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A. Virginia Freire, John E. Preece, and David A. Lightfoot

Silver maple has great potential as a biomass feedstock. We compared three clones from each of seven provenances located on east to west and north to south transects across the natural range of silver maple and one red maple. DNA extracted by a modification of the CTAB technique (Murray and Thompson, 1980) was not suitable for RAPD analysis. Using this technique, polymorphism was either not reproducible or there was poor amplification for some clones. A new DNA extraction technique using PVPP, chloroform, and cesium chloride was tested (a modification of Yoon et al., 1991). this method yielded DNA that was more suitable for PCR amplification. Both RAPD and DAF (Caetano-Anolles and Gresshoff, 1994) methods were used for amplification. Polymorphism was detected among and within provenances. DAF was more efficient than RAPDs for determination of the genetic relationship among silver maple clones.

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John McCallum, Susan Thomson, Meeghan Pither-Joyce, Fernand Kenel, Andrew Clarke, and Michael J. Havey

limited studies of A. cepa diversity ( Dennequin et al., 1997 ; Tanikawa et al., 2002 ), but a more detailed evaluation by Bradeen and Havey (1995a) showed that identification of reliable, heritable polymorphisms is very challenging in onion. Isozyme

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Joseph N. Wolukau, Xiaohui Zhou, and JinFeng Chen

for resistance can also be used to pyramid resistance genes into commercially acceptable cultivars. Amplified fragment length polymorphism (AFLP) markers combined with bulk segregant analysis (BSA) is a powerful technique for identifying markers linked

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B.J. Weir, R.G. St. Pierre, and R.N. Chibbar

Randomly amplified polymorphic DNA (RAPD) markers were used to distinguish among 16 cultivars of saskatoon (Amelanchier spp.). Eight 9-base, oligonucleotide primers amplified a total of 98 DNA fragments, of which 29 were useful as reproducible polymorphic markers. Twelve cultivars and two pairs of cultivars were uniquely characterized by these 29 markers. Polymorphism was not detected among five sources of the cv. Thiessen, whereas variability was found among seedlings from self-pollinated `Thiessen'. Samples of the cvs. Regent and Parkhill were indistinguishable from one of two sources, suggesting that the cultivars were mislabelled.

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Sriyani Rajapakse, Albert Abbott, John Kelly, and Robert Ballard

The feasibility of using RFLP to distinguish genetically related Hybrid Tea rose cultivars for DNA `fingerprinting' was examined with a group of cultivars related to `Peace'. The following cultivars used in this study, `Chicago Peace', `Flaming Peace', `Climbing Peace' and `Lucky Piece', were derived from bud mutations (sports) of `Peace'. We also investigated two additional cultivars, `Perfume Delight' and `Garden Party', in which one of the parents for each was `Peace'. Genomic rose DNA probes, cloned in pUC8 plasmid of Escherichia coli, were hybridized with genomic DNA of these cultivars digested with different restriction enzymes. Although polymorphisms were observed among these related cultivars, only a few probe/enzyme combinations screened produced RFLPs due to the high degree of genetic relatedness of these cultivars. We have identified probes that can distinguish all of these related rose cultivars. This study demonstrates that RFLP markers can be used effectively in DNA `fingerprinting' of genetically related rose cultivars, eventhough the level of detectable polymorphism is quite low.

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Maria José Aranzana, Joaquim Carbó, and Pere Arús

A sample of 210 cultivars of Prunus persica (L.) Batsch, with a wide range of fruit and plant characteristics, was studied for variability using nine polymorphic amplified fragment length polymorphism (AFLP) primer combinations. Forty-seven AFLPs allowed identification of 196 (93%) different genotypes, 187 of which could be distinguished with three primer combinations. Eleven cultivars with the same AFLP phenotype corresponded to known somatic mutations (sports), but from the four sports of the `Springcrest' group, two (`Maycrest' and `Queencrest') differed at three AFLPs from the others (`Starcrest' and `Early Maycrest'). Cluster analysis allowed differentiation of most cultivars with nonmelting fruit flesh, generally used for canning, from the melting-flesh peach and nectarine cultivars used for fresh consumption.

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Maureen C. O'Leary and Thomas H. Boyle

Cultivars and seedlings of Rhipsalidopsis and Schlumbergera were subjected to isozyme analysis using seven enzyme systems [aspartate aminotransferase (AAT), aminopeptidase (AMP), glucose-6-phosphate isomerase (GPI), malate dehydrogenase (MDH), phosphoglucomutase (PGM), shikimate dehydrogenase (SKD), and triose phosphate isomerase (TPI)]. Isozymes were extracted from phylloclades and roots, and were separated by polyacrylamide gel electrophoresis (PAGE) using single percentage (5% to 10%) gels. Six enzymes exhibited polymorphism in Rhipsalidopsis, whereas all seven enzymes were polymorphic in Schlumbergera. Inheritance studies were performed on AAT, GPI, MDH, PGM, and TPI for Rhipsalidopsis and on AMP, PGM, and SKD for Schlumbergera. Significant segregation distortion was observed in some families. Polymorphic isozymes are potentially useful markers for cultivar identification and for genetic and breeding studies.

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Antonio Figueira, Jules Janick, and Peter Goldsbrough

The size of the haploid genome of Theobroma cacao L. (cacao), estimated using laser flow cytometry, was 0.43 pg. An improved DNA extraction procedure was developed based on isolation of a crude nuclei preparation from leaf tissue that effectively eliminated contamination of the DNA by polysaccharides and produced DNA that was, on average, longer than 50 kb. DNA yields ranged from 2 to 10 μg·g-1 fresh weight of leaf tissue. DNA blot hybridization experiments with a flax (Linum usitatissimum L.) ribosomal DNA probe revealed restriction fragment length polymorphisms between three cacao genotypes. Differences between the DNA of these genotypes were also detected by polymerase chain reaction amplification of polymorphic DNA fragments, using random oligonucleotide primers.

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Unaroj Boonprakob and David H. Byrne

Diploid plums such as Prunus salicina, P. simonii, P. cerasifera, P. americana, P. angustifolia, P. mexicana, and their hybrids have a high level of RAPD polymorphisms. Of 71 successfully used primers, there are 417 reproducible RAPD markers and only 55 (13%) markers are not polymorphic. Genetic relationships of these diploid plums based on RAPD data is estimated using genetic distance (GD) defined as GDij = 1 – Sij, where Sij is similarity coefficient. Two similarity coefficients, Jaccard's and simple matching coefficient, are compared. Simple matching always yields higher similarity coefficients. Genetic distance within and between each gene pool: California, southeastern U.S., foreign, is estimated. Genetic distances of these diploid plums ranged from 0.32 to 0.68, and agreed well with the natural geographic distribution of the species. The cluster analysis using unweighted pair-group methods using arithmetic averages (UPGMA) was used to construct phenograms to summarize the relationships among these cultivated diploid plums and plum species.

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Pei Xu, Tingting Hu, Yuejian Yang, Xiaohua Wu, Baogen Wang, Yonghua Liu, Dehui Qin, Jeffrey Ehlers, Timothy Close, Zhongfu Lu, and Guojing Li

white flowers were associated with cream/white seedcoat in general. A general flower color factor C has been mapped onto the fourth linkage group of ssp. unguiculata based on amplified fragment length polymorphism (AFLP) markers ( Menéndez et al., 1997