Molecular analysis of genetic diversity in melon landraces (<Emphasis Type="Italic">Cucumis</Emphasis><Emphasis Type="Italic">melo</Emphasis> L.) from Myanmar and their relationship with melon germplasm from East and South Asia

Genetic diversity of Myanmar melon was evaluated by analysis of 27 RAPD markers and morphological characters using 41 accessions of melon landraces of which 36 accessions were small-seed type. The gene diversity was 0.239, higher than for group Conomon from East Asia and equivalent to Indian melon populations. Melon accessions were classified into six major clusters. The largest cluster IV comprised mainly group Conomon which was closely related to cluster V consisting of mainly group Agrestis. Most of the accessions of group Cantalupensis were grouped into clusters II or VII and were distantly related to groups Conomon and Agrestis. The genetic relationship to melon accessions from neighboring countries was analyzed. The 24 accessions of clusters IV and V were mostly clustered together with small-seed type melon of India, but the 14 accessions of clusters VI and VII were mostly clustered together with large-seed type melon of India. These results indicated that the genetic diversity of Indian melon is conserved in Myanmar. Genetic introgression among melon groups through spontaneous hybridization was also indicated and was considered important to maintain or increase the genetic diversity in Myanmar.     

Genetic structure and diversity of India hybrid tea

The most important evolutionary event in the success of commercial tea cultivation outside China in ~30 countries came about by the origin of India hybrid tea in India, derived from the extensive spontaneous hybridization that took place between the Assam type tea growing in the forest regions of Assam, North-East India and China type tea introduced from China in ~1875 to many regions of North-East India. The release of an enormous pool of vigorous and highly variable plants of India hybrid tea in North-East India was a significant step forward for the origin and evolution of tea as a highly successful crop plant. The 1,644 accessions and clones of India hybrid tea, representatives of known 15 morphotypes, were screened by 412 AFLP markers amplified by 7 AFLP primer pair combinations. All the 412 genetic loci were polymorphic across the 1,644 accessions and clones. The analysis was done with distance (PCoA and NJ) methods, and the STRUCTURE (Bayesian) model. Both PCoA and NJ analysis clustered 1,644 tea accessions and clones into six major groups with one group in each, constituted mostly by China hybrid, Assam China hybrid and Assam hybrid morphotypes, of distinct genetic identity. No group was exclusive for any particular morphotype. The accessions and clones belonging to morphotypes, Assam type, Assam hybrid, China hybrid and China Cambod were distributed in all the groups. It is the Assam type/Assam hybrid morphotypes which exhibit much broader genetic variability than in China type/China hybrid/Cambod type/Cambod hybrid morphotypes. The STRUCTURE analysis inferred 16 populations (K = 16), for which the greatest values of probability were obtained. Nine of the 16 clusters were constituted by the tea accessions and clones of ‘pure’ ancestry. The remaining clusters were of ‘mixed’ ancestry. This analysis provides evidence that the accessions and clones of the same morphotype are not always of same genetic ancestry structure. The tea accessions and clones obtained from outside North-East India shared the same groups (distance method) and clusters (STRUCTURE model) which were constituted by North-East India accessions. The present study also demonstrates very narrow genetic diversity in the commercial tea clones vis-à-vis the profound genetic diversity existing in the tea accessions. These clones were distributed in hardly two of the six groups in NJ tree. The identified 105 core accessions and clones, capturing 98% diversity, have their origin from almost all groups/subgroups of NJ tree.     

Analysis of genetic diversity in a sweet potato (Ipomoea batatas L.) germplasm collection from Tanzania as revealed by AFLP

Sweet potato (Ipomoea batatas L.) is the fifth most important crop in the developing countries after rice, wheat, maize and cassava. The amplified fragment length polymorphism (AFLP) method was used to study the genetic diversity and relationships of sweet potato accessions in the germplasm collection of Sokoine University of Agriculture, Morogoro and Sugarcane Research Institute, Kibaha, Tanzania. AFLP analysis of 97 sweet potato accessions using ten primer combinations gave a total of 202 clear polymorphic bands. Each one of the 97 sweet potato accessions could be distinguished based on these primer combinations. Estimates of genetic similarities were obtained by the Dice coefficient, and a final dendrogram was constructed with the un-weight pair-group method using arithmetic average. AFLP-based genetic similarity varied from 0.388 to 0.941, with a mean of 0.709. Cluster analysis using genetic similarity divided the accessions into two main groups suggesting that there are genetic relationships among the accessions. Principal Coordinate analysis confirmed the pattern of the cluster analysis. Analysis of molecular variance revealed greater variation within regions (96.19%) than among regions (3.81%). The results from the AFLP analysis revealed a relatively low genetic diversity among the germplasm accessions and the genetic distances between regions were low. A maximally diverse subset of 13 accessions capturing 97% of the molecular markers diversity was identified. We were able to detect duplicates accessions in the germplasm collection using the highly polymorphic markers obtained by AFLP, which were found to be an efficient tool to characterize the genetic diversity and relationships of sweet potato accessions in the germplasm collection in Tanzania.     

