Summer Squash Identification by High-Resolution-Melting (HRM) Analysis Using Gene-Based EST–SSR Molecular Markers

Cucurbita pepo (squash, pumpkin, gourd), a worldwide cultivated vegetable of American origin, is extremely variable in fruit characteristics. Most of its widely grown commercial types are known as summer squashes and belong to the elongated forms of C. pepo ssp. pepo (Cocozelle, Vegetable marrow and Zucchini groups). Here, we have integrated the high-resolution-melting (HRM) analysis method with expressed sequence tags–simple sequence repeat (EST–SSR) marker genotyping, in order to facilitate the identification of 36 summer squash landraces originated from Greece. The six EST–SSR loci used were informative and generated a unique melting curve profile of EST-derived microsatellites for each accession allowing their comparison and classification. Moreover, HRM was highly informative, as by using only four microsatellite markers we were able to discriminate 36 summer squash landraces and by using six EST–SSRs. We were able to construct a highly informative and discriminative dendrogram where the 36 genotypes were classified in six distinct clusters. Furthermore, we acquired information about the genes containing the EST–SSRs using bioinformatics tools. We found that the EST–SSRs used in this study were hybridizing to genes involved in stress response to heavy metals and biotic stresses or the production of flavonoids or symporters of important nitrogen sources, like xanthine and uric acid amongst others. The results presented here suggest that the panel of EST–SSR markers used in combination with HRM analysis could be useful in a variety of applications, like squash biodiversity assessment but most importantly in managing squash germplasm to improve breeding programs.     

Genetic Analysis of Indian Lentil (Lens culinaris Medikus) Cultivars and Landraces Using RAPD and STMS Markers

Molecular analysis of 29 lentil (Lens culinaris) cultivars and landraces of Indian origin was carried out using twenty RAPD and ten cross-species STMS primers. A total of 97 markers (72 RAPD and 25 STMS) were amplified of which 42.3% were polymorphic. Genetic similarity among the cultivars and landraces was 89.7%. The observed results indicated low level of genetic diversity in the studied material. UPGMA cluster analysis for the combined data of RAPD and STMS revealed two broad clusters — Cluster I with three landraces and Cluster II containing all remaining landraces and cultivars except Precoz. Germplasm line Precoz was found to be the most distinct in individual as well as combined analyses. All cultivars and landraces except K-75 and L4076 could be discriminated from one another using combined data for the two techniques. Germplasm lines Precoz, L830 and cultivars L4147 and JL3 were quite distinct and could be potential germplasm resource.     

Evaluation of Genetic Diversity of Chilli Landraces from North Eastern India Based on Morphology, SSR Markers and the Pun1 Locus

The chilli (Capsicum sp.) germplasm found throughout North Eastern (NE) India exhibits wide variability in fruit morphology, pungency, bearing habit and crop duration. As the genetic resources of chilli landraces from this region are not well documented, it is likely that they have hitherto unknown alleles and/or genes for economically important traits. In this study, 53 chilli accessions from different areas of this NE region were evaluated for genetic diversity using various morphological characters and 50 simple sequence repeat markers. It was found that erect and campanulate fruit types are grouped in separate clusters. The number of alleles per locus ranged from 3 to 9 with an average of 5.36. The average polymorphic information content value was 0.52. Percentage variation among populations, within individuals of population and within individuals was found to be 34, 57.9 and 8.05 %, respectively, indicating diversity in the landraces sampled. Allele mining across acyltransferase 3 (AT3) gene in a set of landraces led to identification of new single nucleotide polymorphisms (SNPs). Sequence analysis of the 2,349 bp AT3 region revealed the presence of a total of 79 SNPs and 3 indels. This overview of diversity of chilli landraces from NE India paves the way for conservation and utilisation of germplasm and contributes to the development of systematic breeding strategies.     

Genetic diversity of cultivated flax (Linum usitatissimum L.) germplasm assessed by retrotransposon-based markers

