanisms of cold hardiness in kiwiberries. 

Video file