Cold-hardy kiwifruit breeding research underway

U Fruit growers try to develop kiwi that will thrive in Minnesota’s climate.

by Carter Haaland

Fruit growers at the University of Minnesota Horticultural Research Center near Victoria, Minn., are growing cold-hardy kiwifruit. Though the facility is best known for apples and grapes, they are making an effort to develop lesser known fruits, said Jim Luby , a professor in the department of horticulture. âÄúRelative to other small fruits, kiwifruit is kind of almost the neglected stepchild,âÄù Bob Guthrie , a volunteer curator at the center, said. Most of the work in the kiwifruit breeding project is actually done by Guthrie. âÄúBob is âĦ the driving force behind this whole kiwi project,âÄù said Steve McNamara , a scientist in the Woody Landscape Plant Breeding and Genetics program. Guthrie is one of the top experts on cold-hardy kiwi in the United States, Luby said. Guthrie started volunteering at the center 16 years ago, coming into the project without a background in horticulture. While he does spend time at the center, he does most of the actual crossing of kiwifruit at his home. Kiwifruit are pretty easy to cross compared to many other plants, Guthrie said. He uses doughnut bags to cover the blossoms because the wax paper sheds rain. Once the blossoms open up, he uses a watercolor paint brush to pollinate them. After a week, he checks to see if the cross took. Sometimes Guthrie brings kiwifruit cuttings to the center because there is more space for them to grow. He can also test their hardiness with a special freezer McNamara helped him set up. Guthrie can test kiwi stem selections by putting them into a controlled freezer and then exposing them to various test temperatures to see how well the selection is adapted to the Minnesota climate, McNamara said. Kiwifruit are relatively easy to grow because they do not have many pests or diseases, Luby said. He has been impressed with how free of disease they are. âÄúItâÄôs hard to grow an apple without bugs in it,âÄù he said. Kiwifruit have a long history in the state. The fruit has been around in Minnesota for about three centuries, Guthrie said. Horticultural professor Samuel Green was growing kiwi on the St. Paul campus around 1892. However, the kiwi were not cold-hardy enough to do well in MinnesotaâÄôs climate. The fruit had its brush with fame in 1923 when Alexander Graham BellâÄôs son-in-law, David Fairchild, made the first documented cross of two species of kiwifruit, Guthrie said. The center near Victoria started growing them in the mid-1980s on a five-wire grape trellis, which was about 250 feet long. There are about 80 different species of kiwifruit, with significant variations. The kiwis Guthrie works with have many different colors of flesh, including green, yellow, orange, red and purple. Guthrie works with about a dozen of these species. Arguta , polygama and kolomikta are the three most cold-hardy species, but kolomikta is by far the hardiest, Guthrie said. All three could be grown safely in the Twin Cities area most winters. Their common names are Bower Berry, Silver Vine and Arctic Beauty, respectively. âÄúMost of the cold-hardy species are fuzz-less âĦ so you eat them like a grape,âÄù Guthrie said. Luby said he prefers the taste of the centerâÄôs kiwi to those found in stores, citing their added sweetness and slightly spicy, almost cinnamon-like flavor. They are now trying to figure out how to grow kiwi on a large enough scale that fruit growers could grow and sell them, Luby said. A new trellis, which will hold about 500 plants, was finished recently. One of the greatest annual costs of kiwifruit is pruning, but this does not worry Guthrie. âÄúI think thereâÄôs a kiwifruit in your future,âÄù Guthrie said.