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Zhan Shu, Xue Zhang, Dianqiong Yu, Sijia Xue, and Hua Wang

complex introgression as backcrosses, F 2 s, etc. ( Hoban et al., 2009 ). For these reasons, hybrids are often difficult to distinguish by silvic characters, and identification using DNA markers is essential. Simple sequence repeat (SSR) markers exhibit

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Gad G. Yousef, Mary A. Lila, Ivette Guzman, James R. Ballington, and Allan F. Brown

, V. angustifolium, and V. virgatum ) and (increasingly) to transfer unique genes or chromosomal segments (introgressions) from the secondary gene pool (non-cultivated Cyanococcus species) ( Ballington, 2009 ; Brevis et al., 2008 ). However

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Isabelle Y. Delannay, Jack E. Staub, and Jin Feng Chen

. sativus yield or quality can also be introduced during introgression of the C. hystrix genome. The inbred backcross breeding method ( Wehrhahn and Allard, 1965 ) has shown potential for improving population diversity and yield among cucumbers ( Owens

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Matthew Chappell, Carol Robacker, and Tracie M. Jenkins

to measure introgression in a hybrid swarm located at Stone Mountain, GA. Morphological markers were used to confirm results and measure the level of introgression within the population. In the hybrid population of R. canescens and R. flammeum

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Mariola Plazas, Santiago Vilanova, Pietro Gramazio, Adrián Rodríguez-Burruezo, Ana Fita, Francisco J. Herraiz, Rajakapasha Ranil, Ramya Fonseka, Lahiru Niran, Hemal Fonseka, Brice Kouassi, Abou Kouassi, Auguste Kouassi, and Jaime Prohens

very limited ( Daunay and Hazra, 2012 ; Rotino et al., 2014 ), and no commercial cultivars containing introgressions from wild-related species are known to us. Depending on phylogenetic relationships and crossability with eggplant, wild relatives are

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Ockyung H. Bark, Michael J. Havey, and Joe N. Corgan

The edible Alliums are economically important world-wide. The bulb onion (Allium cepa) is the most widely grown. The Japanese bunching onion (A. fistulosum) has many desirable characters, e.g., resistance to pink root, Thrips, smut, maggot, and Botrytis. Transfer of pink root resistance from A. fistulosum into A. cepa has been attempted for over 60 years. However, sterility of the F1 hybrid is a barrier and there is little evidence of gene introgression during backcrossing to A. cepa. Dr. Corgan has made crosses between A. fistulosum as the seed parent and A. cepa. He backcrossed the F1 hybrids to A. cepa and generated BC2 progenies which showed excellent pink root resistance. RFLPs in the chloroplast genome showed all BC2 progenies had either the normal or sterile cytoplasm of A. cepa. This may be due to not strictly maternal inheritance of the chloroplast DNA or a seed mixture during backcrossing. Other interspecific hybrids and their BC1 progenies had the cytoplasm of A. fistulosum. Nuclear RFLPs show hybrid patterns in the F1 plants. BC1 progenies possess some A. fistulosum markers as evidence of DNA introgression from A. fistulosum into the backcross progenies.

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Robert H. Bors and J. Alan Sullivan

Fragaria species from the center of diversity have not been integrated into octoploid commercial strawberry cultivars because of ploidy level differences. Even though traits such as disease resistance, enhanced flavor, cold hardiness, and vigor are known to exist in the diploid, tetraploid, and hexaploid species, they cannot be easily used for breeding. The synthetic octoploid method circumvented introgression difficulties by combining lower ploidy species and doubling to the octoploid level. Although easily crossed to cultivars, the use of synthetic octoploids has been minimal as it has been extremely difficult to create them. By working to improve bottlenecks of the original system, improved methodology has been developed and 170 synthetic octoploids have been produced. This represents more than a 100-fold increase in efficiency. The following factors played a major role in improving the system: wide germplasm base; use of F. vesca as a common genome; embryo rescue; 5% colchicine applied in vitro by dropper method for 24 hours followed by a quick rinse and continuous light in a 18C growth chamber. F. vesca, F. nilgerrensis, F. nubicola, F. viridis, F. orientalis, and F. moschata have been incorporated into synthetic octoploids in this study.

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Keith Woeste, Gale McGranahan, and Robert Bernatzky

A first backcross population of walnuts {[Juglans hindsii (Jeps.) Jeps. × Juglans regia L.] × J. regia} was used to evaluate the correlation between morphological (statistical) and genetic distance during introgression. Five traits based on leaf morphology were identified to quantitate the morphology of the parental species, their F1 hybrids, and the backcrosses to each parent. These traits were used to evaluate the morphological similarity of first backcrosses to J. regia using Mahalanobis' distance. The amount of genomic introgression of each backcross was estimated using 59 randomly amplified polymorphic DNA (RAPD) and 41 restriction fragment-length polymorphism (RFLP) genetic markers that identify polymorphisms between J. regia and J. hindsii. A smaller scaffold set of markers was also identified using published linkage data. The correlation between the measures of morphological and genomic introgression for the first backcrosses was low (0.23) but significant. The results suggest that selection based on morphology during backcrossing will not be an effective way to recover recurrent parent genome.

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Anfu Hou and Ellen B. Peffley

Introgression of genes in species crosses can be observed morphologically in backcrossed or selfed progenies, but the phenotype does not give information about the movement of DNAs. Cytogenetic markers allow for visualization of specific DNAs in a genome. Few cytogenetic markers are available in onion to monitor the introgression of DNA in species crosses. Genomic in situ hybridization (GISH) provides a way to locate unique DNA sequences contributed by parents. We are using GISH to monitor the movement of DNAs from A. fistulosum into A. cepa. Results of experiments using A. fistulosum as probe DNA, and A. cepa as blocking DNA will be reported. Also presented are hybridization sites observed in F1BC3 progeny of the GISH.

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John R. Stommel, Ruth S. Kobayashi, and Stephen L. Sinden

Somatic fusion hybrids created between tomato and Solanum ochranthum, a wild nontuber-bearing diploid species that is genetically isolated from tomato, were evaluated in an effort to introgress traits from S. ochranthum into tomato. Pollen stainability and pollen tube growth examination demonstrated that little or no viable pollen was present in tetraploid and hexaploid fusion hybrids. Aneuploidy was noted in a small percentage of these hybrids. Use of tetraploid and hexaploid fusion hybrids as female parents in backcrosses to diploid and tetraploid tomato was studied. Chemical treatments that induce either chromosomal recombination or reduction may be advantageous for overcoming difficulties in introgression of these wide hybrids into tomato.