Retrotransposon segments were characterized and inter-retrotransposon amplified polymorphism (IRAP) markers developed for cultivated flax (Linum usitatissimum L.) and the Linum genus. Over 75 distinct long terminal repeat retrotransposon segments were cloned, the first set for Linum, and specific primers designed for them. IRAP was then used to evaluate genetic diversity among 708 accessions of cultivated flax comprising 143 landraces, 387 varieties, and 178 breeding lines. These included both traditional and modern, oil (86), fiber (351), and combined-use (271) accessions, originating from 36 countries, and 10 wild Linum species. The set of 10 most polymorphic primers yielded 141 reproducible informative data points per accession, with 52% polymorphism and a 0.34 Shannon diversity index. The maximal genetic diversity was detected among wild Linum species (100% IRAP polymorphism and 0.57 Jaccard similarity), while diversity within cultivated germplasm decreased from landraces (58%, 0.63) to breeding lines (48%, 0.85) and cultivars (50%, 0.81). Application of Bayesian methods for clustering resulted in the robust identification of 20 clusters of accessions, which were unstratified according to origin or user type. This indicates an overlap in genetic diversity despite disruptive selection for fiber versus oil types. Nevertheless, eight clusters contained high proportions (70?C100%) of commercial cultivars, whereas two clusters were rich (60%) in landraces. These findings provide a basis for better flax germplasm management, core collection establishment, and exploration of diversity in breeding, as well as for exploration of the role of retrotransposons in flax genome dynamics.     

Genetic diversity and geographical differentiation of Iranian landrace,cultivars, and exotic chickpea lines as revealed by morphological and microsatellite markers

Assessment of the extent of genetic variability within chickpea is fundamental for chickpea breeding and conservation of genetic resources and is particularly useful as a general guide in the choice of parents for breeding hybrids. To establish genetic diversity among 60 accessions of chickpea comprising landraces, internationally developed improved lines, and cultivars, genetic distances were evaluated using 14 simple sequence repeat markers. These markers showed a high level of polymorphism; a total of 59 different alleles were detected, with a mean of 4.2 alleles per locus. The polymorphic information content (PIC) value ranged from 0.31 to 0.89. All the markers, with the exception of TAA170, TA110, GA34, and Ts35, were considered to be informative (PIC > 0.5), indicating their potential usefulness for cultivar identification. Based on the UNJ clustering method, all accessions were clustered in five groups, which indicated the probable origin and region similarity of Iranian landraces over the other cultivars. It also represents a wide diversity among available germplasm. The result has firmly established that introduction of genetic materials from exotic sources has broadened the genetic base of the national chickpea breeding program. As further implications of the findings, this study can be useful for selective breeding for specific traits and in enhancing the genetic base of breeding programs.     

Genetic diversity in Capsicum germplasm based on microsatellite and random amplified microsatellite polymorphism markers

A sound knowledge of the genetic diversity among germplasm is vital for strategic germplasm collection, maintenance, conservation and utilisation. Genomic simple sequence repeats (SSRs) and random amplified microsatellite polymorphism (RAMPO) markers were used to analyse diversity and relationships among 48 pepper (Capsicum spp.) genotypes originating from nine countries. These genotypes covered 4 species including 13 germplasm accessions, 30 improved lines of 4 domesticated species and 5 landraces derived from natural interspecific crosses. Out of 106 SSR markers, 25 polymorphic SSR markers (24 %) detected a total of 76 alleles (average, 3.04; range, 2–5). The average polymorphic information content (PIC) was 0.69 (range, 0.29–0.92). Seventeen RAMPO markers produced 87 polymorphic fragments with average PIC of 0.63 (range, 0.44–0.81). Dendrograms based on SSRs and RAMPOs generated two clusters. All 38 Capsicum annuum genotypes and an interspecific landrace clustered together, whereas nine non-annuum (three Capsicum frutescens, one Capsicum chinense, one Capsicum baccatum and four interspecific landraces) genotypes clustered separately. Genetic variation within non-annuum genotypes was greater than the C. annuum genotypes. Distinctness of interspecific derivative landraces grown in northeast India was validated; natural crossing between sympatric Capsicum species has been proposed as the mechanism of their origin.     

Molecular Differentiation of Sexually Incompatible Strains of Agaricus bitorquis Using RAPD and AFLP Markers

Twenty RAPD primers amplified 216 DNA fragments in nine germplasm strains and two newly developed hybrids of Agaricus bitorquis, out of which 98.61% were polymorphic. Six AFLP primer-combinations generated a total of 271 AFLP fragments in nine germplasm strains and six newly developed hybrids, out of which 91.14% were polymorphic. Dendrograms based on UPGMA algorithm and SAHN clustering clearly showed two major phylogenetic groups with both the DNA markers in the germplasm and the hybrids clustered with their parental groups. Genetic similarity between the two groups was 6.52% with RAPD and 18.13% with AFLP markers. Ten most informative primers were identified for initial screening of uncharacterized germplasm using RAPD analysis. Further, AFLP revealed a great power of detection of genetic diversity and validated its usefulness for guiding breeding programmes. The findings are of immediate value to breeders to explore hybridization between genetically diverse parents within the sexually compatible groups. Present study is the first report on the exploitation of AFLP markers in button mushroom for molecular characterization and mushroom breeding.     

