Genetic characterization and identification of new accessions from Syria in an olive germplasm bank by means of RAPD markers

Thirty-two olive cultivar accessions from Syria, most of them obtained from collecting expeditions, were characterized by means of RAPD markers before being introduced in the World Germplasm Bank of Cordoba. A total of 79 polymorphic bands(6.1 polymorphisms per primer) out of 93(7.1 bands per primer) were scored for the13 primers used, corresponding to 84.9% of the amplification products. Thirty-one different genotypes were clearly discriminated. Differences were not found among the amplification profiles from different individuals of the same cultivar. Only two cases of mislabeling or errors of planting were found. Fourteen accessions corresponding to 6 homonyms were discriminated by RAPDs as different genotypes. The dendrogram obtained by RAPD analysis included three major groups. Some evidence of relationships of the Syrian accessions studied according to their geographic origin and/or diffusion was found. For instance, cultivars from the Central Syria (Tadmur/Palmyra)such as Toffahi', ‘Abbadi Abo Gabra’-1033,‘Abo Kanani’, ‘Shami’-1041, ‘Abbadi Shalal’ ‘Adgam’-844 and ‘Majhol’-1013 clustered in Group 1 and 2. Six cultivars from Northern Syria clustered in Group 2. But it was not found a geographic structure for the cultivars from South and West of Syria. These results agree with the hypothesis of autochthonous origin of most of the olive cultivars. Some associations between cultivars from Central Syria and their fruit size were observed. This suggests that fruit size was a criterion of local selection in olive cultivars of this area. This revised version was published online in July 2006 with corrections to the Cover Date.     

Assessing the genetic diversity of Portuguese maize germplasm using microsatellite markers

A collection of Portuguese maize accessions representing a valuable source of genes for introduction into modern cultivars is stored at the Portuguese Plant Germplasm Bank (Banco Português de Germoplasma Vegetal—BPGV). To assess genetic diversity among inbreds, microsatellite analysis was carried out for 54 inbred lines representing the diversity of Portuguese dent and flint maize germplasm. Fifty American and other European elite inbreds were also analysed for comparison. Fifteen microsatellite loci distributed throughout the maize genome were chosen based on their repeat unit and base composition. A total of 80 alleles were detected with an average allele number of 5.33 per locus. Polymorphism information content (PIC) values and observed genetic distances showed the existence of large variability among inbreds. Cluster analysis indicated that almost all of the inbreds could be distinguished from each other and Portuguese inbreds were present in all clusters formed. These associations were consistent with the known pedigree records of the inbreds, confirming a mixed origin of Portuguese materials. Comparative analysis of microsatellite diversity among groups was established according to important traits for both breeding and line identification. This revealed that, although most of the genetic diversity (>95%) was attributable to differences among inbreds of different groups, the existence of phenotypic differentiation in endosperm colour, kernel type and cob colour could be suggested for grouping. These findings support the joint use of molecular and morphological traits in management of the germplasm collection. In this study, SSR markers proved to be effective to characterise and identify maize inbred lines, and demonstrate associations among them. This revised version was published online in July 2006 with corrections to the Cover Date.     

Molecular characterization of genetic diversity in European germplasm of perennial ryegrass

Summary Perennial ryegrass (Lolium perenne L.) is the most important grass species for temperate grassland agriculture. The level and distribution of genetic variation in gene bank ecotype collections is still largely unknown but of great interest for the planning of breeding programs. The objectives of this study were to (i) assess the molecular diversity of Polish ecotypes of perennial ryegrass, and (ii) compare the relationship between this group and German ecotypes and European cultivars investigated previously. A total number of 166 polymorphic marker bands were detected among the 171 individual plants of the 9 Polish ecotypes. In a joint analysis with 9 Polish and 22 German ecotypes, and 22 European cultivars 172 polymorphic RAPD markers could be found. Genetic distance among the Polish ecotypes ranged from 0.31 to 0.51, while for all 53 populations a broader range was detected (0.25–0.67). An analysis of molecular variance (AMOVA) revealed a much larger variation within populations (71%) than among them (29%). The Polish ecotypes contained the highest within population variation (74%). The largest among group difference (15%) was found between the Polish ecotypes versus all other accessions. We conclude that the Polish ecotypes represent a valuable genetic resource for enlarging the genetic variation in the West European germplasm pool of perennial ryegrass.     

