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Xianping Qu, Jiang Lu and Olusola Lamikanra

Two morphologically distinct types of grapes belonging to the subgenera Euvitis and Muscadinia in the genus Vitis are cultivated in the United States. The former is commonly called bunch grapes while the latter is usually called muscadine. Genetic diversity among these grapes was investigated using RAPD markers. Sixteen grape cultivars, with parentage including V. rotundifolia Michx., V. vinifera L., and several American Vitis species, were used for the RAPD analysis. A total of 156 RAPD markers was produced from 19 random primers, over 90% of which was polymorphic among the muscadine and the bunch grapes. Polymorphisms were lower within each subgenus. Relationships between these two subgenera were estimated based on band-sharing and cluster analysis. The average genetic distance between the bunch and the muscadine grape cultivars was 0.45. The results based on DNA analysis agree with isozyme data obtained from a separate study, which demonstrated that muscadine grapes share very few common alleles with American bunch grapes and European grapes.

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Jiang Lu, Xianping Qu and Olusola Lamikanra

Two morphologically very distinct grapevines belonging to the subgenera Euvitis and Muscadinia of the genus Vitis are cultivated in the United States. The former is commonly called “bunch” grape, while the latter is usually called “muscadine.” Genetic diversity among these grapes was investigated based on random amplified polymorphic DNAs (RAPDs). Sixteen grape cultivars, with their parentage including V. rotundifolia, V. vinifera, and several American Vitis species, were used for the RAPD analysis. More than 200 RAPDs were produced from 20 random primers. More than 90% of which were polymorphic between the muscadine and the bunch grapes, while polymorphism was considerably low within the muscadine and the bunch grapes. The relationships of grapes between these two subgenera were estimated based on bandsharing and cluster analysis. The result based on the DNA analysis agrees with the isozyme data obtained from a separate study, which demonstrated that the muscadine grape shares very low common alleles with the American bunch grapes and the European grapes.

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Ying Wang, Gregory L. Reighard, Desmond R. Layne, Albert G. Abbott and Hongwen Huang

Pawpaw (Asimina triloba) produces the largest fruit native to the United States. Six linkage groups were identified for A. triloba using the interspecific cross [PPF1-5 (A. triloba) × RET (A. reticulata Shuttlw. ex Chapman)], covering 206 centimorgans (cM). A total of 134 dominant amplification fragment length polymorphism (AFLP) markers (37 polymorphic and 97 monomorphic) were employed for estimating the genetic diversity of eight wild populations and 31 cultivars and advanced selections. For the wild populations, the percentage of polymorphic loci over all populations was 28.1% for dominant markers and Nei's genetic diversity (He) were 0.077 estimated by 134 dominant markers. Genetic diversity and the percentage of polymorphic loci estimated using only polymorphic dominant AFLPs were 0.245 and 79%, respectively, which are comparable with other plant species having the same characteristics. Estimated genetic diversity within populations accounted for 81.3% of the total genetic diversity. For cultivars and advanced selections, genetic diversity estimated by 134 dominant markers was similar to that of wild pawpaw populations (He = 0.071). Thirty-one cultivars and advanced selections were delineated by as few as nine polymorphic AFLP dominant loci. Genetic relationships among wild populations, cultivars and advanced selections were further examined by unweighted pair group method with arithmetic mean (UPGMA) of Nei's unbiased genetic distance. The genetic diversity estimated for wild populations using the clustered polymorphic markers was lower than the result estimated using the nonclustered polymorphic markers. Therefore, this study indicates that the number of sampled genomic regions, instead of the number of markers, plays an important role for the genetic diversity estimates.

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Hyo-Won Seo, Jung-Yoon Yi, Eung-Soo Kim, Hyun-Mook Cho, Young-Eun Park and Kuen-Woo Park

This study was carried out to prove the new variety's originality by using Random Amplified Polymorphic DNA (RAPD) Analysis and to develope the specific markers for distinction new variety from others to database for improving the efficiency of germplasm conservation. The RAPD procedure was used to determine genetic diversity of 13 potato varieties including seven recommended varieties of Korea and six genotypes. Genomic DNAs from the 13 genotypes were amplified using PCR and URP 2F, 4R and 8R primers. URP primers which were 20-mers were received from NIAST (National Institute of Agricultural Science and Technology, Suwon, Korea) and they were shown very high reproducibility because of the high annealing temperature above 55 °C. So, they were known to be very desirable primers to examine the specificity between inter and intra species in various spectra. These 13 lines have many resemblances in plant characteristics each other because `Jopung', '92N09-6', `Daekwan 68', and `Daekwan 70' were originated from `Superior', `Atlantic', `Namsuh', and `Irish Cobbler' respectively. So, there are many difficulties to distinct new variety by the naked eye. The results of this study show that 2 sets of URP primers are very useful to distinct new variety and mutants from others.

