Deliverable #1: Knowledge – parentage refuted and deduced for WSU C7 [coded]

To Whom: Kate Evans, pome fruit breeder, Washington State University

Story: The Washington Apple breeding Program (WABP), begun in 1994, uses scores of parents, has advanced more than a hundred numbered selections, and has generated many tens of thousands of seedlings. Controlled crosses are made, but not all pedigree records are correct, as contaminating pollen can sneak in and plant labels sometimes get mixed up. Selection WSU C7 was identified as having several excellent attributes after years of phenotypic evaluation and eventually advanced to “elite” status in 2010. But its parentage records of ‘Hatsuaki’ × ‘Cripps Pink’ were shown to be incorrect based on genotyping with two SSR markers at the Ma locus. In fact, the selection’s allelic combination didn’t match either recorded parent. But two alleles were a match with a specific rare haplotype (believed to partially contribute to excellent crispness, juiciness, and tartness) found in only one commonly used WABP parent and its offspring: ‘Honeycrisp’. The other haplotype is a common one with many possible donors. WSU C7’s parentage was updated to ‘Honeycrisp’ open-pollinated.

Deliverable #2: Knowledge – “fresh sensation” genetic potential for new parents

To Whom: Kate Evans, pome fruit breeder, Washington State University

Story: The WABP’s advanced selections are not only candidates for new cultivar releases, but also represent possible parents to help aggregate valuable alleles into the next generation of superior cultivars. Two SSRs at the Ma locus associated with “fresh sensation” traits of tartness, crispness, and juiciness were used to obtain predictive functional genotypes of WABP parent cultivars and selections. This SSR genotyping has already been used to identify several elite selections with valuable alleles to use as parents.

To Whom: Kate Evans, pome fruit breeder, Washington State University

Story: The young WABP has now officially released three cultivars. The most recent, ‘WA 38’, was released in early 2012 and is currently being mass-propagated to provide commercial-scale planting material. ‘WA 38’ is exceptionally crisp and juicy all year round and has spritely tartness – a fresh sensation with every bite! This crispness and juiciness are believed to be due at least in part to a ‘Honeycrisp’ haplotype that ‘WA 38’ carries at the Ma locus inherited from its confirmed father, ‘Honeycrisp’. The expected orchard performance of this new cultivar is therefore partially predicted by DNA-based information from RosBREED – and soon the public will be able to enjoy the great taste of ‘WA 38’ while benefiting from the nutritional goodness of apples!

Deliverable #4: Tool – DNA test of “fresh sensation” for routine seedling screening

To Whom: Kate Evans, pome fruit breeder, Washington State University

Story: An SSR-based DNA test targeting the Ma locus helps predict trait levels for tartness, crispness, and juiciness. Prior to RosBREED, this was a crude tool. The test has since been refined using large-scale multi-location phenotypic evaluations conducted across three breeding programs, now in their third season, combined with SNP-based genome-scanning. The DNA test originally used two SSRs, while now we use just one. This SSR marker is easy to run and score and very cost effective – vital features for screening thousands of WABP seedlings each year.

Deliverable #5: Germplasm – new families in breeding nursery with superior genetics

To Whom: Kate Evans, pome fruit breeder, Washington State University

Story: Following crossing and obtaining seed in 2011, more than 5000 germinated seedlings from seven families had their DNA extracted and were screened in 2012 with the DNA test described in Deliverable #4. The DNA-based technicalities took place in the Washington Tree Fruit Genotyping Lab in Pullman, WA. Selecting only those seedlings with superior “fresh sensation” genetics, Kate reduced the family sizes by more than half. About 2000 seedlings were then moved to a nursery where they’ll be bud grafted in 2013 and then planted in the breeding orchard in 2015. The creation and crafting of these families was therefore guided with RosBREED’s polished Ma locus DNA test.