Assessment of genetic variability of olive varieties by microsatellite and AFLP markers

Fourteen developed microsatellite markers were characterized for their use in genotyping and diversity studies of olive varieties. After optimisation of microsatellite assay and allele sizing, ninety-six alleles were found in nineteen varieties, with an average of 6.8 alleles per locus. The characteristics of the microsatellite markers were used to identify markers that can be reliably applied for variety genotyping. Such features were the generation of complex banding patterns supported by underlying allele sequences, `short allele dominance', an unstable repeat structure and a low number of alleles. AFLP analysis was performed on the same set of olive varieties using eight primer pair combinations. The genetic relationships among nineteen olive varieties were compared on the basis of microsatellite and AFLP polymorphisms. Genetic distances between all pairwise combinations of the varieties were calculated using Jaccard's coefficient of similarity and dendrograms were constructed by the UPGMA method. The results of clustering analysis with both molecular systems showed the common genetic background of Tuscan varieties, and genetic divergence within Slovene olive germplasm. Slovenian varieties ‘Buga’, ‘Štorta’ and ‘Samo’ might represent regionally selected olives, while ‘Zelenjak’ and ‘Črnica’ are probably derived from the Central Italian region. The predominant local ‘Istrska belica’ was introduced to Slovenia independently from the other regional varieties and showed the lowest genetic similarity with the other regional varieties. This revised version was published online in August 2006 with corrections to the Cover Date.     

Genetic diversity and relationships among Lablab purpureus genotypes evaluated using RAPD as markers

Summary Genetic variation in 40 accessions of Lablab purpureus was evaluated using random amplified polymorphic DNA as markers. A high level of genetic variation in this species was detected but this was mainly restricted to the difference between cultivated and wild forms. Of the cultivated genotypes, genetic variation among Asian collections was significantly higher than that among African collections. The three most divergent cultivated genotypes were all from Asia. Four of the five wild accessions, two from Zimbabwe and the other two from Zambia, were closely related. The other one, CPI 31113 collected from Uganda, was highly divergent. The two commercial forage varieties used in Australia, Rongai from Kenya and Highworth from India, were not very different.     

The taxonomic characterisation of annual Beta germplasm in a genetic resources collection using RAPD markers

Summary Annual beets in the genus Beta section Beta represent an important genetic resource. Representative accessions of annual beets from a beet germplasm collection were analysed using RAPD to assess the patterns of variation and relationships among them. Using arbitrary primers, markers showing variation across accessions were identified. A dendrogram of similarity was produced using these molecular markers. All the accessions analysed were classified into three major groups corresponding to species or subspecies macrocarpa, adanensis and maritima. Macrocarpa was shown to be the most divergent group in this section. Using RAPD molecular markers, it was possible to ascribe an accession to one of three taxonomic groups and overcome much of the confusion encountered when morphological traits are used for identification. The group of maritima was found to be more polymorphic than either the group of macrocarpa or adanensis at both accession and subspecies levels.     

