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R.J. Schnell, J.S. Brown, C.T. Olano, E.J. Power, C.A. Krol, D.N. Kuhn, and J.C. Motamayor

Three horticultural races of avocado (Persea americana Mill.) are known: Guatemalan, Mexican, and West Indian. Each race has unique characteristics and current commercial varieties have been selected from within the races or from interracial hybrids. Using 14 microsatellite loci we investigated the genetic variation among 224 accessions (394 plants) maintained at the National Germplasm Repository (NGR) in Miami, Fla., and a set of 34 clones from the University of California South Coast Field Station (SCFS) located in Irvine, Calif. The 14 microsatellite loci had an average of 18.8 alleles per locus and average unbiased genetic diversity was 0.83. The total propagation error in the collection, i.e., plants that had been incorrectly labeled or grafted, was estimated to be 7.0%. Although many unique alleles did exist, no useful race-specific markers were found. A general concordance between the horticultural race and the clusters obtained from molecular data was observed. Principal Coordinate Analysis (PCA) grouped the Guatemalan and Mexican races into two distinct clusters. The West Indian also grouped into a unique major cluster but with an outlying group. Using the PCA a change in the racial designation or interracial hybrid status for 50 accessions (19.7%) is proposed. The unbiased gene diversity estimate was highest in the Mexican and Guatemalan races and lower in the West Indian group. This demonstrates the need to collect more of the West Indian germplasm to broaden the genetic diversity and to emphasize the identification of individuals conferring resistance to Phytophthora Root Rot (PRR).

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Eder J. Oliveira, Maria Lucia C. Vieira, Antonio Augusto F. Garcia, Carla F. Munhoz, Gabriel R.A. Margarido, Luciano Consoli, Frederico P. Matta, Michel C. Moraes, Maria I. Zucchi, and Maria Helena P. Fungaro

codominant markers, particularly microsatellite loci. To our knowledge, this is the first integrated genetic map of a passion fruit species. Materials and Methods Plant materials, extraction, and quantification of DNA. Carneiro et al. (2002

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Maria G. Emmanouilidou, Marios C. Kyriacou, and Isabel Trujillo

protocols for varietal identification. In this regard, a protocol recently has been established based on the integrated use of morphological and molecular markers (microsatellites) to facilitate the identification of the varieties present in olive gene banks

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Esther Giraldo, Margarita Lopez-Corrales, and Jose Ignacio Hormaza

, microsatellites or SSR (SSRs) have become the markers of choice for fingerprinting and analysis of genetic diversity in most plant species ( Gupta and Varshney, 2000 ) due to their high level of polymorphism, codominant Mendelian inheritance, reproducibility, and

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LJ Grauke, Maria Azucena Mendoza-Herrera, Carol Loopstra, and Tommy E. Thompson

Microsatellite or Simple Sequence Repeat (SSR) markers are being developed in ongoing research in the USDA ARS Pecan Breeding Program. These co-dominant markers provide a powerful tool for the verification of parentage. To confirm their utility, SSR profiles were used to confirm the parentage of 19 of the 25 controlled crosses released by the breeding program. Questions were raised concerning the parentage of some crosses thought to be known. When the genotype of the maternal parent is known, the paternal genotype necessary to have produced the progeny can be determined. A SAS program was written to query a database that includes 288 pecan accessions to find appropriate paternal genotypes given a maternal pattern. If neither parent is known, all possible parental combinations can be derived based on the progeny. Putative parents can be qualified on the basis of genotype as well as other evidence, such as nut morphology, dates of origin, locations of origin, and dichogamy. Using these techniques, putative parents are suggested for the historic cultivars `Riverside' and `Western'. Although the probabilities for a particular genotypic pattern can be determined based on allele frequencies within the population, assigning numeric probabilities to other evidence is more challenging. Meticulous records are necessary to establish the linkage between an inventory of an accession and its historic origin, thereby placing putative parents in combination at the proper place and appropriate time. Records of USDA–ARS National Plant Germplasm System, as exemplified by logbooks and vouchers of the McKay Collection of the National Arboretum, provide evidence for confident molecular genetic verification of cultivar identity and parentage, increasing the value of the living accessions in the NPGS.