Swiss Mattenklee landraces,a distinct and diverse genetic resource of red clover (<Emphasis Type="Italic">Trifolium pratense</Emphasis> L.)

Genetic variability within and among 19 landraces and cultivars of red clover ( Trifolium pratense L.) was investigated by means of amplified fragment length polymorphism (AFLP) analysis in order to assess the potential value of Swiss Mattenklee landraces as genetic resources for plant breeding and the preservation of biodiversity. Populations were classified into three groups according to their origin and agronomic features: Mattenklee landraces (8), Mattenklee cultivars (8) and field clover cultivars (3). Analysis of molecular variance based on 276 polymorphic AFLP markers revealed 80% of total variability to be due to variability within populations while 12% were attributed to variability among groups. Stepwise discriminant analysis identified a subset of 126 AFLP markers which best separated individual plants into the three respective groups. Genetic distances between populations were considerably larger among groups than among populations within the same group, providing further evidence for the genetic distinction between Mattenklee landraces, Mattenklee cultivars and field clover cultivars. AFLP markers identified two landrace clusters, containing three and four populations respectively, which, together with one additional landrace, may sufficiently represent the genetic variability of all eight landraces investigated. The results of this study strongly suggest that Swiss Mattenklee landraces form a genetically distinct group of red clover. The data obtained provide criteria on how to efficiently manage, preserve and exploit Mattenklee germplasm.     

Genetic diversity and population structure of common bean (Phaseolus vulgaris) landraces from China revealed by a new set of EST-SSR markers

A new set of EST-SSR markers were developed and employed to analyze the genetic diversity and population structure of Phaseolus vulgaris in China. A total of 2452 microsatellites were identified in 2144 unigenes assembled from P. vulgaris ESTs, indicating that merely 6.9% of the 30,952 unigene sequences contained SSRs. Seventeen of 153 randomly designed EST-SSR primer pairs successfully amplified polymorphic products in 31 landraces from six major production provinces of China, with the mean number of alleles per locus of 2.700 and polymorphism information content of 0.378. The observed and expected heterozygosity ranged from 0.100 to 0.954 and 0.081 to 0.558, respectively. Using these markers, both an unrooted neighbor-joining tree and principal coordinates analysis showed that almost all of the landraces were separated according with their regional distribution. Moreover, population structure analysis revealed that all genotypes formed into three distinct clusters (k = 3), suggesting that geographic and climatic factors could provide diverse degrees of selection pressure. Accordingly, germplasm collection and cross breeding among different regions are suggested to accelerate the process of diverse germplasm creation and broaden germplasm resources of Chinese common bean.     

利用RAPD和ISSR分子标记分析怀地黄种质遗传多样性

用RAPD与ISSR技术对怀地黄的8个品种和2个脱毒品系进行了种质遗传多样性分析。分别从80条RAPD引物和44条ISSR引物中筛选出适合怀地黄种质分析的17条RAPD引物和10条ISSR引物,用于RAPD和ISSR分析。17条RAPD引物共扩增出177条带, 多态性位点数为109; 多态性位点比率为61.58%;平均多样性指数(I)为0.3135;每个位点的有效等位基因数（Ne）是1.3641; 10条ISSR引物共扩增出110条带. 多态性位点数为79; 多态性位点比率为71.58%;平均多样性指数(I)为0.3577;每个位点的有效等位基因数（Ne）是1.4037。 基于扩增条带数据库建立了各自的Jaccard遗传相关系数矩阵,构建了相似的分子树状图,将10个供试材料分为2类:一类群含组培85.5、大田85.5、组培9302、大田9302、金状元和金白6个材料;另一类群含北京1号、大红袍、地黄9104和野生地黄4个材料。两种分子标记的分析结果呈极显著正相关(r＝0.649)。结果表明,RAPD与ISSR标记适合于怀地黄种质遗传多样性分析,ISSR标记技术是一种多态性和重复性优于RAPD技术的实用技术。     

Comparative analysis of phenotypic and genotypic diversity among plantain landraces (Musa spp., AAB group)