青藏高原野生老芒麦种质醇溶蛋白遗传多样性分析

采用酸性聚丙烯酰胺凝胶电泳(A-PAGE) 对采集自青藏高原的54份野生老芒麦（Elymus sibiricus L.）种质进行遗传多样性分析,获得下述结果:（1）供试材料共分离出42条带纹,多态率达92.86%。4个电泳分区（α、β、γ、ω）的平均Shannon指数为0.4627,Nei-Li遗传相似系数（GS）变异范围为0.2424~0.9767,平均值为0.5822。说明供试野生老芒麦材料具有较为丰富的醇溶蛋白遗传多样性。（2）对所有材料的聚类分析和主成分分析发现,在GS值为0.562的水平上供试材料可聚成4个大类,绝大部分来自于相同或相似生态地理环境的材料聚成一类,主成分分析显示了相似的结果,即醇溶蛋白图谱类型与材料的生态地理环境具有一定的相关性。（3）基于Shannon 多样性指数估算了5个老芒麦地理类群内和类群间的遗传分化,发现类群内遗传变异占总变异的68.17%,而类群间的遗传变异占总变异的31.83 %。（4）对各地理类群基于Nei氏无偏估计的遗传一致度的聚类分析表明,各地理类群间的遗传分化与其所处的地理生态环境具有较高的相关性。     

Genetic diversity and population structure of worldwide eggplant (<Emphasis Type="Italic">Solanum melongena</Emphasis> L.) germplasm using SSR markers

Two hundred and eighty-seven worldwide eggplant accessions were examined for genetic diversity and population structure analysis with 45 SSR markers. The results resolved 242 alleles across all the accessions. Gene diversity ranged from 0.104 to 0.832 with an average of 0.558. Polymorphic information content ranged from 0.102 to 0.815 with an average of 0.507. The genetic diversity analysis classified all accessions into four groups, and the data showed that gene exchanges occurred in two groups during germplasm introduction, domestication, and improvement; however, the frequency was low. Population structure analysis classified 269 accessions into two subgroups, and the remaining 18 accessions were defined as admixed. The accessions from the same geographic origin tend to be clustered into same group. These results provide new insights into the exploitation of genetic diversity of germplasm for eggplant breeding program.     

Genetic diversity comparison between Chinese and Japanese soybeans (<Emphasis Type="Italic">Glycine max</Emphasis> (L.) Merr.) revealed by nuclear SSRs

Soybean (Glycine max (L.) Merr.) has a long planting history in both China and Japan. In order to investigate the genetic relationship between Chinese and Japanese soybeans, 205 Chinese soybean accessions, that represent the seven different soybean ecotypes, and 39 Japanese soybean accessions from various regions were analyzed by using 46 SSR loci. In total 745 alleles were detected with an average allele number of 16.2 per locus. The allelic frequencies varied from 0.002 to 0.554 with an average of 0.06. Cluster analysis with UPGMA separated the Chinese accessions from Japanese accessions, suggesting that soybean in these two countries form different gene pools. When comparing the Japanese soybean with that from seven different Chinese soybean ecotypes, 164–200 alleles were specific to the Chinese accessions and 64–112 specific to the Japanese accessions. The comparison of SSRs diversity revealed that accessions from China exhibited more genetic diversity than those from Japan. The data were analyzed to resolve the genetic structure and to interpret the evolutionary relationships between groups. Three distinct groups were identified, corresponding to Japanese soybean, Northern China soybean, Southern China soybean and a mixed group in which most accessions were from central China. The results indicate that accessions from Japan are distinct from Chinese ones, and Japanese accessions had more close relationship with Chinese northeast spring and southern spring ecotypes. We further analyzed five agronomic trait-related SSR loci and found that the preponderant alleles are different in Chinese and Japanese soybean. Our study provides important insights into further utilization of Japanese soybean in Chinese soybean breeding.     