To Whom: David Bedford and Jim Luby, apple breeders, University of Minnesota

Story: Many breeding program selections from the UMN breeding program were genotyped with the IRSC 8K apple SNP array v1 and with SSR markers as part of the RosBREED Crop Reference and Breeding Pedigree sets. Knowledge of their genotypes was used in the 2011, 2012, and 2013 crossing seasons to enable decisions about smarter ways to use them in crosses, combining knowledge of their phenotypic performance with their expected breeding value based on genotyping for traits such as flesh texture, skin color, and apple scab resistance. They also used the information on parents used in 2012 matings to decide which seedling families should be screened following seed germination in 2013 and devise strategies for which seedling types to discard or receive separate treatment as they are moved into seedling orchards.

To Whom: Matthew Clark and Cari Schmitz, graduate students, University of Minnesota

Story: The IRSC 8K apple SNP array v1 has had application beyond genome scanning of the RosBREED reference germplasm sets. UMN graduate students (and RosBREED breeding trainees) conducted additional genome scans of individuals in pedigree-linked populations derived from ‘Honeycrisp’ to develop an accurate linkage map of SNP markers for this cultivar that has been extensively used in U.S. breeding in recent years. They then used their ‘Honeycrisp’ linkage map as input data for another RosBREED tool, FlexQTL™ software, and combined it with phenotypic data, to identify and characterize important loci for flesh texture and apple scab resistance.

To Whom: David Bedford and Jim Luby, apple breeders, University of Minnesota

Story: UMN breeders used knowledge, developed by breeding trainees Cari Schmitz and Matthew Clark, of the expected breeding values of UMN selections derived from ‘Honeycrisp’ for flesh texture and apple scab resistance to help decide which MN selections to use in 2013 crossing and how they should be mated with other parents.

To Whom: Amy Iezzoni, tart cherry breeder, Michigan State University

Story: A significant delay in bloom time has the potential to reduce the risk of crop loss to spring freeze events. Three chromosome regions were identified that contain genes that control bloom time. These regions are on chromosomes 1, 2, and 4. Knowledge of what parents contain these late blooming alleles was used to design crosses made in spring 2013.

Deliverable #10: Knowledge – parents contributing desirable fruit flesh color alleles

To Whom: Amy Iezzoni, tart cherry breeder, Michigan State University

Story: The tart cherry industry in the U.S. is based on a cultivar that has a desirable brilliant red color. A region on chromosome 3 associated with fruit color was identified. Knowledge of what parents contain the desirable fruit color alleles was used to design crosses made in spring 2013.

To Whom: Amy Iezzoni, tart cherry breeder, Michigan State University

Story: Any new tart cherry cultivar would be more likely to be adopted in the U.S. if the maturity date was later than that for the standard cultivar, ‘Montmorency’. A genomic region was identified on chromosome 4 associated with genetic variation for maturity date. Alleles contributing to early and mid-season maturity were identified and the parents included in the RosBREED tart cherry set carrying them were determined. These alleles can now be specifically selected against in crossing decisions.

Deliverable #12: Tool – identification of large fruit size alleles in hybrid seedlings

To Whom: Amy Iezzoni, tart cherry breeder, Michigan State University

Story: The wild small-fruited species P. canescens is being used to transfer resistance to cherry leaf spot to cultivated tart cherry. Because this wild species has small fruit, a commercial cultivar will be obtained in fewer generations if interspecific hybrid seedlings (introgression lines) that are disease resistant but also possess large-fruit alleles can be used as parents. Large-fruit alleles are typically inherited sporadically from elite parents. Five genomic regions have been identified that contain genes that control fruit size (chromosomes 2, 3, 3 again, 5, and 6). Easy-to-use diagnostic markers are available for the trait loci of chromosomes 2 and 6 and will be used on seedlings in late 2013 in time for 2014 crossing.

Deliverable #13: Tool – a DNA test for cherry leaf spot resistance for parent selection use

To Whom: Amy Iezzoni, tart cherry breeder, Michigan State University

Story: Cherry leaf spot is the most important disease affecting tart cherry in the major U.S. production regions with multiple fungicide applications required to maintain healthy leaves on the trees. Leaf spot resistance is being bred into tart cherry from the wild species, Prunus canescens. An SSR-based DNA test targeting a chromosome 4 region was developed that can predict whether a cherry seedling will be resistant to cherry leaf spot. Those seedlings with the resistance-associated SSR allele can be used as parents to transfer the resistance more quickly to the next generation. All resistant tart cherry individuals must carry this P. canescens-derived SSR allele; however, a second as-yet unidentified locus is also needed to confer resistance.