Genetic diversity amongst 76 plantain landraces has been studied using RAPD analysis at two levels of intensity and compared with groupings based on phenotypic indices and morphotype. There was a good correlation (R²=0.78) between estimates of genetic diversity based on 76 RAPD bands and 164 RAPD bands. However, there was a poor correlation between RAPD-based estimates of genetic diversity and a phenotypic index based on agronomic characters. There was also a poor correlation between RAPD analyses and morphotype group (based on bunch type and stature). These results suggest that the traditional designations of plantain landraces based on morphotype do not provide a true reflection of overall genetic divergence. Similarly, classification systems using phenotypic indices based on agronomic characters may not provide accurate taxonomic differentiation. The level of genetic divergence within morphogroups based on bunch type suggests that True Horn plantains are derived from False Horn plantains which in turn are derived from French plantains. Genetic divergence was found to be generally quite low within the plantain landrace genepool, which is consistent with the proposed evolution of this germplasm through somatic mutation of a relatively small number of introductions. However, putative synonyms/duplicates have been shown to be genetically distinct. In contrast, a group of 12 landraces have been identified that are highly distinct from one another (showing 20–35% dissimilarity). Fertile members of this group may be useful for generating genetically diverse 2x and 4x breeding populations that can be used in breeding secondary triploid hybrid plantain varieties. Received: 8 January 2000 / Accepted: 2 March 2000     

DNA based iPBS-retrotransposon markers for investigating the population structure of pea (Pisum sativum) germplasm from Turkey

Retrotransposons have been highly studied in monocots; however retrotransposon diversity in dicot crops has not been well documented. Our objective was to assess the diversity harbored by field pea landraces using retrotranposon markers. In this research, molecular characterization of 104 landraces and 34 field pea breeding lines was assessed using newly developed iPBS-retrotransposon markers. The 12 iPBS-retrotransposon primers generated a total 106 scorable bands, and 81 of these were found to be polymorphic (76.4%), with an average of 6.75 polymorphic fragments per primer. Polymorphism information content (PIC) ranged from 0.33 to 0.84 with an average of 0.61. It was evident that field pea landraces from the same geographical region were often placed in different groups in the neighbor joining analysis, indicating that grouping based on genetic parameters was not closely related to the geographical origin. The population structure was determined by using STRUCTURE software, and three populations at K = 3 and five populations at K = 5 were identified among landraces. The plentiful diversity present in Turkish field pea landraces could be used as genetic resource in designing breeding program, and may also contribute to worldwide pea breeding programs. Our data also suggested a role of iPBS-retrotransposons as ‘a universal marker’ for molecular characterization of pea germplasm.     

Unlocking the Genetic Diversity of Maize Landraces with Doubled Haploids Opens New Avenues for Breeding

Landraces are valuable genetic resources for broadening the genetic base of elite germplasm in maize. Extensive exploitation of landraces has been hampered by their genetic heterogeneity and heavy genetic load. These limitations may be overcome by the in-vivo doubled haploid (DH) technique. A set of 132 DH lines derived from three European landraces and 106 elite flint (EF) lines were genotyped for 56,110 single nucleotide polymorphism (SNP) markers and evaluated in field trials at five locations in Germany in 2010 for several agronomic traits. In addition, the landraces were compared with synthetic populations produced by intermating DH lines derived from the respective landrace. Our objectives were to (1) evaluate the phenotypic and molecular diversity captured within DH lines derived from European landraces, (2) assess the breeding potential (usefulness) of DH lines derived from landraces to broaden the genetic base of the EF germplasm, and (3) compare the performance of each landrace with the synthetic population produced from the respective DH lines. Large genotypic variances among DH lines derived from landraces allowed the identification of DH lines with grain yields comparable to those of EF lines. Selected DH lines may thus be introgressed into elite germplasm without impairing its yield level. Large genetic distances of the DH lines to the EF lines demonstrated the potential of DH lines derived from landraces to broaden the genetic base of the EF germplasm. The comparison of landraces with their respective synthetic population showed no yield improvement and no reduction of phenotypic diversity. Owing to the low population structure and rapid decrease of linkage disequilibrium within populations of DH lines derived from landraces, these would be an ideal tool for association mapping. Altogether, the DH technology opens new opportunities for characterizing and utilizing the genetic diversity present in gene bank accessions of maize.     

