Methods
Curatorial revision of core accession selections
Study Name: Pear Evaluation Data 1986 Experiment Type: Field FIELD Study Year: 1986 Year started: 02/01/1986
Study Name: Pear Evaluation Data 1987 Experiment Type: Field FIELD Study Year: 1987 Year started: 02/01/1987
Study Name: Pear Evaluation Data 1988 Experiment Type: Field FIELD Study Year: 1988 Year started: 02/02/1988
Experiment Type: Field FIELD Study Year: 1989 Year started: 02/01/1989
Study Name: Pear Field Evaluation 1990 Experiment Type: Field FIELD Study Year: 1990 Year started: 02/01/1990 Year ended: 11/01/1990 Experiment length: 10 months
Study Name: Pyrus field observations 1991 Experiment Type: Field FIELD Study Year: 1991 Year started: 01/01/1991 Year ended: 12/31/1991 Experiment length: 1 year
Field observations for fruit scab symptoms at time of fruit ripening.
Field observations for fruit scab symptoms at time of fruit ripening.
Field observations for fruit scab symptoms at time of fruit ripening.
Field observations for fruit scab symptoms at time of fruit ripening.
Field observations for fruit scab symptoms at time of fruit ripening.
Field observations for fruit scab symptoms at time of fruit ripening.
Greenhouse inoculation, 3 potted replicate trees per accession. Hood River, Oregon, 2002.
Fabraea Leafspot field observations in NCGR gene bank orchard,Corvallis, Oregon. Observations made on single tree per accession, July, 2003.
Field observations for fruit scab symptoms at time of fruit ripening.
3 potted replicate trees per accession were placed beneath infected orchard trees in Hood River, Oregon in late spring. Natural infections were recorded in August, 2003.
Field observations for fruit scab symptoms at time of fruit ripening.
Study Name: Pyrus fruit evaluation data for years 1987-88 Experiment Type: Field
The European Cooperative Program for Plant Genetic Resources (ECPGR) developed a 12 dinucleotide SSR fingerprinting set to genotype and compare individuals within and between germplasm collections (Evans et al., 2015). The SSRs in the ECPGR fingerprinting set are amplified in two PCR reactions. They contain dinucleotide motifs and thus exhibit various artifacts such as stutters, split peaks, and binning errors, making the ECPGR fingerprinting set difficult to use (Evans et al., 2015). In this study, an easy-to-use, single reaction, 10-SSR fingerprint set containing mostly high-core repeat SSRs was developed and compared to the ECPGR set and to single nucleotide polymorphism (SNP) markers found on the new 70K pear Axiom™ array (Montanari et al., 2019) in 152 and 237 accessions, respectively, for its ability to assess diversity, population structure, pedigree, and identity. PCR reactions for each of the three multiplexes in the ECPGR set and for this new U.S. Pyrus Genetic Resources (USPGR) fingerprinting set were conducted in 15 μL volumes consisting of 8.3 μL of 2× Type-it Multiplex PCR Master Mix (Qiagen N.V.), 1.5 μL of PCR grade water, 1.7 μL of primer mix, and 3.5 μL of DNA at a concentration of 3 ng/μL. The primers were optimized to the following concentration in the primer mix TXY276-0.25µM; TsuENH046-0.25µM; TsuENH083-0.375µM; TsuENH089-0.12µM; TsuENH076-0.18µM; CH04e03-0.5µM; CH01d08-0.36µM; NAUpy40d-0.18µM; TsuENH080_354-0.375µM; TXY144_347-0.18µM. The ECPGR optimized primer concentrations were as follows for Mpx 1:EMPc117-1µM; CH05c06-1.5µM; GD147-2µM; EMPc11-0.5µM:Mpx 2: CH04e03-1µM; CH01f07a-0.38µM; CH03g07-1.5µM; CH01d08-2µM: and Mpx 3: CH03d12-2µM; CH02b10-0.5µM; CH01d09-0.63µM; GD96-2µM. Reactions for both fingerprinting sets were amplified in an Eppendorf Gradient thermocycler (Eppendorf Inc., Westbury, NY, U.S.A.) using a program consisting of an initial denaturation at 95 °C for 5 min; 10 cycles of denaturation at 95 °C for 30 s, annealing for 1.5 min starting at 62°C and decreasing by 1 °C per cycle, and extension at 72 °C for 30 s; 30 cycles of denaturation at 95 °C for 30 s, annealing at 52 °C for 1.5 min, and extension at 72 °C for 30 s; followed by a 30 min hold at 60 °C. PCR products were pooled for Mpx 1 and Mpx 2 of the ECPGR set and all PCR products were separated via capillary electrophoresis using a Beckman Coulter CEQ 8000 (Beckman Coulter Inc., Brea, CA, U.S.A.).
Ploidy level determined by nuclear DNA content using flow cytometry. Performed by the Plant Cytometry Service, Netherlands
Ploidy level determined by nuclear DNA content using flow cytometry. Performed by the Plant Cytometry Service, Netherlands
Ploidy level determined by nuclear DNA content using flow cytometry. Performed by the Plant Cytometry Service, Netherlands
Ploidy level determined by nuclear DNA content using flow cytometry. Performed by the Plant Cytometry Service, Netherlands
Ploidy level determined by nuclear DNA content using flow cytometry. Performed by the Plant Cytometry Service, Netherlands
Study Name: Pear chilling units Experiment Type: Field FIELD Study Year: 1991 Year started: //1990 Year ended: //1991
Study Name: Pyrus observation data Experiment Type: FIELD FIELD Study Year: 1992 Year started: //1992 Year ended: //1992
Fire blight, caused by the bacterial pathogen Erwinia amylovora, is a persistent problem for pear (Pyrus spp.) growers in the United States. Growing resistant cultivars is one of the best options for managing fire blight. The cultivars Potomac and Old Home and the selection NJA2R59T69 display resistance to fire blight. As such, three mapping populations (El Dorado × Potomac, Old Home × Bartlett, and NJA2R59T69 × Bartlett) were developed to identify genomic regions associated with resistance to fire blight. Progeny were phenotyped during 2017 and 2018 by inoculating multiple actively growing shoots of field-grown seedling trees with E. amylovora isolate E153n via the cut-leaf method. Genotyping was conducted using the recently developed Axiom Pear 70 K Genotyping Array and chromosomal linkage groups were created for each population. An integrated two-way pseudo-testcross approach was used to map quantitative trait loci (QTLs). Resistance QTLs were identified on chromosome 2 for each population. The QTLs identified in the El Dorado × Potomac and Old Home × Bartlett populations are in the same region as QTLs that were previously identified in Harrow Sweet and Moonglow. The QTL in NJA2R59T69 mapped proximally to the previously identified QTLs and originated from an unknown Asian or occidental source. Future research will focus on further characterizing the resistance regions and developing tools for DNA-informed breeding.