Assessment of genetic diversity among African cassava Manihot esculenta Grantz accessions resistant to the cassava mosaic virus disease using SSR markers

A study was conducted to determine the extent of genetic diversity among African cassava (Manihot esculenta Crantz) accessions resistant to the cassava mosaic virus disease (CMD), using simple sequence repeat (SSR) markers. The accessions included a breeding stock (clone 58308), five improved lines, 62 CMD resistant and 10 CMD susceptible landraces. Genetic diversity was assessed among accessions in five cluster groups derived from UPGMA analysis on data from 18 SSR primer pairs. Average gene diversity, He, was high in all cluster groups, with an average heterozygosity of 0.591 ± 0.061. The estimator of inbreeding Fis revealed a low level of inbreeding within groups and averaged −0.262 ± 0.142. Gene diversity among all accessions was 51.4% and gene diversity within cluster groups was 46.6%, while 4.8% was due to diversity between the different cluster groups. The amount of genetic differentiation measured by Gst and Fst were 9.6% and 12.1% respectively, indicating a weak genetic structure.     

Genetic structure and history of Swiss maize (<Emphasis Type="Italic">Zea mays</Emphasis> L. ssp. <Emphasis Type="Italic">mays</Emphasis>) landraces

Between 1930 and 2003 with emphasis on the 1940s maize landraces (Zea mays L. ssp. mays) from all over Switzerland were collected for maintenance and further use in a new Swiss breeding program. The genetic relationship and diversity among these accessions stored in the Swiss gene bank is largely unknown. Our hypothesis was that due to the unique geographic, climatic, and cultural diversity in Switzerland a diverse population of maize landraces had developed over the past three centuries. The aims were to characterize the genetic diversity of the Swiss landraces and their genetic relationship with accessions from neighbouring regions as well as reviewing their history, collection, and maintenance. The characterization and grouping was based on analyses with ten microsatellite markers. Geographic, cultural, and climatic conditions explained a division in two distinct groups of accessions. One group consisted of landraces collected in the southern parts of Switzerland. This group was related to the Italian Orange Flints. The other group contained accessions from northern Switzerland which were related to Northern European Flints in particular German Flints. Historic evidence was found for a frequent exchange of landraces within the country resulting in a lack of region-specific or landrace-specific genetic groups. The relatively large separation between the accessions, indicated by high F _ST (0.42), might be explained partly by a bottleneck during the collection and maintenance phase as well as by geographical and cultural separation of north and south of the country. Due to the high genetic diversity, the accessions here are a potential resource for broadening the European flint pool.     

Genetic diversity and relationships among safflower (<Emphasis Type="Italic">Carthamus tinctorius</Emphasis> L.) analyzed by inter-simple sequence repeats (ISSRs)

Genetic diversity and relationships among 48 safflower accessions were evaluated using 22 inter-simple sequence repeats (ISSR) primers. A total of 429 bands were amplified, and 355 bands (about 82.7%) were polymorphic. Five to forty-one polymorphic bands could be amplified by each primer, with an average of 16.1 polymorphic bands per primer. The results showed that the polymorphism of the safflower germplasm was higher at the DNA level. All the 48 accessions could be distinguished by ISSR markers and were divided into 9 groups based on ISSR GS by using UPGMA method. The genetic relationships among the accessions from different continents were closer. Comparatively, the genetic diversity of the accessions originated from Asia was higher, from Europe assembled. The results also showed that the genetic variation of accessions from Indian and Middle Eastern safflower diversity centers were relatively higher. ISSR is an effective and promising marker system for detecting genetic diversity among safflower and give some useful information on its phylogenic relationships.     

