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Progress in sour cherry breeding in the U.S. is severely hampered by the limited germplasm available. Importing Prunus germplasm into the U.S. as budwood from the center of diversity in Eastern Europe, is impractical because of the lengthy quarantine period required. Instead it is proposed that pollen collection and the use of a tester clone would be the most efficient way to import and use sour cherry germplasm. Sour cherry pollen can be imported and used directly without a quarantine period. When the pollen is used in crosses with an appropriate tester clone, the breeding value of the germplasm can be assessed relatively easily because both parents are known as opposed to one parent as is the case with open-pollinated seed. Once a germplasm source has been identified as having a desired breeding value, pollen can again be imported or requested from the Plant Introduction Station where presumably the clone is still in quarantine, and used in routine breeding crosses. For a clone to be a good tester, it must induce precocity in the progeny and behave in a recessive manner for traits of importance. Data is presented to illustrate the use of the sour cherry cultivar English Morello as a tester clone for sour cherry germplasm evaluation.
Starch gel electrophoresis was employed to study inheritance and diversity of allozyme loci in a sour cherry (2n=4×=32) germplasm collection. Segregation data was collected for alcohol dehydrogenase (ADH), glucose phosphate isomerase (GPI), isocitrate dehydrogenase (IDH), leucine amino peptidase (LAP), malate dehydrogenase (MDH), peroxidase (PX) (cathodal activity), phosphoglucomutase (PGM), 6-phosphogluconic dehydrogenase (6-PGD), and shikimate dehydrogenase (s k d h).
Data suggest that alleles can be assigned to many of the enzyme systems being studied: ADH, GPI, IDH, LAP, PGM, and 6-PGD. Most loci are diallelic and often exhibit the unbalanced heterozygous condition. MDH, PX, and 6-PGD are highly polymorphic. Progeny segregation data fit disomic inheritance models, indicating that sour cherry is an allotetraploid.
Self-incompatibility was investigated in sour cherry (Prunus cerasus L.) by examining pollen growth in the pistil by use of ultraviolet fluorescence microscopy following self- and cross-pollination. The sour cherry cultivars Tschernokorka and Crisana exhibit pollen tube inhibition in the style characteristic of gametophytic self-incompatibility. `Meteor' and `Montmorency' appear to be partially self-incompatible, with few self-pollen tubes reaching the ovary. Several hybrid seedlings from crosses between self-compatible cultivars were self-incompatible, suggesting that these self-compatible parental cultivars carry self-incompatibility alleles.
The sour cherry (Prunus cerasus L.) industry in the United States is a monoculture of a 400-year-old cultivar from France named `Montmorency'. To provide a solid germplasm base to breed alternatives to `Montmorency', cherry germplasm was systematically collected over a 15-year period from its ancestral home in Central and Eastern Europe and introduced to the U.S. The strategy of germplasm collection using pollen, seed and budwood importation of highly quarantined species is discussed. Germplasm resulting from this effort is highlighted as well as an example of commercial success. Finally, the “recycling” of this immense germplasm collection to search for dwarfing precocious rootstocks for sweet cherry is described.
Fruit set in sweet (Prunus avium L.) and sour cherry (P. cerasus L.) is frequently less than adequate for profitable production despite the availability of compatible pollen and abundant flowers. When fruit set consistently falls below acceptable levels, growers may attempt to increase fruit set by increasing the availability of compatible pollen. We describe the use of the self-incompatibility locus (S-locus) as a genetic marker to quantify the relative contributions of competing pollen sources in achieving fruit set in ‘Balaton™’ sour cherry. Pollen race experiments were conducted to determine if nonself-pollen provided in a pollen mixture was more competitive than self-pollen in achieving fruit set in ‘Balaton™’. We further investigated what pollen set the ‘Balaton™’ crop in two commercial ‘Balaton™’ orchards where multiple potential pollinators were planted in adjacent orchards. S-allele genotyping using DNA extracted from the seed was done to discriminate among the competing pollen sources. The results suggest that in certain environmental conditions, nonself-pollen may be more competitive in achieving fruit set in ‘Balaton™’ than self-pollen. These examples illustrate how seed genotyping can be used to further our understanding of the competitive abilities of different pollen sources in both controlled experiments and production orchards.