To Whom: Amy Iezzoni, tart cherry breeder, Michigan State University

Story: Tart cherry selections can either be self-compatible (SC) or self-incompatible (SI). Any commercially acceptable cultivar must be SC, therefore not requiring the planting of a pollinator variety. DNA tests are available to determine whether a tart cherry individual is SI or SC. This information is being used to distinguish SI and SC seedlings prior to field planting. Also, due to the large number of alleles at the locus controlling this trait, these DNA tests are also being used to determine if progeny individuals are derived from the intended cross thereby eliminating progeny individuals derived from unintended self- or open-pollinations.

Deliverable #15: Tool – a high-throughput DNA test for large fruit size

To Whom: Nnadozie Oraguzie, stone fruit breeder, Washington State University

Story: Two SSRs flanking a QTL for fruit size on chromosome 2 have been used as a routine DNA test in the Pacific Northwest Sweet Cherry Breeding Program (PNWSCBP) since 2010. Amy Iezzoni, Jim Olmstead, and colleagues first identified these diagnostic markers in a mapping population. The marker-locus-trait association was subsequently validated in the PNWSCBP’s germplasm by Cameron Peace and Nnadozie Oraguzie in 2009. The test has proven useful for both MAPS and MASS, directing crosses towards large-fruited seedlings as well as saving an estimated >$100K to date by culling inferior seedlings. Usually, the Peace lab converts originally reported markers into new and improved ones that can be easily used in high-throughput seedling screening. However, both SSRs, CPSCT038 and BPPCT034, were immediately amenable to streamlined genotyping. In fact, when they were transferred from their original agarose gel separations to polyacrylamide gels (and later to ABI) further important allelic distinctions were made, with positive repercussions for associating trait levels. Recently, Amy Iezzoni and colleagues have reported the likely gene underlying this QTL. Will this mean the markers of this DNA test will be updated to lie right on the gene itself and thus be 100% predictive? Not necessarily. First, by flanking the locus, even ~20 cM apart, the two-SSR DNA test is almost 100% predictive. Second, the multitude of haplotypes that the two SSRs can distinguish appear to nicely separate out gradations in fruit size (and other traits with QTLs in this region), and any gene-based marker will have to reproduce that level of predictiveness if it wants to replace trusty “C’038 & B’034”!

To Whom: Nnadozie Oraguzie, stone fruit breeder, Washington State University

Story: The large number of alleles of BPPCT034, one of the SSRs for the DNA test for fruit size on cherry chromosome 2 (Deliverable #15), has proven useful for a second trait, firmness. The most common large-fruited allele is ‘255’, usually also associated with soft fruit. But then there is ‘237’, a large-fruited allele that is also associated with firm fruit. Cultivars carrying the rare ‘237’ – useful breeding parents – include ‘Kiona’, ‘Glacier’, and ‘Tieton’, which inherited this gem from their parent/grandparent, ‘Early Burlat’. The combination of ‘237’ and ‘255’ therefore makes for large and firm-fruited individuals, and crosses can target this combination to enrich progenies with the genetics for superior performance. This crossing strategy will be particularly useful for developing new early ripening cultivars that are large and firm, given that the majority of available early ripening cultivars produce either large and soft fruit or small and soft fruit.