Genetic diversity in Nordic horseradish,Armoracia rusticana,as revealed by AFLP markers

176 horseradish accessions from the Nordic countries Denmark, Finland, Norway and Sweden were analysed to estimate the level of genetic diversity and to propose conservation strategies for this cultivated plant. Most of the accessions were collected in old gardens of the Nordic countries but selections from European countries and Danish breeding lines were also included in the study. Since horseradish is mainly vegetative propagated the genetic diversity has been assumed to be small. However, using the AFLP method with three primer combinations we revealed a significant genetic diversity among Nordic horseradish. The analysis yielded 65 polymorphic bands and we found an overall diversity index of 0.5 (Shannon–Weaver). The highest diversity was found among the Finnish accessions followed by the Danish accessions. An overall AMOVA analysis indicated that 90 % of the variation could be explained by among accession variation. The AFLP data assigned the different accessions into groups that corresponded with their country of origin. A closer relationship was observed between the Swedish, Danish and some of the Norwegian accessions while the Finnish accessions separated more clearly from the other three countries. A possible explanation for the diversity is that horseradish probably has been introduced to the Nordic countries at many occasions during a long period of time.     

Genetic differentiation of watermelon landrace types in Mali revealed by microsatellite (SSR) markers

This study describes the genetic differentiation of a collection of 134 watermelon landrace accessions from Mali, representing red fleshed dessert and white fleshed seed and cooking type watermelons from five regions, plus three commercial dessert type cultivars with red flesh. The material was represented by in total 397 plants and was analysed using 24 microsatellite primer sets, which differentiated 129 alleles across all loci. Analyses of molecular variance ascribed 51 % of the variation among the landrace accessions, and 14 % of the variation could be ascribed to the regions. Partitioning the accessions into use groups (dessert, cooking, seed processing) explained 25 % of the variation. When categorising the accessions further into 10 landrace types, differentiated on the basis of use groups, local accession name, flesh colour and seed phenotype, these landrace types explained 26 % of the variation. Analysis with the software Structure revealed that the accessions with confidence could be separated into two major genetic groups, related to flesh colour (red and white) of the watermelon fruits. The same analysis further indicated that the material may be differentiated into eight genetic sub-groups. One group included again the red fleshed dessert types with local and commercial origin, while the remaining seven genetic sub-groups comprised the white fleshed landrace types used for seed processing and cooking, as well as white fleshed types of one dessert type. Some of the seed and cooking types were to a large extent different and assigned to one genetic sub-group each. A Mantel test, based on geographical and genetic distance matrices showed a positive correlation, indicating that seed exchange has not overcome local adaptation.     

Preliminary study of genetic diversity in Swedish flax (Linum usitatissimum)

To investigate the genetic diversity of Linum usitatissimumL. in Sweden, 18 accessions, including 13 cultivars and five landraces, were analysed. This study was based on genetic variation in three enzyme systems (i.e., PGD, GPI and MDH) by using horizontal starch gel electrophoresis. The total genetic diversity of the studied flax material was very high (H _T= 0.62). Even though the highest genetic diversity lies within the accessions (G _ST= 0.07), a clear differentiation between fibre and oil flax was found with respect to three polymorphic loci (Pgd-1, Gpi-2 and Mdh-1). A phenogram, based on Nei's genetic distances between the accessions studied, showed five clearly defined groups but with low variation within the groups. The unexpected high genetic diversity found within accessions in the studied flax material may indicate that flax is more outbreeding than earlier believed.     

Molecular characterization of mulberry genetic resources indigenous to India

Mulberry (Morus L.) is essential for the sericulture industry as the primary feed for the silkworm Bombyx mori L. in India, with its long tradition of practicing sericulture, has a large number of indigenous cultivars. Since knowledge on the genetic divergence of these cultivars/varieties is essential for proper conservation and utilization, Inter Simple Sequence Repeat (ISSR) profiling was employed to assess genetic relationships among 34 mulberry accessions, collected from different regions of India. By using 12 ISSR primers, which produced 72 markers displaying a high degree of polymorphism (94.4%), genetic dissimilarity coefficients were calculated for each pair of the accessions and clustering of the accessions with Unweighted Pair Group Method using Arithmetic average (UPGMA) analysis was done to unravel the genetic diversity among the accessions. The dissimilarity coefficients varied from 0.111 to 0.692. UPGMA analysis generated a dendrogram with six groups and five isolates. Clustering of the accessions did not correspond with the information on the geographic origin of many of the accessions. Two-dimensional representations of the relative positions of the accessions with regards to divergence using the first two canonical variates as co-ordinate axes revealed considerable variability among the cases in each group. Further, Discriminant Function Analysis (DFA) showed changes in the geographic origin of 11 accessions and species status of 20 accessions.     

