values can reveal genetic distance populations ( Table 2 ). It ranged from 0.074 between Pop IA (American and East Asian ecotype mixed) and Pop IIA (American ecotype) to 0.341 between Pop IB (East Asian ecotype) and Pop IIB (wild species mixed
Haiying Zhang, Jianguang Fan, Shaogui Guo, Yi Ren, Guoyi Gong, Jie Zhang, Yiqun Weng, Angela Davis, and Yong Xu
Robert G. Fjellstrom and Dan E. Parfitt
RFLPs were studied in 41 populations of 13 Juglans species to study genetic diversity and phylogenetic relationships. 19 single locus nuclear RFLP loci were used to generate genetic distance/identity matrices based on allele frequencies. 21 probes were used to generate genetic distances and phylograms using shared-fragments with parsimony analysis. Parsimony analysis on fragment data produced a minimal length tree in general agreement with distance data trees, but with additional phylogenetic resolution resembling previous systematic studies. All analyses indicate an ancient origin of J. regia, which has been considered a recently derived species. A 10x difference in heterozygosity was seen among species. Genetic differentiation among conspecific east Asian populations was larger than among east Asian species. The opposite was true for American species. J. hindsii is classified as a distinct species and J. cinerea was included in section Cardiocaryon rather than Trachycaryon, from the diversity analysis.
Hongwen Huang, Fenny Dane, and Joseph Norton
Allozyme genetic variability in three chestnut (Castanea) species was investigated using 19 loci from ten enzyme systems. G-tests of heterogeneity of isozymic allele distribution showed significant differences in both intraspecific and interspecific populations. C. mollissima was found to possess a significantly higher value of mean gene heterozygosity (H=0.3050±0.0419), percentage of polymorphic loci (P=84.21%) and average number of alleles per locus (A=2.05) than any other species in the Castanea section Eucustanon. When the genetic variability of populations of C. mollissimo from four regions in China was investigated, population from the Changjiang river region showed a markedly higher mean gene heterozygosity (H=0.3480±0.0436) than populations from the other regions. An approximately identical genetic distance between the population from the Changjiang river region and populations from three other regions was observed, while populations from the latter regions showed almost the same genetic distance from each other.
M.C. Scott, G. Caetano-Anollés, and R.N. Trigiano
The genetic distance of closely related cultivars of Dendranthema grandiflora (chrysanthemum) was assessed using DAF. Thirteen cultivars of chrysanthemum included in the study were members of the following series: Charm (five), Davis (four), and Pomona (four). The genetic variability within and between series were evaluated using 11 arbitrary octamer primers. A few polymorphic loci were evident that uniquely identified closely related cultivars within a series. In contrast, there were many polymorphisms between members of different series. Genetic distances between cultivars within and between series were calculated using marker comparison and UPGMA (cluster analysis). The average distance between series was 10-fold greater than between cultivars within a series. DNA from all cultivars belonging to a series also were bulked to generate DNA profiles containing unique amplified products for each series. Polymorphic loci that were generated by the DAF technique possibly could be used for patent protection and phylogenetic studies and may be useful in breeding for chrysanthemums.
Ajay Nair, Donglin Zhang, and Dogyan Hu
The natural distribution and cultivated areas of Stewartia taxa are USDA cold hardiness zones 6 or warmer. One cold-tolerant clone, named Stewartia`UMaine' (UMaine Silk Camellia), has been growing well at the University of Maine Littlefield Ornamentals Trial Garden (USDA Zone 4). The plant also has brilliant red fall color and biennial flowering. Since cold hardiness field evaluation could not provide genetic information and no other taxa could grow in Zone 4, AFLP markers were employed to figure out its genetic relativeness with other 16 named Stewartia taxa. The three primer-pairs generated 360 useful markers with an average of 120 markers for each taxon. The genetic distance between S. sinensis and S. rostrata is only 0.031, which indicates that these two species are very similar and should not be treated as two species or cultivars, at least the plants in cultivation. The largest distance (0.533) occurs between S. pesudocamellia and S. malacodendron, two distinguished species accepted by all taxonomists. UMaine Silk Camellia is a distinguished taxon from all other 16 taxa and S. malacodendron `Delmarva' has the largest genetic distance of 0.453 to it. Although S. ×henryae`Skyrocket' has the smallest genetic distance of 0.183 to Stewartia`UMaine', UPGMA phenograms showed that they are not in a clad at all. AFLP data support that Stewartia`UMaine' is a new cultivar, which originated from a gene pool of S. pseudocamellia, S. sinensis, and S. koreana. These molecular results will also be used as guidance for future Stewartia breeding.