Deliverable #17: Tool – a high-throughput DNA test for self-fertility

To Whom: Nnadozie Oraguzie, stone fruit breeder, Washington State University

Story: Self-compatibility (also known as self-fertility) is a valuable trait in sweet cherry, just as it is in tart cherry. However, the genetics are simpler in sweet cherry. The traditional approach to detecting self-fertility involves crossing experiments followed by microscopic analysis of pollen tube growth in the style. This approach is time consuming, requires trees to be flowering, and outcomes can be influenced by environmental conditions. A simple PCR test was developed for S4' allele detection. This allele confers self-fertility to any prospective parent, seedling, selection or new cultivar release carrying it. In 2009, PCR products separated on polyacrylamide gels. More recently, we upgraded the DNA test, adapting it to high-throughput running on an ABI DNA Analyzer. Now, thousands of seedlings can be screened in a day. This DNA test can also be multiplexed in PCR with the long-available “universal” S-genotyping primers to provide a versatile tool for elucidating most of the common S-genotypes in cultivated sweet cherry germplasm and identifying the self-fertile types among them.

To Whom: Nnadozie Oraguzie, stone fruit breeder, Washington State University

Story: Available advanced selections that had previously been elevated on phenotype alone were DNA-tested for fruit size and self-fertility. The results were factored into decisions about whether to advance the selections further, and several selections were dropped before further resources were expended on them. These DNA tests are now conducted routinely such that DNA information is considered earlier in selection advancement decisions.

To Whom: Nnadozie Oraguzie, stone fruit breeder, Washington State University

Story: ‘Kiona’ is an early-ripening sweet cherry cultivar, recently released from WSU’s breeding program, which blooms mid to late season in the Pacific Northwest and so it often escapes early spring frost damage. ‘Kiona’ was initially believed to be self-incompatible, requiring one or multiple pollenizer cultivars present at 10% in an orchard to maximize fruit production. S-genotyping subsequently determined that this cultivar is self-fertile (S4'S9) and therefore does not require bees or pollenizer trees for pollination – a boost to its adoption by growers.

Deliverable #20: Knowledge – incorrect parentage sorted out for an advanced selection

To Whom: Nnadozie Oraguzie, stone fruit breeder, Washington State University

Story: WSU-PC74 [coded] is a self-fertile late-season advanced selection originally thought to have arisen from a cross between two late-season cultivars, ‘Sweetheart’ and ‘Regina’. This selection has fruit with a good balance of sweetness and tartness and can easily pass for a descendant of Regina due to its rich flavor. Additionally, its fruit size genotype from the two SSR loci for fruit size on G2 (Deliverable #15) shows an inheritance pattern akin to progeny from both ‘Sweetheart’ and ‘Regina’. However, examination of its S-locus genotype (S4'S9) revealed that it did not inherit any alleles from ‘Regina’ (S1S3) but it does have the S4' allele from ‘Sweetheart’ (S3S4') that imparts valuable self-fertility. Proof was therefore obtained that ‘Sweetheart’ is the seed parent while the pollen parent remains unknown, and that the selection is self-fertile.

To Whom: Nnadozie Oraguzie, stone fruit breeder, Washington State University

Story: Several DNA tests used in the Washington Tree Fruit Genotyping Lab in Pullman, WA for high-throughput screening of sweet cherry seedlings of WSU’s Pacific Northwest sweet cherry breeding program have provided valuable information about crossing method effectiveness in this breeding program. During the flowering season, parent trees can be emasculated, hand-pollinated, and then either bagged or left exposed to the elements and bees. Bagging branches of hand-pollinated flowers should increase the proportion of seedlings with intended fathers, but is the extra effort worthwhile? Also, bagging flowers of self-fertile cultivars is a way to ensure selfing when desired to enrich a progeny with favorable alleles carried by a particular parent. Not conducting controlled pollination but rather letting bees do the work then collecting fruit (seed) from superior mothers is another potentially useful approach, especially to boost seed number, as long as the bee-spread pollen pool contains a high proportion of valuable alleles. Genotyping of large breeding populations resulting from both controlled and open pollination, using DNA tests primarily used to target the S locus and fruit size trait loci, has revealed that (1) controlled crossing without bagging provides ~70% intended parentage, (2) open-pollinated progenies carry a high proportion of desirable genotypes for the main fruit size locus, and (3) selfing is a common outcome when self-fertile parents are open-pollinated. This information is used to adjust the level of effort and control put into crossing each spring. The information has also been used to confirm that exotic sweet cherry pollen imported from Europe and used in this program for the last decade has successfully fathered thousands of breeding seedlings, infusing valuable alleles.