Genetic Diversity among the Germplasm Resources of the Genus <Emphasis Type="Italic">Houttuynia</Emphasis> Thunb. in China based on RAMP Markers

The genetic diversity of 70 Houttuynia Thunb. accessions from Sichuan, Chongqing, Guizhou and Jiangsu province in China were tested by using random amplified microsatellite polymorphism (RAMP) markers. All of the 43 primer combinations were found to amplify polymorphic products. A total of 304 products were amplified. Of which, 97.7 products were polymorphic. 6.9 polymorphic bands were amplified by each primer combination on average. The genetic similarity (GS) between the accessions within H. emeiensis and H. cordata were 0.660 and 0.575, respectively. The GS between two species was 0.525. The GS values between H. emeiensis and the H. cordata cytotype with the chromosome number of 36 was 0.559, higher than that between H. emeiensis and the cytotypes of H. cordata with other chromosome numbers. Within the species H. cordata, the genetic variation between cultivated and wild accessions was insignificant. The results of cluster analysis by using UPGMA method showed that all the tested accessions could be differentiated by RAMP markers, and classified into 11 groups. Many accessions with the same chromosome numbers could be classified together. The genetic diversity was more plentiful in mountainous and margin areas of the Sichuan Basin than at the bottom of the Basin and the highlands or hills surrounding it. It was concluded that there existed higher genetic diversity at the molecular level (RAMP markers) among the germplasm resources of the genus Houttuynia. The genetic relationships and phylogeny of the germplasm resources of Houttuynia were also discussed.     

Genetic diversity of <Emphasis Type="Italic">Nelumbo</Emphasis> accessions revealed by RAPD

Total 65 lotus accessions in genus Nelumbo mainly collected from China, were subjected to random amplified polymorphic DNA (RAPD) markers to estimate the genetic diversity and to test the genetic basis of the relationships between morphotypes and molecular markers. Seventeen primers generated a total of 195 highly reproducible and discernible loci, among which 173 were polymorphic. Percent polymorphism varied from 66.7 to 100 with an average of 88.72, and five primers out of them, OPC05, OPG10, OPN20, OPP09 and OPS17, showed 100% polymorphism. A relatively high genetic diversity was detected among all the samples with the similarity coefficient values ranging from 0.45 to 0.85, and Nei’s gene diversity (h) 0.30, and Shannon index (I) 0.46. The UPGMA dendrogram clustered 65 accessions in four clusters and the clustering pattern showed two groups, N. nucifera ssp. nucifera and those accessions related to the American lotus, and some special cultivars, landraces, hybrids and the American lotus. Principal Coordinate Analysis (PCA) further indicated that the genetic diversity of Nelumbo accessions was not evenly distributed, instead, was presented by a clustered distribution pattern. Similar to the results revealed by the dendrogram, two main groups representing the two subspecies of N. nucifera, as well as some special landraces, cultivars of Chinese lotus, the Japanese lotus and hybrids out of the two groups were obtained. Neither the UPGMA dendrogram nor the PCA analysis exhibited strict relationship with geographic distribution and morphotypes among the accessions.     

The genetic characterization of Turkish watermelon (<Emphasis Type="Italic">Citrullus lanatus</Emphasis>) accessions using RAPD markers

Genetic diversity of the Turkish watermelon genetic resources was evaluated using different Citrullus species, wild relatives, foreign landraces, open pollinated (OP) and commercial hybrid cultivars by RAPD markers. The germplasm was consisted of 303 accessions collected from various geographical regions. Twenty-two of 35 RAPD primers generated a total of 241 reproducible bands, 146 (60.6%) of which were polymorphic. Based on the RAPD data the genetic similarity coefficients were calculated and the dendrogram was constructed using UPGMA (Unweighted pair-group method with arithmetic average). Cluster analysis of the 303 accessions employing RAPD data resulted in a multi-branched dendrogram indicating that most of the Turkish accessions belonging to var. lanatus of Citrullus lanatus (Thunb.) Matsum et Nakai were grouped together. Accessions of different Citrullus species and Praecitrullus fistulosus (Stocks) Pangalo formed distant clusters from C. lanatus var. lanatus. Among 303 accessions, a subset of 56 accessions was selected representing different groups and a second dendrogram was constructed. The genetic similarity coefficients (GS) within the Turkish accessions were ranged from 0.76 to 1.00 with 0.94 average indicating that they are closely related. Taken together, our results indicated that low genetic variability exist among the watermelon genetic resources collected from Turkey contrary to their remarkable phenotypic diversity.     

