Issue link: http://read.dmtmag.com/i/560612
www.goodfruit.com GOOD FRUIT GROWER SEPTEMBER 2015 29 Evans also plans to make new crosses. She has a range of germplasm at WSU's Sunrise Orchard in a pear rootstock parent collection she established five years ago. Having good material to cross is the key to start- ing a breeding program, she said. Most of this material came from the pear collection at the National Clonal Germplasm Respository at Corvallis, Oregon. Evans spent some time walking around the collection looking for interesting species. One that she picked out was Farmingdale, which, though not dwarfing and not a par- ent of OHxF 87, does have high resistance to fire blight. "One of the nice things about Pyrus is it's quite diverse, and for the most part willing to cross pretty well," she said. "There's an awful lot of opportunity to bring in some germplasm that would suit this industry." A benefit of using what she calls "slightly exotic germ- plasm" is that it can introduce other important charac- teristics, such as resistance to fire blight and tolerance of pear decline, as well as dwarfing. Longer process Breeding new rootstocks tends to be a longer and more difficult process than breeding varieties, Evans said. That's because rootstocks can't be crossed until they grow into trees and bloom. Also, it's more difficult to evaluate the growth characteristics of a rootstock than to spot an exciting new apple growing on a tree. The differences are more subtle. "My personal view is the amount of testing you should do of a new rootstock is more than for a new scion because if you make a mistake and release a new rootstock out to the industry, it can have a much more devastating long-term consequence than a new scion," she said. Advanced selections need to be tested with different scions and in different growing conditions, and she likes to collect at least six or seven years of data from trials. "What inevitably happens is you have to go through a few rounds of that to cut the numbers down," she said. That's why on-going support by the pear industry was important. "I wanted to start this with a reasonable level of com- mitment from the industry that they would be prepared to look at this in a long-term way," Evans said. "It's a waste of everyone's time, effort, and money to go through the very early part and not follow through." Figuring out how best to multiply any promising selections for replicated trials will be part of the project. Dhingra, who is collaborating with Evans, brings expertise in tissue culture and micropropagation. Genetics Genetic markers enable scientists to identify traits in plant DNA from young seedlings without needing to grow a whole tree, but markers will not be developed for the project initially. Evans said some markers have been identified for the dwarfing trait in apples and she and her colleagues plan to see if those might work in pears, since the fruits are related. Dr. David Neale, geneticist at the University of California, Davis, is working on a project jointly funded by the Northwest and California pear industries to assess the genetic variation of pears in the national repository in Corvallis, Oregon. The genetic data will be overlayed with the visible, or phenotypical, variations observed between the pear species. "Long term, we're trying to do more and more phenotyping of the collection so we can potentially develop more DNA-based tools to help us with breeding selection," Evans said. Neale, Dhingra, and Evans are part of a Pear Genomics Research Network created about two years ago to coordi- nate the various research efforts relating to development of pear rootstocks. Other scientists involved include Dr. Richard Bell and Joseph Postman with the USDA ; Rachel Elkins and Dr. Pedro Martinez-Garcia at UC; Dr. Stefano Musacchi at WSU; and Dr. Todd Einhorn with OSU. Einhorn is heading a project to evaluate elite pear root- stock material, including quince and Amelanchier selec- tions (see "Promising pear rootstocks," April 15, 2015, Good Fruit Grower). Both quince and Amelanchier are pome fruits. Some of the best selections will be planted in replicated trials in Washington and Oregon. • Consider for your next planting: • BRUCE PONDER • SUSAN WILKINSON • ADAM WEIL • DAVE WEIL 503-538-2131 • FAX: 503-538-7616 info@treeconnect.com www.treeconnect.com BENEFITS: • Disease tolerant • Cold hardy • Adapts well to all cherry-growing districts • Forms flower buds and comes into bearing quicker than Mazzard with a better distribution of flower buds Now booking orders for 2016 Call Tree Connection: 800-421-4001 Dwarfing Cherry Rootstock Krymsk ® 5 Krymsk ® 6 [cv. VSL-2, USPP 15,723] [cv. LC-52, USPP 16,114] "Krymsk ® 5 and Krymsk ® 6 cherry rootstocks have proven to be the best rootstock for our orchards. They are yield efficient, grow and adapt well, and are cold hardy." —John Morton The Dalles, Oregon