To Whom: Nnadozie Oraguzie, stone fruit breeder, Washington State University

Story: Targeted crosses are now made in Dr. Oraguzie’s sweet cherry breeding program that take into account knowledge of S-genotypes and functional haplotypes for fruit size. The resulting seedlings are subjected to DNA tests while in the greenhouse to eliminate seedlings with inferior genotypes (not self-fertile and small fruited) while carrying through to the field only individuals that have favorable DNA profiles. Since 2010, more than 3000 seedlings have been eliminated, more than half of those tested. The survivors, now growing in the breeding orchard, are therefore expected to be self-fertile and enriched for genetic potential for large fruit size.

To Whom: Nnadozie Oraguzie, stone fruit breeder, Washington State University

Story: ‘Cristobalina’ is a Spanish landrace of sweet cherry imported by Amy Iezzoni as pollen to introgress a novel source of self-fertility in WSU’s sweet cherry breeding program. This cultivar is also early-season ripening, another valuable trait. Recent research at the CITA research institution in Zaragoza, Spain, confirmed that ‘Cristobalina’s self-fertility is due to a different locus (on chromosome 3) than the S locus source of the S4' allele (chromosome 6), the only source of self-fertility widely exploited in the last half-century of sweet cherry breeding. Introgressing this novel source is expected to help minimize inbreeding. The early ripening is a bonus! However, none of the first-generation ‘Cristobalina’ progeny are expected to have commercial value. Quickly identifying those seedlings carrying this self-fertility as well as large fruit size alleles and with the early ripening phenotype would be very useful so that just those seedlings could be used as parents for the next generation. The markers published in the CITA research were adapted to our local (Pullman, WA) DNA testing facilities in early 2013 and used to narrow down a pool of 300 seedlings to just two that carry all target attributes.

Deliverable #24: Germplasm – access to new genepools and potential cultivar-generating progenies with novel sources of self-fertility and early season ripening

To Whom: Nnadozie Oraguzie, stone fruit breeder, Washington State University

Story: Two newly flowering seedlings of ‘Cristobalina’ were used as parents in spring 2013. These seedlings were determined to carry the right alleles for a new source of self-fertility and large-size fruit by DNA tests and probably also carry alleles for early season ripening judging by their extreme phenotype. By making crosses with these two individuals, the valuable alleles were imparted to the next generation, synergistically combining with alleles for other traits from other parents. This next generation, grandchildren of the Spanish landrace ‘Cristobalina’, may result in exciting new cultivars to support the sweet cherry industry of Washington. The timely use of DNA information to identify the most suitable introgression lines to feed into crossing decisions is a model approach for introgression of valuable traits from many other exotic germplasm sources used in WSU’s sweet cherry breeding program.

Deliverable #25: Knowledge – evolution of the Arkansas peach and nectarine breeding program

To Whom: John R. Clark, peach, grape, and small fruit breeder, University of Arkansas

Story: The University of Arkansas peach breeding program began in the 1960s and since then several peach and nectarine cultivars have been developed. The first peaches released were clingstone, non-melting with yellow flesh color destined for baby food. In recent years the objectives of the program have changed to focus on fresh-market cultivar development. To date, the program has released nine peach cultivars, five nectarine cultivars, advanced more than eight-hundred selections, and generated more than 100,000 seedlings using controlled crossing. Individuals are evaluated in the field by scoring of various traits. This evaluation method has been a successful and simple way to characterize the germplasm. Recently, the program has incorporated new techniques to more accurately evaluate commercially important traits such as sugar content, acidity, flesh firmness, flesh color, and skin color. These techniques along with the implementation of DNA-based tools are increasing the efficiency and efficacy of breeding decisions within the program.

