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- Author or Editor: Amy F. Iezzoni x
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.
Abstract
Michigan State Univ. (MSU) has a long history of rendering outstanding service to the citizens of Michigan, the nation, and the world. Founded in 1855 as the Agricultural College of the State of Michigan, the teaching institution soon began its tripartite mission of instruction, research, and public service. In 1862, the college became a prototype for the 68 land-grant colleges established under the Morrill Act. Now, 132 years later, MSU has 11 baccalaureate-granting colleges that offer more than 125 programs, many of these offering multiple fields of concentration, and an enrollment of ≈42,000 students.
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.
Abstract
Morphological traits of 16 sour cherry (Prunus cerasus L.) cultivars and of hybrid and open-pollinated seedlings of germplasm collected in eastern Europe were evaluated with principal component (PC) analysis. Due to the character loadings of the first three PCs in each analysis, some of the PCs can be interpreted as representing gradations between morphologies characteristic of the two presumed progenitor species, sweet cherry (P. avium L.) and ground cherry (P. fruticosa Pall.). Genetically related cultivars and families tend to cluster, indicating that there is a significant genetic component to the underlying patterns of morphological variation. Families of cold-hardy Russian cultivars generally show a greater morphological resemblance to ground cherry than do families of less cold-hardy cultivars, suggesting that selective forces may also have contributed to the patterns of morphological variation detected.
Microspore-derived callus cultures were obtained by anther culture of `Emperor Francis' sweet cherry (Prunus avium L.). Branches were removed from the field in January and March and forced in the laboratory. When the microspores reached the uninucleate stage, anthers were placed on modified Quoirin and Lepoivre liquid culture medium containing 4.4 μm BA and 4.5 μm 2,4-D. After ≈60 days, callus that emerged from the anthers was placed on woody plant medium supplemented with 1 μm 2,4-D and 3 μm 2iP and routinely transferred. The resulting 270 callus cultures were screened for two allozymes heterozygous in `Emperor Francis', Pgi-2 and 6-Pgd-1. Of the 270 callus cultures, 154 expressed only one allele each for Pgi-2 and 6-Pgd-1; thus, they were considered microspore-derived. The microspore-derived callus cultures can be used as a linkage mapping population. Chemical names used: 6-benzyladenine (BA); 2,4-dichlorophenoxyacetic acid (2,4-D); N6-(2-isopentenyl)-adenine (2iP).