Bloom times were evaluated for seedlings from four full-sib and 14 open-pollinated families of sour cherry (Prunus cerasus L.). Time of anthesis for individual seedlings ranged over 17and 16-day periods in 1989 and 1990, respectively. In both years, most seedlings bloomed later than `Montmorency', the only commercially important sour cherry cultivar in the United States. `Pitic de Iasi', the parent of the latest-blooming family, is a natural interspecific hybrid between sour cherry and the cold-hardy Russian ground cherry (P. fruticosa Pall.). Hybridization between sour and ground cherry and intense selection pressure in the colder areas of the sour cherry habitat may have favored selection of the late-blooming character.
Yield components were measured from 115 sour cherry (Prunus cerasus L.) hybrid seedlings from 13 full-sib families to investigate the potential of breeding for increased yield. Those families with the highest number of fruit and reproductive buds had the highest yields. In general, increased fruit size was not able to compensate for low fruit count. Fruit set and flower count per bud were inversely related, suggesting compensation between these two components. Yield components from six selections chosen for differing fruiting habits were measured for an additional 2 years. In year 1, those selections with a majority of their fruit on l-year-old wood had higher yield efficiencies (yield per branch cross-sectional area) than those with fruit on spurs; however, but year 3, the higher-yielding selections were those that fruited primarily on spurs. The data are discussed relative to selecting for yield in a sour cherry breeding program.
Black cherry (Prunus serotina Ehrh.) is a common secondary forest species with a wide endemic distribution ranging from Nova Scotia south into Mexico, Ecuador, and Peru. Although planted in the United States for its valued lumber, black cherry is essentially a wild species with small fruit ≈6 to 10 mm in diameter. In contrast, in Mexico and Ecuador, domesticates of this species called Capulin, have much larger (2 to 2.5 cm in diameter) edible fruit. To date, no studies of the genetic diversity within North American black cherry or the ancestral origin of the Capulin types have been conducted. Simple sequence repeats (SSRs, also termed microsatellites) would be the marker of choice for such genetic diversity studies due to their hypervariability; however, generation of these sequence-based markers is expensive. Therefore, our objective was to determine if markers already identified in other Prunus L. species would be informative in black cherry. The black cherry germplasm screened consisted of selections originating from Michigan, Mexico, and Ecuador. A chloroplast DNA marker, originally generated from sour cherry (P. cerasus L.), amplified three different sized products in black cherry. Four of the eight nuclear SSR markers tested from peach [P. persica L. Batsch (Peach Group)], sour cherry, and sweet cherry (P. avium L.) also amplified and identified polymorphic markers. Together these four primer pairs resolved 54 putative alleles for the 66 black cherry accessions assayed. Success of the sweet cherry, peach, and sour cherry primers in identification of polymorphic markers in black cherry indicates it should be possible to use these markers for comprehensive molecular genetic studies in black cherry.
Sour cherry (Prunus cerasus) is an allotetraploid with sweet cherry (P. avium) and ground cherry (P. fruticosa) as the proposed progenitor species. Three cpDNA markers from eight sweet, four ground, and 26 sour cherry selections were analyzed to investigate the relatedness of their cp genomes. To date, two RFLP polymorphisms have been identified with both the P2 and P4 fragments of tomato cpDNA, while four length polymorphisms of an intergenic spacer have been identified by PCR amplification. Sweet and ground cherry have different cp polymorphisms, while sour cherry individuals have been identified that have the sweet and ground cherry polymorphisms plus a unique polymorphism. Additional individuals chosen to represent the diversity within each species will be screened to provide a more complete assessment of cp diversity. In addition, progeny from a sour cherry cross where the parents have different cp polymorphisms are being evaluated to determine if the chloroplasts are exclusively maternally inherited.