Deliverable #26: Knowledge – more flesh textures within the program than expected

To Whom: John R. Clark, peach, grape, and small fruit breeder, University of Arkansas

Story: Melting and non-melting are the two most common peach flesh textures in the market and supposedly were the only two flesh types in the program. However, upon phenotypic characterization, some breeding lines presented textures that were distinct from the traditional types. These unusual flesh types often have a crispy texture, maintain their firmness longer, and show less internal damage throughout postharvest storage. In 2010, endoPG markers which differentiate peach flesh types were screened on Arkansas breeding germplasm. A novel flesh texture termed “non-softening” was confirmed to be present in the program by Breeding Trainee Paul Sandefur. The endoPG markers could not differentiate a second novel texture present in the program termed “slow-melting”. However, phenotypic analysis has shown that individuals with this flesh type maintain their firmness for a longer period and then eventually melt similar to standard melting. This phenotypic differentiation has fostered new research projects to determine the genetics of this novel flesh type. Studies of postharvest potential of these two novel flesh types are confirming their superior postharvest storage potential (Deliverable #27). These two novel flesh types could be valuable for the peach industry if incorporated into new fresh market peach cultivars to allow peaches to be picked at a later optimal maturity and still maintain firmness throughout storage for domestic and long-distance shipping.

Deliverable #27: Tool – protocol for peach postharvest cold-storage evaluation

To Whom: John R. Clark, peach, grape, and small fruit breeder, University of Arkansas

Story: During 2010-2012, a peach postharvest cold-storage evaluation protocol was developed and incorporated for standardized assessment of postharvest performance of Arkansas peach and nectarine seedlings and selections. According to this protocol, all fruit should be harvested at commercial ripeness and stored at ~0-1^◦C, 90-95% humidity, for four weeks. During this time, changes in soluble solid content, pH, titratable acidity, skin and flesh characteristics, flavor, firmness, mealiness, juiciness, and browning are measured to distinguish each individual’s optimal postharvest potential. Initial results include differences in storability among the non-melting, slow-melting, non-softening, and melting-flesh types for skin attributes, firmness, and juiciness. Interactions among genotypes, storage lengths, textures, and fruit types were found. These results could be critical in revealing the postharvest potential of specific textures types in the Arkansas peach breeding program. Ultimately, the hope is to incorporate these beneficial flesh traits into peaches currently in the commercial market and thus increase the postharvest life of commercially produced peach cultivars.

Deliverable #28: Knowledge – diversification of flavors within the University of Arkansas peach breeding program

To Whom: John R. Clark, peach, grape, and small fruit breeder, University of Arkansas

Story: During the last decade the aim of the Arkansas program has been to increase the diversity of flavors and create peaches and nectarines pleasant to eat to satisfy a wide array of consumer palates. Acidity, measured as titratable acidity, is a flavor component which has a big impact on the acceptance or rejection of a cultivar by consumers. Phenotyping of this trait was performed on Arkansas breeding germplasm during the 2010, 2011, and 2012 seasons. Immense variation and transgressive segregants for both high and low acidity were observed. Additionally, a DNA marker associated with acidity, near the D locus, was used. One marker allele was confirmed to be associated with high acidity and another with low acidity. The low acidity allele appears to be dominant. This knowledge will be used to assist in designing crosses and screening seedlings before planting in the field to target diversified acidity levels in program.

Deliverable #29: Germplasm – prevalence of bacterial spot resistance confirmed in the University of Arkansas peach breeding program

To Whom: John R. Clark, peach, grape, and small fruit breeder, University of Arkansas.

Story: Bacterial spot resistance has been a key trait of interest throughout the existence of the peach breeding program at the University of Arkansas. The warm and humid spring and summers in Arkansas provides an ideal environment for widespread occurrence of this disease. This environment has enabled breeding and selection of peaches with low bacterial spot incidence. Recently, alleles associated with bacterial spot resistance vs. susceptibility have been uncovered. Presence/absence of these alleles was determined across the program’s germplasm. The resistance alleles are more common in Arkansas material than susceptibility alleles. This finding is very promising and further verifies resistance to bacterial spot in the Arkansas peach material.