Assessment of genetic relationships in Mentha species

A set of 60 random primers was used to analyse 11accessions from six taxa of Mentha developed byCIMAP. These accessions were maintained in the nationalgene bank for medicinal and aromatic plants at CIMAP.A total of 630 bands could be detected as amplifiedproducts upon PCR amplification, out of which 589 werepolymorphic (93.5%). Further analysis of these RAPDprofiles for band similarity indices clearlydifferentiated five of the Mentha arvensis L.accessions from the rest. Among two accessions of Mentha spicata L. CIMAP/C33 could bedistinguished from CIMAP/C32. Mentha × gracilis Sole cv. cardiaca showed a muchhigher similarity with Mentha spicata L. as wellas Mentha arvensis L. which amongst themselvesshowed rather a greater distance indicating that Mentha × gracilis Sole cv. cardiaca might have evolved as a natural hybridbetween M arvensis L. and M. spicataL. In terms of uniqueness of amplified bands fordeveloping RAPD markers, it was observed that at taxalevel 298 bands were unique to one of the six taxa,singly amounting to 47.3% of total amplifiedfragments. Primers MAP 10 and 17 produced polymorphismonly in case of M. spicata L. and Menthaspicata L. cv. viridis while MAP 08 producedpolymorphic bands in all 4 other species than thesetwo. Similarly unique patterns were observeddifferentiating all six species and could be used asRAPD markers for differentiating Mentha species.     

Amplified fragment length polymorphism for variety identification and genetic diversity assessment in oleander (Nerium oleander L.)

Oleander is a Mediterranean evergreen shrub found along watercourses, gravelly places and damp slopes. It is grown widely as an ornamental for its abundant and long-lasting flowering as well as its moderate hardiness. Genetic relatedness among 71 accessions, including commercial varieties, different sources of the same varieties, and selections from the wild were investigated using amplified fragment length polymorphism (AFLP). Nine primer combinations yielded a total of 603 bands of which 241 were polymorphic. Genetic similarities among accessions were calculated according to Jaccard's Similarity Index and used to construct a dendrogram based on the unweighted pair group method using arithmetic averages. Our results show that the AFLP technique, which can simultaneously and assay a large number of loci randomly distributed in the genome, is much more informative on the genetic relationship and origin of accessions than the limited number of morphological characters conventionally used for variety discrimination. Up to about 9% molecular genetic differentiation was detected among morphologically indistinguishable provenances of the same variety; this can be partly attributed to scoring error but mainly to somatic variation occurring during vegetative propagation. On the other hand lower genetic distance values were sometimes found among varieties which differ in morphological characters and are thus commercialised with different names. The possibility of considering the amount of genetic variation within a variety as the threshold value for discrimination of initial varieties and essentially derived varieties is discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Characterization and genetic distance analysis of cassava (Manihot esculenta Crantz) germplasm from Mozambique using RAPD fingerprinting

Twenty-eight cassava genotypes from Mozambique, along with seven genotypes from Angola, Madagascar, Nigeria, Togo, Columbia, and Thailand for comparison, were fingerprinted using random amplified polymorphic DNA (RAPD) analysis. The Mozambican material represented a wide range of landraces. A total of 311 scored RAPD loci were used to calculate genetic distances between the genotypes. This revealed an average genetic distance of 3.1% between all the germplasm. The average genetic distance between the Mozambiquen genotypes was 2.7%, whilst the seven accessions from the other countries showed an average distance of 3.4%. Neighbor-joining (NJ) method cluster analysis of the genetic distance yielded a tree that did not indicate a relationship between geographic distribution and genetic diversity. This revised version was published online in August 2006 with corrections to the Cover Date.     

Genetic relationships between cultivated and wild olives of Corsica and Sardinia using RAPD markers

In order to ensure the genetic diversity of the Olea europaea complex,it is necessary to characterize the cultivated varieties and the wildpopulations. In the present study, we focused on the olives growing on twoMediterranean islands, Corsica and Sardinia. On these two islands, there areolives with many denominations, as well as forests of oleasters. Here, it wasproposed to determine the relationships among cultivated and wild olives.Some Italian denominations were studied in addition to assess the influenceof the mainland on the two islands in this respect.The 59 RAPD markers obtained showed the existence of manysynonymous, and homonymous. A dendrogram was constructed using theUPGMA method and a FCA was carried out. The results of these twoanalyses showed the existence of a genetic divergence between the oleastersand the cultivated varieties. They suggest that some of the Corsicanvarieties were probably selected from local wild forms, contrary to theSardinian varieties. They also show that there are feral forms growing onboth islands, which result from hybridization between oleasters andvarieties.     