Determination of genetic relationships among shape Phaseolus vulgaris populations in a conical cross from RAPD marker analyses

Random-amplified polymorphic DNA (RAPD) markers were used to determine genetic relationships among Phaseolus vulgaris breeding populations. Genetic distances were calculated from the distribution of 317 RAPD markers among 8 parents, 10 individuals from 8 cycle-one populations, 10 individuals from 6 cycle-two populations and 10 individuals from 2 cycle-three populations of a conical cross. Genetic distances between populations and parents were consistent with their degree of relationship in the crossing scheme indicating that a RAPD analysis is a sensitive and useful method for categorizing breeding materials according to their genetic similarities. Genetic variation among individuals within populations increased from cycle one to cycle three and variation among populations within the cycles decreased from cycle one to cycle three in the conical cross. The results showed that this crossing scheme can be used to collect the genetic diversity in eight parents into a single plant breeding population. Abbreviations: CBB, common bacterial blight; GD, genetic distance; RAPD, random-amplified polymorphic DNA     

Identification and analysis of genetic variation among rose cultivars using random amplified polymorphic DNA

Identified germplasm is an important component for efficient and effective management of plant genetic resources. Traditionally, cultivars or species identification has relied on morphological characters like growth habit or floral morphology like flower colour and other characteristics of the plant. Studies were undertaken for identification and analysis of genetic variation within 34 rose cultivars through random amplified polymorphic DNA (RAPD) markers. Analysis was made by using twenty five decamer primers. Out of twenty five, ten primers were selected and used for identification and analysis of genetic relationships among 34 rose cultivars. A total of 162 distinct DNA fragments ranging from 0.1 to 3.4 kb was amplified by using 10 selected random decamer primers. The genetic similarity was evaluated on the basis of presence or absence of bands. The cluster analysis indicated that the 34 rose cultivars form 9 clusters. The first cluster consists of eight hybrid cultivars, three clusters having five cultivars each, one cluster having four cultivars, two clusters having three cultivars each and two clusters having one cultivar each. The genetic distance was very close within the cultivars. Thus, these RAPD markers have the potential for identification of clusters and characterization of genetic variation within the cultivars. This is also helpful in rose breeding programs and provides a major input into conservation biology.     

Determination of genetic diversity among Saccharina germplasm using ISSR and RAPD markers

Various species of genus Saccharina are economically important brown macroalgae cultivated in China. The genetic background of the conserved Saccharina germplasm was not clear. In this report, DNA-based molecular markers such as inter simple sequence repeats (ISSR) and random amplified polymorphic DNA (RAPD) were used to assess the genetic diversity and phylogenetic relationships among 48 Saccharina germplasms. A total of 50 ISSR and 50 RAPD primers were tested, of which only 33 polymorphic primers (17 ISSR and 16 RAPD) had an amplified clear and reproducible profile, and could be used. Seventeen ISSR primers yielded a total of 262 bands, of which 256 were polymorphic, and 15.06 polymorphic bands per primer were amplified from 48 kelp gametophytes. Sixteen RAPD primers produced 355 bands, of which 352 were polymorphic, and 22 polymorphic bands per primer were observed across 48 individuals. The simple matching coefficient of ISSR, RAPD and pooled ISSR and RAPD dendrograms ranged from 0.568 to 0.885, 0.670 to 0.873, and 0.667 to 0.862, revealing high genetic diversity. Based on the unweighted pair group method with the arithmetic averaging algorithm (UPGMA) cluster analysis and the principal components analysis (PCA) of ISSR data, the 48 gametophytes were divided into three main groups. The Mantel test revealed a similar polymorphism distribution pattern between ISSR and RAPD markers, the correlation coefficient r was 0.62, and the results indicated that both ISSR and RAPD markers were effective to assess the selected gametophytes, while matrix correlation of the ISSR marker system (r = 0.78) was better than that of the RAPD marker system (r = 0.64). Genetic analysis data from this study were helpful in understanding the genetic relationships among the selected 17 kelp varieties (or lines) and provided guidance for molecular-assisted selection for parental gametophytes of hybrid kelp breeding.     

RAPD标记在紫菜遗传多样性检测和种质鉴定中的应用

用ＲＡＰＤ技术对４类紫菜（Ｐｏｒｐｈｙｒａ ｙｅｚｏｅｎｓｉｓ,Ｐ．ｈａｉｔａｎｅｎｓｉｓ,Ｐ．ｋａｔａｄｎｉ ｖａｒ．ｈｅｍｉｐｈｙｌｌａ和Ｐ．ｏｌｉｇｏｓｐｅｒｍａｔａｎｇｉａ）的１５个无性系丝状体进行了遗传多样履分析,从５０个ＯＰＥＲＯＮ引物中经过初筛,其中６个引物可以扩增出稳定的可重复的图谱。这６个引物共扩增出了６０条带,多态性比例达９７．１％。根据ＲＡＰＤ结果将这１５个无性了紫菜的ＤＮＡ     