M.M. Paz and R.E. Veilleux
RAPD analysis was conducted on in vitro plantlets of Solanum phureja Juz. & Buk. monoploids and diploid heterozygous pollinators. Among 60 decamer primers screened, 11 did not show polymorphism while some primers produced complex banding patterns or faint bands that were difficult to score. Genetic distance estimates were based on 151 polymorphic RAPD markers of 208 bands scored using 33 primers. Simple matching and Jaccard coefficients were calculated to estimate genetic similarity (GS). Genetic distance (GD=1-GS) among genotypes ranged from 0.0 to 0.664. Cluster analysis yielded groups of genotypes that were consistent with known genomic compositions or genetic relationships inferred from their pedigree. Field evaluation of 14 F1 families resulting from five S. phureja doubled monoploids (DMs) crossed to three heterozygous pollinators (IDs) revealed significant differences in total tuber number, total tuber yield, average tuber mass, and vigor. Total tuber yield per family ranged from 174 to 404 g per plant and was significantly lower than the control `Kennebec'. The general combining ability of DM BARD 13-14/202 was superior to other DM parents. Specific combining ability was observed in progeny of AD2-4/3s.8 H ID 4. Among male parents, ID 8 performed better than ID 4 or ID 5. Using simple matching, the largest parental genetic distance was always associated with the highest total tuber yield among progenies of DM parents. A similar trend was obtained using Jaccard coefficients. Based on our results, RAPD markers may facilitate the identification of diverse parents to maximize the expression of heterosis in S. phureja hybrids.
Michael J. Havey
Restriction fragment length polymorphisms (RFLPs) in the chloroplast and nuclear genome are useful for estimation of phylogenetic relationships. Fifteen mutations at restriction enzyme sites in the chloroplast DNA were discovered. The wild species A. oschaninii and A. vavilovii were identical to A. cepa for all mutations. These species represent sources of wild germplasm closely related to the bulb onion. Nuclear RFLPs are now being used to estimate the genetic distances between accessions of A. oschaninii A. vavilovii, and open-pollinated populations of the cultivated bulb onion.
Claudia Cunha, Tana Hintz, and Phillip Griffiths
DNA extractions from 77 snap bean and 2 dry bean cultivars were evaluated for molecular polymorphisms. In total, 100 10-mer oligonuceotide primers were evaluated, and 31 primers that amplified clear and repeatable polymorphisms among bean cultivars were selected. These primers amplified a total of 49 polymorphisms between the cultivars and were used to differentiate the cultivars and evaluate the genetic diversity between them. All cultivars were clustered according to genetic similarities using GenStat 5.0 software, and groupings of pod types were observed when cultivars were separated based on a dissimilarity index. The RAPD polymorphisms will be useful for cultivar determination, seed purity testing and estimation of genetic distances.
Eric Stafne*, John Clark, and Allen Szalanski
In this study, the nuclear ribosomal DNA internal transcribed spacer region (ITS) of six Rubus cultivars were sequenced, then compared with sequences of three Rubus species in Genbank. DNA sequencing revealed little genetic variation among blackberry cultivars, but ably revealed distinctions between blackberry and red raspberry genotypes. Analysis by maximum-parsimony and pairwise genetic distances confirmed the small variation among blackberry cultivars. The resulting sequences were analyzed for useful restriction sites and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis was conducted on a total of six cultivars to establish genetic variation. Digests were difficult to interpret due to heterogeneity at restriction sites.
A.L. Fenwick and S.M. Ward
Seventeen mint accessions representing the three species grown for commercial oil production in the United States were characterized using randomly amplified polymorphic DNA (RAPD) analysis. The RAPD profiles readily identified the different Mentha species; calculation of genetic distance, based on the number of shared bands, indicated that M. spicata L. is more closely related to M. × gracilis than to M. × piperita. The RAPD profiles also distinguished among eight peppermint accessions of different geographical origin. However, only limited polymorphism was observed among the most widely grown peppermint and Scotch spearmint cultivars. These results indicate a potential lack of genetic diversity in mint cultivars grown for oil in the United States.