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The genetic control of flowering habit in many species of Fragaria has not been well studied. Identification of flowering traits and patterns for these taxa could be used in the quest for perpetual flowering (PF) genes and for the octoploids, broaden the genepool of available PF parents for breeding programs. As such, clones from the Fragaria germplasm collection housed at the USDA-ARS National Clonal Germplasm Repository in Corvallis, OR, were evaluated to describe flowering habits in various taxa and identify PF clones. Flower presence was recorded monthly for 962 clones of 36 taxa from the first of May through October in 2015 and 2016 to determine flowering habit and pairwise comparisons between taxa were examined using Pearson’s Chi-squared test. Taxa with the largest percent of PF accessions were F. vesca subsp. vesca f. semperflorens, F. vesca subsp. vesca f. alba, F. vesca subsp. americana, and F. virginiana subsp. glauca. These taxa had similar flowering habits to each other but were significantly different (α = 0.05) from most other taxa in which the seasonal flowering (SF) trait was predominant. Fifteen clones that demonstrated the PF phenotype in both 2015 and 2016 were identified. Differing genetic controls have been observed for flowering habit in F. ×ananassa and F. vesca. Additional studies are needed to determine genetic control of flowering in other Fragaria taxa.
Confirming parentage and clonal identity is an important aspect of breeding and managing germplasm collections of clonally propagated, outcrossing crops, like blackberry (Rubus subgenus Rubus). DNA fingerprinting sets are used to identify off-cross progeny and confirm clonal identity. Previously, a six-simple sequence repeat (6-SSR) fingerprinting set was developed for blackberry using a small number of samples. The usefulness of the 6-SSR fingerprinting set for pedigree confirmation had not been evaluated. Therefore, it was used in this study to validate parentage for 6 and 12 biparental populations from the University of Arkansas (UA) and US Department of Agriculture Agricultural Research Service (USDA-ARS), Horticultural Crops Research Unit (HCRU) breeding programs, respectively. Twenty-seven of the 489 individuals in these breeding populations were identified as off-cross. The 6-SSR fingerprinting set was sufficient for parentage confirmation; however, a total of 61 plants distributed across 28 sets of genotypes could not be distinguished from each other. An 8-SSR fingerprinting set with improved resolution was subsequently developed and used to evaluate 177 Rubus accessions from the USDA-ARS National Clonal Germplasm Repository, UA, and USDA-ARS HCRU programs. The 8-SSR fingerprinting set distinguished all samples expected to have unique genotypes and identified differing DNA fingerprints for two sets of accessions suspected to have identical fingerprints. Cluster analysis grouped the accessions from the eastern and western US breeding programs based on geography and descent. Future work will focus on establishing a database of DNA fingerprints for germplasm identification and for determining pedigree relationships between blackberry accessions.
The availability of strawberry (Fragaria ×ananassa) genomic resources has increased dramatically in recent years. Some of these resources are readily applicable to strawberry breeding programs for use in DNA-informed breeding. Information about these tests and how to interpret them is dispersed through numerous manuscripts or in the laboratories that use them routinely. To assist breeders in identifying tests available to their breeding program and in implementing them in their program, a compendium of strawberry DNA tests was created. This compendium is available for download from the Genome Database for Rosaceae (https://www.rosaceae.org/organism/Fragaria/x-ananassa?pane=resource-4). This resource will be updated continually as old tests are modified and new tests are created.
The fungal pathogen, Diplocarpon rosae, infects only roses (Rosa spp.) and leads to rose black spot disease. Rose black spot is the most problematic disease of outdoor-grown roses worldwide due to the potential for rapid leaf chlorosis and defoliation. Eleven races of the pathogen were previously characterized from isolates collected in North America and Europe. Isolates of D. rosae obtained from infected leaves of the roses Brite EyesTM (‘RADbrite’; isolate BEP; collected in West Grove, PA) and Oso Easy® Paprika (‘CHEwmaytime’; isolate PAP; collected in Minneapolis, MN) proved to have unique infection patterns using the established host differential with the addition of Lemon FizzTM (‘KORlem’). The new races are designated race 12 (BEP) and race 13 (PAP), respectively, and Lemon FizzTM should be included in the updated host differential because it distinguishes races 7 and 12. Additionally, inconsistent infections and limited sporulation were found in the host differential Knock Out® (‘RADrazz’) for races 7 and 12. Expanding the collection of D. rosae races supports ongoing research efforts, including host resistance gene discovery and breeding new rose cultivars with increased and potentially durable resistance.