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  • Author or Editor: Amy F. Iezzoni x
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Understanding the genetic control of fruit size in sweet cherry (Prunus avium L.) is critical for maximizing fruit size and profitable fresh market production. In cherry, coordinated cycles of cell division and expansion of the carpel result in a fleshy mesocarp that adheres to a stony endocarp. How these structural changes are influenced by differing genetics and environments to result in differing fruit sizes is not known. Thus, the authors measured mesocarp cell length and cell number as components of fruit size. To determine the relative genotypic contribution, five sweet cherry cultivars ranging from ≈1 to 13 g fresh weight were evaluated. To determine the relative environmental contribution to fruit size, different-size fruit within the same genotype and from the same genotype grown in different environments were evaluated. Mesocarp cell number was the major contributor to the differences in fruit equatorial diameter among the five sweet cherry cultivars. The cultivars fell into three significantly different cell number classes: ≈28 cells, ≈45 cells, and ≈78 cells per radial mesocarp section. Furthermore, mesocarp cell number was remarkably stable and virtually unaffected by the environment as neither growing location nor physiological factors that reduced final fruit size significantly altered the cell numbers. Cell length was also significantly different among the cultivars, but failed to contribute to the overall difference in fruit size. Cell length was significantly influenced by the environment, indicating that cultural practices that maximize mesocarp cell size should be used to achieve a cultivar's fruit size potential.

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Correct assignment of self-incompatibility alleles (S-alleles) in sweet cherry (Prunus avium L.) is important to assure fruit set in field plantings and breeding crosses. Until recently, only six S-alleles had been assigned. With the determination that the stylar product of the S-locus is a ribonuclease (RNase) and subsequent cloning of the S-RNases, it has been possible to use isoenzyme and DNA analysis to genotype S-alleles. As a result, numerous additional S-alleles have been identified; however, since different groups used different strategies for genotype analysis and different cultivars, the nomenclature contained inconsistencies and redundancies. In this study restriction fragment-length polymorphism (RFLP) profiles are presented using HindIII, EcoRI, DraI, or XbaI restriction digests of the S-alleles present in 22 sweet cherry cultivars which were chosen based upon their unique S-allele designations and/or their importance to the United States sweet cherry breeding community. Twelve previously published alleles (S1, S2, S3, S4, S5, S6, S7, S9, S10, S11, S12, and S13 ) could be differentiated by their RFLP profiles for each of the four restriction enzymes. Two new putative S-alleles, both found in `NY1625', are reported, bringing the total to 14 differentiable alleles. We propose the adoption of a standard nomenclature in which the sweet cherry cultivars `Hedelfingen' and `Burlat' are S3S5 and S3S9 , respectively. Fragment sizes for each S-allele/restriction enzyme combination are presented for reference in future S-allele discovery projects.

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The mean inbreeding and coancestry coefficients were calculated for almond, Prunus dulcis (Miller) D.A. Webb, cultivars from the United States, France, Spain, Israel, and Russia. To improve cultivars to meet market demand, the recurrent use of four selections as parents in U.S. breeding programs has resulted in a mean inbreeding coefficient (F) of 0.022 in this collection. In France, a single cultivar, Ferralise, has an inbreeding value of F = 0.250, while cultivars of other almond-producing countries are noninbred (F = 0). Due to the use of common parents, U.S., Russian, and Israeli cultivars share coancestry, while coancestries also exist between French and Spanish almond germplasm. Cultivars of known parentage in the United States, Russia, Israel, France, and Spain trace back, respectively, to nine, eight, three, four, and three founding clones. Future almond-breeding programs may narrow the genetic base and thereby limit genetic gain.

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Orthologs of CBF1, a cold-induced transcription factor important in the cold acclimation response in Arabidopsis thaliana were cloned from strawberry (Fragaria × ananassa Duchesne) and sour cherry (Prunus cerasus L.) with degenerate PCR primers. The putative orthologs [Fragaria ×ananassa CBF1 (FaCBF1) and Prunus cerasus CBF1 (PcCBF1)] have 48% amino acid identity to CBF1 and mRNA levels were up-regulated in leaves of both crops following exposure to 4 °C from 15 minutes to 24 hours. However, mRNA of FaCBF1 and PcCBF1 was not detected in pistils of strawberry and sour cherry following 4 °C exposure. Agrobacterium-mediated transformation of a CaMV35S-CBF1 construct was conducted on Fragaria ×ananassa `Honeoye' crown discs. Two transgenic lines were regenerated that expressed the transgene at low levels in both leaves and receptacles. Receptacles of the transgenic lines showed no significant change in freezing tolerance when compared to wild type plants, although the temperature at which 50 % electrolyte leakage occurred in detached leaf discs from the two transgenic lines was -8.2 °C and -10.3 °C, respectively. These freezing tolerance values were significantly greater than the value for the wild-type `Honeoye' leaf discs of -6.4 °C.