Unraveling the efficiency of RAPD and SSR markers in diversity analysis and population structure estimation in common bean

Increase in food production viz-a-viz quality of food is important to feed the growing human population to attain food as well as nutritional security. The availability of diverse germplasm of any crop is an important genetic resource to mine the genes that may assist in attaining food as well as nutritional security. Here we used 15 RAPD and 23 SSR markers to elucidate diversity among 51 common bean genotypes mostly landraces collected from the Himalayan region of Jammu and Kashmir, India. We observed that both the markers are highly polymorphic. The discriminatory power of these markers was determined using various parameters like; percent polymorphism, PIC, resolving power and marker index. 15 RAPDs produced 171 polymorphic bands, while 23 SSRs produced 268 polymorphic bands. SSRs showed a higher PIC value (0.300) compared to RAPDs (0.243). Further the resolving power of SSRs was 5.241 compared to 3.86 for RAPDs. However, RAPDs showed a higher marker index (2.69) compared to SSRs (1.279) that may be attributed to their higher multiplex ratio. The dendrograms generated with hierarchical UPGMA cluster analysis grouped genotypes into two main clusters with various degrees of sub clustering within the cluster. Here we observed that both the marker systems showed comparable accuracy in grouping genotypes of common bean according to their area of cultivation. The model based STRUCTURE analysis using 15 RAPD and 23 SSR markers identified a population with 3 sub-populations which corresponds to distance based groupings. High level of genetic diversity was observed within the population. These findings have further implications in common bean breeding as well as conservation programs.     

The Application of RAPD Markers in Diversity Detection and Variety Identification of Porphyra

RAPD (random amplified polymorphic DNA) markers were generated from filaments of 15 Porphyra lines representing four important groups, P. yezoensis, P. haitanensis, P. katadai var. hemiphylla and P. oligospermatangia. Among the total 69 fragments generated by 6 selected primers (among 50 primers), 67 appeared to be polymorphic (97.1%). Cluster analysis based on the RAPD results was performed. The 15 Porphyra lines were divided into 3 groups. This result was consistent with that from taxonomy analysis. A DNA fingerprinting based on 8 bands amplified with OPN-02 and OPJ-18 was constructed and might be used in Porphyra variety identification. Five specific RAPD fragments of 5 Porphyra lines were isolated and cloned into pGEM-T easy vector. These five RAPD fragments may be useful in germplasm identification and property protection of Porphyra.     

Qualitative and quantitative characterization of RAPD variation among snap bean (Phaseolus vulgaris) genotypes

Ten snap bean (Phaseolus vulgaris) genotypes were screened for polymorphism with 400 RAPD (random amplified polymorphic DNA) primers. Polymorphic RAPDs were scored and classified into three categories based on ethidium bromide staining intensity. An average of 5.19 RAPD bands were scored per primer for the 364 primers that gave scorable amplification products. An average of 2.15 polymorphic RAPDs were detected per primer. The results show that primer screening may reduce the number of RAPD reactions required for the analysis of genetic relationships among snap-bean genotypes by over 60%. Based on the analysis of the distribution of RAPD amplification, the same number of polymorphic RAPDs were amplified from different genotypes for all RAPD band intensity levels. A comparison of RAPD band amplification frequency among genotypes for the three categories of bands classified by amplification strength revealed a measurable difference in the frequencies of RAPDs classified as faint (weakly amplifying) compared to RAPD bands classified as bold (strongly amplifying) indicating a possible scoring error due to the underscoring of faint bands. Correlation analysis showed that RAPD bands amplified by the same primer are not more closely correlated then RAPD bands amplified by different primers but are more highly correlated then expected by chance. Pairwise comparisons of RAPD bands indicate that the distribution of RAPD amplification among genotypes will be a useful criterion for establishing RAPD band identity. For the average pairwise comparison of genotypes, 50% of primers tested and 15.8% of all scored RAPDs detected polymorphism. Based on RAPD data Nei's average gene diversity at a locus was 0.158 based on all scorable RAPD bands and 0.388 if only polymorphic RAPD loci were considered. RAPD-derived 1 relationships among genotypes are reported for the ten genotypes included in this study. The data presented here demonstrate that many informative, polymorphic RAPDs can be found among snap bean cultivars. These RAPDs may be useful for the unique identification of bean varieties, the organization of bean germplasm, and applications of molecular markers to bean breeding.