Deliverable #30: Tool – incorporation of molecular techniques and a molecular lab established

To Whom: John R. Clark, peach, grape, and small fruit breeder, University of Arkansas

Story: Up until the advent of RosBREED, the University of Arkansas peach breeding program practiced only conventional breeding techniques: phenotypically based parent selection, crossing, and seedling selection. In 2010, the program became a part of RosBREED, which brought forth the first ideas to incorporate molecular tools to assist conventional selection operations. During the project, four cultivars, 16 selections, and 136 seedlings from the Arkansas program were genotyped with the IPSC peach 9K SNP array v1. All individuals were phenotyped, using protocols standardized with other U.S. peach breeding programs, for three years. This genotypic and phenotypic data is being extensively mined for discovery of loci controlling important peach fruit quality traits. In January 2013, the program set up its own molecular lab for local DNA testing support. All the basic equipment and reagents for a fully functioning molecular laboratory were purchased and set up. RosBREED was essential for the incorporation of molecular techniques into this conventional program. Through RosBREED, with trait locus discovery and DNA test validation, new peach cultivars will be developed with increased effectiveness and efficiency.

Deliverable #31: Knowledge – validation and incorporation of MAB into the program in 2013/2014

To Whom: John R. Clark, peach, grape, and small fruit breeder, University of Arkansas

Story: Leaf samples have been collected from the program’s 15 cultivars, 103 advanced selections, and 50 interesting new selections from among 78 field-planted populations. These individuals have been phenotyped for several years for important peach industry traits: flesh texture, size, flavor, skin color, bacterial spot resistance, bloom date, and maturity date. In summer 2013, detailed phenotyping will commence on these individuals. In fall 2013, available DNA tests for flesh texture, fruit size, flavor, skin color, bacterial spot resistance, bloom date, and maturity date will be screened on all collected material to confirm marker associations with their respective traits. The ultimate goal is the implementation of MAB for future generations. In the winter of 2013/2014, parents will be chosen based on their phenotypic and genotypic potential to pass on important traits. Once validated in the program, the markers will become useful tools for routine parent and seedling selection. Parents that are shown to have a high probability of contributing key commercial traits will be selected for crossing. Additionally, seedlings will be screened after germination for their genetic potential for the various traits and individuals lacking desired characteristics will be discarded prior to field planting – thus increasing breeding program efficiency.

Deliverable #32: Tool – a DNA test for red stele resistance

To Whom: Chad Finn, strawberry and other small fruit breeder, USDA-ARS-HCRL, Corvallis and James Hancock, strawberry and blueberry breeder, Michigan State University

Story: Red stele is an important root rot disease affecting strawberry in U.S. production regions, where a combination of cultural and chemical control and use of disease-free planting stocks are required to maintain healthy plants. Strawberry cultivars have been bred for red stele resistance since the 1930s and resistance to one or a few races of the pathogen was established by controlled screening, a time-consuming process requiring maintenance of isolates of well-defined differential races of this pathogen. It is currently limited to a single program in North America, that of Andrew Jamieson in Agriculture and Agri-Food Canada, in Nova Scotia, Canada. Cultivars that are resistant to one or a few of the pathogen races can be suitable for some growing regions but are not resistant to the disease overall. However, as not all races occur in the same regions, resistance can be bred for certain target regions. An SSR-based DNA test targeting one of the resistance loci, Rpf1, was proven to predict whether a strawberry seedling will be resistant to a specific set of races of the pathogen. Those seedlings with the resistance-associated SSR allele can be used as parents to transfer the resistance more quickly to the next generation and can be crossed with cultivars that are resistant to other races to develop new cultivars with multiple sources of resistance to this disease.

To Whom: Lise Mahoney, strawberry breeder, University of New Hampshire

Story: The training provided by RosBREED in the use of the software tool Pedimap facilitated an initiative to identify sources of resistance to verticillium wilt. Visualizing resistance and susceptibility to this devastating disease over the complicated pedigree of strawberry germplasm with Pedimap indicated useful sources of resistance and suggested mechanisms of inheritance.