Genetic diversity in melon (Cucumis melo L.): Anevaluation of African germplasm

The genetic diversity among 126 exotic (108) andreference array (RA) melon (Cucumismelo L.) accessions (18) was assessed byvariation at 49 random amplified polymorphic DNA marker bands(putative loci) using 29 10-mer primers. Africanaccessions of unknown melon market classes were compared to the RAaccessions from a broad range of C.melo subsp. melo groups(Cantalupensis, Conomon, Inodorus and Flexuosus). Althoughdifferences in groupings occurred after multidimensional scaling andcluster analysis, both analyses placed African accessions into twogroups, which were separate from RA groupings. One African group of33 accessions containing accessions from Zimbabwe (5),Zambia (24), Mali (1), one of two Senegalaccessions and two of three South African accessions examined. Thesecond group, which consisted of 67 accessions containing collectionsfrom Egypt (40), Tunisia (6), Libya(13), Morocco (1), Algeria (2),Ethiopia (1), Niger (1), Sierra Leone(1), S. Africa (1), Zambia (1) andZimbabwe (1). Depending on the multivariate analysistechnique employed, accessions from Kenya, Senegal and Ghana formedeither unique groupings or were grouped with accessions(Cantalupensis) from the RA. Both analyses indicate thatthe genetic differences inherent between the African gene pools isassociated with the geographic proximity of African countries(northern vs. central-southern Africa) in thegermplasm array examined. Moreover, these data indicate that thegenetic diversity of U.S. and European commercial RA germplasm(Cantalupensis and Inodorus) could be enhanced by theintroduction of genetic variation from African accessions, and thatit would be advantageous to acquire more accessions from thisgeographically and ecologically varied region to ensure the retentionof existing genetic diversity.     

The use of characterisation data to establish the Indian mungbean core collection and assessment of genetic diversity

A representative core set of well characterised Indian mungbean collection was developed using information on passport, characterisation and evaluation data. Initial diversity groups of the accessions comprising the whole collection were formed based on six major crop growing zones and a separate group for a few accessions from diverse exotic sources. Principal components score strategy was found to be most useful in maximising the selection inertia than strictly random sampling in all individual groups. A total of 152 accessions were extracted and the validity of their representativeness was established by comparing its diversity with that of the whole collection. Shannon diversity index for qualitative characters and certain statistical parameters for quantitative variables were used for measuring the diversity of the accessions in the core set and that of the whole collection. The representative core set was subjected to multivariate analysis for assessment of genetic diversity and also the variation patterns for discriminating among accessions to facilitate the users for easy accessibility, and effective and efficient utilisation of the material.     

Characterization of American hazelnut (Corylus americana) accessions and Corylus americana?×?Corylus avellana hybrids using microsatellite markers

The American hazelnut (Corylus americana Marshall) is native to the eastern United States and Southern Canada. In the early decades of the last century, breeding work by several individuals attempted to combine the cold hardiness and disease resistance of the American hazelnut with the larger nut size of the European hazelnut (C. avellana L.). Many hybrid selections grown today trace back to these early efforts. Over the past three decades, representatives of C. americana were collected and are preserved in Corvallis, Oregon. Seeds were collected along roadsides, in hedgerows, in woodland clearings, and in gardens. The seeds were germinated and the best of the resulting seedlings were preserved for later use. In this study, genetic diversity was studied in 87 American and 67 hybrid hazelnut selections using 21 microsatellite loci. The total number of alleles was 266 in the 162 accessions examined, of which 229 were present in C. americana accessions, but only 168 in the Arbor Day Farm hybrids, and 116 in the hybrids of C. americana ‘Rush’. In the American accessions, a high level of genetic diversity was observed (H _e ?=?0.74, H _o ?=?0.68). A genetic similarity matrix of the American and hybrid accessions, and a few European cultivars, was constructed and the resulting dendrogram revealed seven major groups: European cultivars and ‘Rush’ hybrids, two groups of Arbor Day Farm hybrids, three groups of C. americana accessions, and a mixed group of hybrid and American accessions. Analysis confirmed the reported parentage of 10 hybrids. The genetic diversity among the American hazelnut accessions, untapped to date, will be useful in breeding hybrids that will allow expansion of hazelnut production into eastern North America.