Issue link: https://read.dmtmag.com/i/787641
12 FEBRUARY 15, 2017 GOOD FRUIT GROWER www.goodfruit.com associated with multiple genes, Norelli said. Once that locus — a location on a chromosome — was identified, WSU researchers built a DNA test to assess which seedlings inherited the resistance gene. The grow- ing library of DNA tests means that Norelli's seedlings can also be screened for about 10 other desirable traits, such as acidity and skin color, Peace said. In traditional breeding efforts combining two already high-quality cultivars, fewer DNA tests are usually needed, but "there's a lot more bad genetics in this mate- rial from the wild apple," Peace said. Using all the tests on each generation of seedlings helps to weed out those unwanted wild genes faster. Before DNA tests, breeders measured disease resis- tance by purposely infecting new trees. But having access to the genetic markers is a huge advantage, especially for a disease like blue mold, which causes fruit decay during storage rather than damages the tree itself. "For a lot of diseases like scab and fire blight, we can screen seedlings directly with the pathogens, but DNA tests are better. And one of the big advantages of DNA markers for fruit traits is it saves us years versus waiting for apples," Norelli said. To speed up the breeding process even further, Norelli is using a genetically modified apple that carries a gene from a birch tree that initiates early flowering. By using it as a parent, his trees are blooming and ready to breed at just over a year old, instead of having to wait three years for each generation to flower. That transgene for early flowering was introduced into the Pinata cultivar by German researchers, who used it in a similar way to breed fire blight resistance into modern cultivars as part of the FruitBreedomics project. The early flowering trait comes from a single, dominant gene, which means that every generation, half the seed- lings produced are early flowering; the other half flower normally because they did not inherit the chromosome with the transgene. To accelerate this breeding process, Norelli crossed the parents — the offspring of the wild apple and the Royal Gala and the Pinata cultivar containing the birch tree gene — in the conventional manner and selected off- spring with both the resistance gene and the early flower- ing gene. Now, he is continuing to cross those offspring for several more generations to weed out unwanted wild apple genes. Once that breeding process creates high-quality, blue mold resistant cultivars, Norelli will no longer need the early flowering gene. So in the final round of the breed- ing process, he will select offspring that don't carry the transgenic gene from the birch tree — and thus are not considered genetically modified — to grow into normal apple trees. Testing the test The second generation of blue-mold resistant, early flowering apple trees are growing in the U.S. Department of Agriculture greenhouse in West Virginia. Some of the spindly trees are already fruiting. But even high-tech tools need to be proven in the nursery. So, Norelli is preparing to test the DNA-based breeding by exposing the first crop of fruit to the blue mold fungus, so he can evaluate how susceptible they really are. "We are validating whether that test actually predicts resistance. That's really important because before we at RosBREED release a tool, we test it so breeders can use it with confidence," Norelli said. If the test proves itself, as scientists suspect, the cul- tivar should be ready for breeders by 2019. There are a few more crosses to go, Norelli said, to maximize the domestic apple genes and minimize the wild genes. To meet that deadline, the team is employing one more novel genetic tool that helps to select seedlings with the least wild DNA. Every new generation has a mix of its parents' traits — typically 50-50 — but due to some genetic rearranging that happens as chromosomes are passed on, there's always a little variation. "By the third generation, about 25 percent of the genetics should be M. seversii, but because of crossing over of the chromosomes, some have less and some have more," Norelli said. "We're using a DNA test to track how much wild DNA is left." FruitBreedomics developed the test to track apples' lineage by looking at about 20,000 loci. That's far from sequencing the entire genome, but it provides a signifi- cant snapshot of an apple's 17 chromosomes. After the test is run on each parent — the wild apple, Royal Gala, and Pinata with the early flowering gene — the offspring can be compared to see how much they still resemble the wild apple. With that insight, Norelli can beat the 50-50 odds slightly with each cross and select those seedlings with both the key traits and the least wild DNA to give rise to his next generation. "With the accelerated system, that should be a one- to two-year window to get that next generation," he said. "Our first objective is to produce elite breeding parents with resistance alleles and then trying to incorporate other resistance alleles for fire blight and scab." • "We are tapping into the latest advantages that have been made in genomics science to really advance the efficiency of apple breeding." — Jay Norelli Biopesticides. Short REIs and zero days to harvest. Resistance and residue management. Application flexibility. Better harvest management and timely shipping. Recommendations: Cueva, Kocide Integrated copper solutions for season- long fire blight and summer disease control Double Nickel Broad spectrum foliar powdery mildew and fire blight disease control OSO FRAC 19 fungicide for summer diseases and post-harvest protection CYD-X HP, Madex HP Codling moth and Oriental fruit moth control PFR-97 Broad spectrum insecticide and miticide Neemix Insect growth regulator for psyllid control Deliver Bt for leafroller larvae control Screen Duo For sunburn protection and heat stress reduction LifeGard First biological activator. Triggers Induced Resistance (IR) Diseases and Pests: Fire blight Codling moth, Oriental fruit moth Powdery mildew Psyllids, aphids, mites, leafrollers Summer diseases and post-harvest rots 1-800-250-5024 • www.CertisUSA.com ©2017 Certis USA DN Cu K2 K3 PFR Ma De LG Nx SD O CX