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A. del Rio, J.B. Bamberg, Z. Huaman, R. Hoekstra, A. Salas and S.E. Vega

Effects of genebank seed increases on the genetic integrity and whether germplasm in the genebank still represents the in situ populations from which it was collected are major concerns of the recently formed Association of Potato Intergenebank Collaborators (APIC), a consortium of world potato genebank leaders. This cooperative APIC research used RAPDs and morphological markers 1) to establish genetic relationships between seed increased populations within accessions and (2) to measure genetic differentiation between diploid and tetraploid potato germplasm maintained for many years and current in situ populations from the same collection sites in the wild. Solanum jamesii Torrey (2n = 2x = 24) and S. fendleri A. Gray (2n = 4x = 48), two wild potato species native to North America, were used as plant material. These species represented two major breeding systems found among Solanum species: outcrossing diploids and inbreeding disomic tetraploids, respectively. Comparisons made between populations one generation apart and between sister populations generated from a common source indicated that there has been minimal loss of genetic diversity in captive germplasm using the genebank techniques standard at NRSP-6 and other world potato genebanks. RAPD markers also revealed that significant genetic differences were found between genebank-conserved and re-collected in situ populations for all diploid potato comparisons and for about half of the comparisons within tetraploid potato populations.

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Lianghong Chen, Shizhou Wang and Mack Nelson

In this study research was conducted to evaluate the feasibility of characterizing genetic variation within camellia species using random amplified polymorphic DNAs (RAPD) markers. Eight varieties of species Camellia japonica and four varieties of species Camellia reticulata, provided by the America Camellia Society, Fort Valley, Ga., were investigated. RAPD profiles generated by five selected 10-based random primers (out of 20 primers) exhibited distinct patterns of amplified bands for all 12 tested varieties. A total of 344 bands were produced among the eight varieties of species C. japonica, with an average of 8.6 bands, ranging from 220 to 2072 bp in size, scored per primer. Among the 344 amplified bands, 74.4% of the bands presented polymorphic. The four varieties of species C. reticulata produced a total of 180 markers, with an average percentage of 57.8% polymorphisms. The amplified bands were in the range of 236–1760 bp. An average of nine amplified bands was generated per primer. The large percentages of polymorphisms displayed among 12 varieties within the two different species indicate that the expected genetic diversity among varieties within camellia species existed. It was concluded that the RAPD molecular markers are capable of revealing appreciable levels of genetic variation within camellia species.

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N. Nikoloudakis, G. Banilas, F. Gazis, P. Hatzopoulos and J. Metzidakis

Random amplified polymorphic DNA (RAPD) markers were used to study the genetic diversity and to discriminate among 33 Greek olive (Olea europaea L.) cultivars. Three feral forms from Crete and five foreign cultivars recently introduced into Greece were also included. Nineteen primers were selected which produced 64 reproducible polymorphic bands in the 41 olive genotypes studied, with an average of 3.4 informative markers per primer. The RAPD markers resulted in 135 distinct electrophoretic patterns, with an average of 7.1 patterns per primer. Based on either unique or combined patterns, all genotypes could be identified. Genetic similarities between genotypes were estimated using the Dice similarity index and these indicated that a high degree of diversity exists within the Greek olive germplasm. Using the unweighted pair-group method (UPGMA) most cultivars were clustered into two main groups according to their fruit size or commercial use (table or olive oil). However, poor correlation was detected between clustering of cultivars and their principal area of cultivation. RAPD marker data were subjected to nonmetric multidimentional scaling (NMDS) which produced results similar to those of the UPGMA analysis. The results presented here contribute to a comprehensive understanding of cultivated Greek olive germplasm and provide information that could be important for cultural purposes and breeding programs.