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The U.S. Department of Agriculture (USDA), Agricultural Research Service (ARS) tetraploid cherry (Prunus L. sp.) collection at Geneva, N.Y., contains ≈75 accessions of sour cherry (P. cerasus L.), ground cherry (P. fruticosa Pall.), and their hybrids. Accurate and unambiguous identification of these accessions is essential for germplasm preservation and use. Simple sequence repeats (SSRs) are currently the markers of choice for germplasm fingerprinting because they characteristically display high levels of polymorphism. Recently SSR primer pairs from sweet cherry (P. avium L.), sour cherry, and peach [(P. persica L. Batsch (Peach Group)] have been reported. Ten SSR primer pairs were tested on 59 tetraploid cherry accessions to determine if they could differentiate among the accessions. Scorable SSR fragments were produced with all primer-accession combinations. The cherry accessions exhibited high levels of polymorphism with 4 to 16 different putative alleles amplified per primer pair. Most of the putative alleles were rare with frequencies <0.05. Heterozygosity values ranged from 0.679 to 1.00, while gene diversity values ranged from 0.655 to 0.906. The primer pairs differentiated all but two of the 59 cherry accessions. Based upon the ability of the SSR data to differentiate the cherry accessions and the high level of gene diversity, we propose that all the tetraploid cherry accessions in the USDA/ARS collection be fingerprinted to provide a mechanism to verify the identity of the individual accessions. The fingerprinting data are available on the World Wide Web (http://www.ars-grin.gov/gen/cherry.html) so that other curators and scientists working with cherry can verify identities and novel types in their collections and contribute to a global database.

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This report demonstrates the presence of S-ribonucleases (S-RNases), which are associated with gametophytic self-incompatibility (SI) in Prunus L., in styles of self-incompatible and self-compatible (SC) selections of tetraploid sour cherry (Prunus cerasus L.). Based on self-pollen tube growth in the styles of 13 sour cherry selections, seven selections were SC, while six selections were SI. In the SI selections, the swelling of pollen tube tips, which is typical of SI pollen tube growth in gametophytic SI, was observed. Stylar extracts of these selections were evaluated by two-dimensional polyacrylamide gel electrophoresis. Glycoproteins which had molecular weights and isoelectric points similar to those of S-RNases in other Prunus sp. were detected in all selections tested. These proteins had immunological characteristics and N-terminal amino acid sequences consistent with the S-RNases in other Prunus sp. Two cDNAs encoding glycoproteins from `Erdi Botermo' were cloned. One of them had the same nucleotide sequence as that of S4 -RNase of sweet cherry (Prunus avium L.), while the amino acid sequence from the other cDNA encoded a novel S-RNase (named Sa -RNase in this study). This novel RNase contained two active sites of T2/S type RNases and five regions conserved among other Prunus S-RNases. Genomic DNA blot analysis using cDNAs encoding S-RNases of sweet cherry as probes indicated that three or four S-RNase alleles are present in the genome of each selection regardless of SI. All of the selections tested seemed to have at least one S-allele that is also found in sweet cherry. Genetic control of SI/SC in tetraploid sour cherry is discussed based on the results obtained from restriction fragment length polymorphism analysis.

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‘Bing’ is an iconic sweet cherry (Prunus avium L.) cultivar in the United States that even after more than 130 years of cultivation remains the most highly regarded dark sweet cherry and is the standard by which new sweet cherries are judged. ‘Bing’ has been repeatedly used as a parent in North American breeding programs and is found in the lineages of several important modern cultivars. The maternal parent of ‘Bing’ is reported to be ‘Black Republican’, an old cultivar commercially grown for fruit in the Willamette Valley, OR, after ≈1860 and now is usually only grown as a pollenizer cultivar; however, the paternal parent of ‘Bing’ is unknown. The objective of this study was to deduce the paternal parent of ‘Bing’ and validate the pedigree records for the relatives of ‘Bing’ using statistical algorithms that use genomewide single nucleotide polymorphism (SNP) data. With a high probability, it was determined that the sweet cherry cultivar Napoleon, also known as Royal Ann in the Pacific northwestern United States, a large, firm, blush-type, light-fleshed, and productive cherry, is the paternal parent of ‘Bing’. This parentage deduction results in an increase in the known relatedness among U.S. cultivated sweet cherry breeding germplasm because ‘Napoleon’ is an important founder previously known to be present in the ancestry of every self-compatible sweet cherry cultivar bred to date, directly and through ‘Bing’ and its descendants.

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Systematic studies of the relative importance of apple traits for U.S. apple producers to inform U.S. apple breeding programs have been lacking. To fill this gap, a series of audience surveys with instant feedback at five apple producer meetings across the United States was conducted. The traits included in this study were fruit crispness, juiciness, firmness, flavor, soluble solids concentration, sugar–acid balance, shelf life at retail, freedom from storage disorders, host plant disease resistance, and other fruit and tree traits provided by the producer. Producers rated fruit flavor and crispness as the most important traits for a successful apple cultivar. The relative importance assigned to traits was associated with growing location and producers’ years of experience in the decision-making process of managing apple orchards. This study contributes directly to a larger effort that provides breeding programs with systematic knowledge of trait preferences of supply chain members, including producers, and should result in a more targeted approach to developing and commercializing new apple cultivars.

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The primary goal of this research was to evaluate the relative importance of strawberry fruit quality and plant traits to strawberry producers. Previous studies focus on strawberry traits that impact postharvest quality and marketable yield; however, studies emphasizing the importance of these traits to strawberry producers are scarce. To investigate U.S. strawberry producer trait preferences, a series of audience surveys were conducted at four strawberry producer meetings across the United States. Results indicate that fruit firmness, fruit flavor, and fruit shelf life at retail were the most important fruit/plant traits to producers for a successful strawberry cultivar to possess. Growing state and producers’ years involved in the decision-making process of strawberry farms impacted the relative importance of the fruit/plant traits. This study directly contributes to a larger investigation of supply chain members’ trait preferences to improve the efficiency of Rosaceae fruit crop breeding programs and to increase the likelihood of new cultivar adoption. The overall project should result in a more efficient approach to new strawberry cultivar development and commercialization.

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