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Yu Zong, Ping Sun, Xiaoyan Yue, Qingfeng Niu, and Yuanwen Teng

needed. In this study, we analyzed the geographical distribution of polymorphisms in nuclear microsatellite loci from the 18 P . betulaefolia populations that were reported in our previous study ( Zong et al., 2014 ). The main purpose of this study was

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Riaz Ahmad, Darush Struss, and Stephen M. Southwick

We evaluated the potential of microsatellite markers for use in Citrus genome analysis. Microsatellite loci were identified by screening enriched and nonenriched libraries developed from `Washington Navel' Citrus. Microsatellite-containing clones were sequenced and 26 specific PCR primers were selected for cross-species amplification and identification of cultivars/clones in Citrus. After an enrichment procedure, on average 69.9% of clones contained dinucleotide repeats (CA)n and (CT)n, in contrast to <25% of the clones that were identified as positive in hybridization screening of a nonenriched library. A library enriched for trinucleotide (CTT)n contained <15% of the clones with (CTT)n repeats. Repeat length for most of the dinucleotide microsatellites was in the range of 10 to 30 units. We observed that enrichment procedure pulled out more of the (CA)n repeats than (CT)n repeats from the Citrus genome. All microsatellites were polymorphic except one. No correlation was observed between the number of alleles and the number of microsatellite repeats. In total, 118 putative alleles were detected using 26 primer pairs. The number of putative alleles per primer pair ranged from one to nine with an average of 4.5. Microsatellite markers discriminated sweet oranges [Citrus sinensis (L.) osb], mandarin (Citrus reticulata Blanco), grapefruit (Citrus paradisi Macf.), lemon [Citrus limon (L.) Burm.f.], and citrange (hybrids of trifoliate orange and sweet orange), at the species level, but individual cultivars/clones within sweet oranges, mandarins and grapefruit known to have evolved by somatic mutation remained undistinguishable. Since these microsatellite markers were conserved within different Citrus species, they could be used for linkage mapping, evolutionary and taxonomic study in Citrus.

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Nahla V. Bassil, R. Botta, and S.A. Mehlenbacher

Three microsatellite-enriched libraries of the european hazelnut (Corylus avellana L.) were constructed: library A for CA repeats, library B for GA repeats, and library C for GAA repeats. Twenty-five primer pairs amplified easy-to-score single loci and were used to investigate polymorphism among 20 C. avellana genotypes and to evaluate cross-species amplification in seven Corylus L. species. Microsatellite alleles were estimated by fluorescent capillary electrophoresis fragment sizing. The number of alleles per locus ranged from 2 to 12 (average = 7.16) in C. avellana and from 5 to 22 overall (average = 13.32). With the exception of CAC-B110, di-nucleotide SSRs were characterized by a relatively large number of alleles per locus (≥5), high average observed and expected heterozygosity (Ho and He > 0.6), and a high mean polymorphic information content (PIC ≥ 0.6) in C. avellana. In contrast, tri-nucleotide microsatellites were more homozygous (Ho = 0.4 on average) and less informative than di-nucleotide simple sequence repeats (SSRs) as indicated by a lower mean number of alleles per locus (4.5), He (0.59), and PIC (0.54). Cross-species amplification in Corylus was demonstrated. These microsatellite markers were highly heterozygous and polymorphic and differentiated among genotypes of C. avellana irrespective of geographical origin. They will aid in fingerprinting genotypes of the european hazelnut and other Corylus species, genome mapping, and genetic diversity assessments.

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A. Belaj, G. Cipriani, R. Testolin, L. Rallo, and I. Trujillo

Nine simple-sequence-repeat (SSR) primer pairs were assayed in 35 Spanish and Italian olive cultivars of commercial interest. All microsatellites were polymorphic, showing 5 to 13 alleles per locus (7.5 alleles per locus on average). The frequency of each alleles was generally low, with most of the alleles present at one or two cultivars. Heterozigosity ranged from 0.15 to 0.95; the discrimination power (PD) ranged from 0.30 to 0.93 (mean 0.79). The set of microsatellites analyzed discriminated all cultivars investigated. The combination of only three SSR primer pairs—UDO99-009+UDO99-043+UDO99-14—made possible the identification of all cultivars included in the study. Cluster analysis did not find differences between Spanish and Italian cultivars, but most of the cultivars from southern and central Spain grouped together. Hence, microsatellites markers are recommended for olive fingerprinting to generate a database for olive cultivar identification.

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Zhi-Hong Gao, Zhi-Jun Shen, Zhen-Hai Han, Jing-Gui Fang, Yu-Ming Zhang, and Zhen Zhang

Sequencing amplification fragments produced using simple-sequence repeat (SSR) primer pairs pchgms2 and UDP96008 in `Dayezhugan' japanese apricot showed that SSRs obtained included a microsatellite locus originally identified in peach. The microsatellite sequence homogeneity between UDP96008 in japanese apricot in this study and UDP96008 in the peach in GenBank was 98%. Twenty-four japanese apricot genotypes originating in diverse geographic areas had been identified with 14 SSR primer pairs developed in different species of Prunus. In total, 129 alleles were obtained and per primer pairs detected 2.5 alleles on the average. The results from cluster analysis showed that the genetic distance between `Nanhong' and `Zhonghong' was the closest, and cultivars from China and from Japan could not be separated completely.