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Anfu Hou, James R. McFerson and Warren F. Lamboy

Molecular DNA markers based on the RAPD (random amplified polymorphic DNA) assay are gaining use in germplasm assessment. RAPD markers are simple, relatively inexpensive, and highly informative. We used five primers to assess 26 Brassica oleracea breeding lines from the IVF and nine accessions from the PGRU. The test array included eight subspecies of B. oleracea. We generated 90 RAPD markers and were able to unambiguously discriminate among all 35 test entries, but could not separate subspecies within B. oleracea. Genetic similarity between subspecies ranged from 0.629 to 0.738. Average similarity within accessions was 0.96, confirming the suspected homogeneity of breeding lines. Nevertheless, significant genetic diversity was found among kohlrabi, broccoli, and cabbage accessions. Similarity analysis of breeding lines and hybrids confirmed their pedigree relationships. Interestingly, B. o. subsp. costata `Couve Nabica' showed closer similarity to B. napus subsp. oleifera `Jet Neuf' than to other B. o. materials and B. o. subsp. italica `Packman' showed higher similarity to some cabbages than to other broccolis. Results provide further evidence that diversity assessment using RAPDs is broadly applicable and useful in germplasm conservation and utilization.

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R.J. Schnell, J.S. Brown, C.T. Olano, A.W. Meerow, R.J. Campbell and D.N. Kuhn

Mango (Mangifera indica L.) germplasm can be classified by origin with the primary groups being cultivars selected from the centers of diversity for the species, India and Southeast Asia, and those selected in Florida and other tropical and subtropical locations. Accessions have also been classified by horticultural type: cultivars that produce monoembryonic seed vs. cultivars that produce polyembryonic seed. In this study we used 25 microsatellite loci to estimate genetic diversity among 203 unique mangos (M. indica), two M. griffithii Hook. f., and three M. odorata Griff. accessions maintained at the National Germplasm Repository and by Fairchild Tropical Botanic Garden in Miami, Fla. The 25 microsatellite loci had an average of 6.96 alleles per locus and an average polymorphism information content (PIC) value of 0.552 for the M. indica population. The total propagation error in the collection (i.e., plants that had been incorrectly labeled or grafted) was estimated to be 6.13%. When compared by origin, the Florida cultivars were more closely related to Indian than to Southeast Asian cultivars. Unbiased gene diversity (Hnb) of 0.600 and 0.582 was found for Indian and Southeast Asian cultivars, respectively, and both were higher than Hnb among Florida cultivars (0.538). When compared by horticultural type, Hnb was higher among the polyembryonic types (0.596) than in the monoembryonic types (0.571). Parentage analysis of the Florida cultivars was accomplished using a multistage process based on introduction dates of cultivars into Florida and selection dates of Florida cultivars. In total, 64 Florida cultivars were evaluated over four generations. Microsatellite marker evidence suggests that as few as four Indian cultivars, and the land race known as `Turpentine', were involved in the early cultivar selections. Florida may not represent a secondary center of diversity; however, the Florida group is a unique set of cultivars selected under similar conditions offering production stability in a wide range of environments.

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Raymond Schnell, J. Steven Brown, Cecile Olano, Alan Meerow, Richard Campbell and David Kuhn

Mangifera indica L. germplasm can be classified by origin with the primary groups being cultivars selected from the centers of diversity for the species, India and Southeast Asia, and those selected in Florida and other tropical and subtropical locations. Accessions have also been classified by horticultural type: cultivars that produce monoembryonic seed vs. cultivars that produce polyembryonic seed. In this study, we used 25 microsatellite loci to estimate genetic diversity among 203 accessions. The 25 microsatellite loci had an average of 6.96 alleles per locus and an average PIC value of 0.552. The total propagation error in the collection, i.e., plants that had been incorrectly labeled or grafted, was estimated to be 6.13%. When compared by origin, the Florida cultivars were more closely related to Indian than to Southeast Asian cultivars. Unbiased gene diversity (Hnb) of 0.600 and 0.582 was found for Indian and Southeast Asian cultivars, respectively, and both were higher than Hnb among Florida cultivars (0.538). When compared by horticultural type, Hnb was higher among the polyembryonic types (0.596) than in the monoembryonic types (0.571). Parentage analysis of the Florida cultivars was accomplished using a multistage process based on introduction dates of cultivars into Florida and selection dates of Florida cultivars. Microsatellite marker evidence suggests that as few as four Indian cultivars, and the land race known as `Turpentine', were involved in the early cultivar selections. Florida may not represent a secondary center of diversity; however, the Florida group is a unique set of cultivars selected under similar conditions offering production stability in a wide range of environments.