Genetic diversity among elite Bulgarian barley varieties evaluated by RFLP and RAPD markers

Genetic variation among five elite winter barley cultivars (H. vulgare L.) currently grown in Bulgaria was assessed at the molecular level using restriction fragment length polymorphism (RFLP) and randomly amplified polymorphic DNA (RAPD) markers. The present study sampled RFLPs in four well characterized multigene families in barley: the seed storage protein loci; the 18S, 5.8S and 26S ribosomal DNA loci; the loci coding for 5S ribosomal RNA and the loci coding subunit α of ATP-A complex in the mitochondrial genome. RFLPs were detected in three out of five investigated chromosomal loci in the barley cultivars studied. RAPD assay using arbitrary 10-base primers was applied to generate amplified length polymorphic markers in barley. Overall a total of 15 polymorphic phenotypes were found among the studied barley cultivars by using 11 out of 25 tested primers. All RAPDs were considered as dominant genetic markers except for two, where PCR and Southern blot analysis indicated the presence of codominant amplification products. Five RAPD polymorphisms in F₁ and F₂ progenies of the cross between Alpha and Obzor were inherited in Mendelian fashion. The determined values for the genetic variation proved a high genetic similarity among the tested cultivars. Genetic similarity (GS) calculated from RFLP and RAPD data ranged from 0.888 to 0.997 with a mean GS – 0.933. This revised version was published online in July 2006 with corrections to the Cover Date.     

Phenotypic diversity and relationships of fruit quality traits in apricot (Prunus armeniaca L.) germplasm

Fruit quality attributes were studied for two consecutive years in forty-three apricot cultivars and selections grown in a Mediterranean climate. Physical parameters (weight, size, flesh and skin colour, percentage of blush, firmness and percentage of dry matter), chemical parameters (total soluble solids content and acidity) and sensory parameters (attractiveness, taste, aroma and texture) were evaluated. A high variability was found in the set of the evaluated apricot genotypes and significant differences were found among them in all studied quality attributes. Year-by-year variations were observed for some pomological traits such as harvest date, flesh colour, fruit weight, firmness and soluble solids content. A high correlation was found among some apricot quality attributes. In addition, principal component analysis (PCA) made it possible to establish similar groups of genotypes depending on their quality characteristics as well as to study relationships among pomological traits in the set of apricot genotypes evaluated.     

Analysis of genetic diversity in Agave tequilana var. Azul using RAPD markers

By federal law in Mexico, A. tequilana Weber var. Azul is the only variety of agave permitted for the production of any tequila. Our objective was to assay levels of genetic variation in field populations of A. tequilana var. Azul using randomly amplified polymorphic DNA (RAPD) markers. Ten plants were collected from each of four different fields, with two fields being located in each of two principal regions of Mexico for the cultivation of A. tequilana var. Azul. The two regions are separated geographically by approximately 100km. Genetic relationships between A. tequilana var. Azul and two other varieties of A. tequilana Weber, ‘Chato’ and ‘Siguin’, were also investigated using RAPDs. Among the three varieties, 19 decamer primers produced 130 markers, of which 20 (15.4%) were polymorphic betweenA. tequilana var. Chato and A. tequilana var. Siguin. The results of RAPD analysis suggest that A. tequilana var. Siguin is more closely related to A. tequilana var. Azul than is A. tequilana var. Chato. Among the 40 field selections of A. tequilana var. Azul, only 1 of124 RAPD products (0.8%) was polymorphic and 39 of 40 plants were completely isogenic. This is one of the lowest levels of polymorphism detected to date for the analysis of a crop species, and is proposed to be the result of the promotion of a single conserved genotype over many years due to an exclusive reliance on vegetative propagation for the production of new planting materials. The significance of these results is discussed in relation to breeding programs focused on the improvement of A. tequilana var. Azul. This revised version was published online in July 2006 with corrections to the Cover Date.     

RAPD analysis of genetic diversity among clones of the Ethiopian crop plant Ensete ventricosum

Random amplified polymorphic DNA (RAPD) was used to estimate genetic variability among 111 different clones of Ensete ventricosum, cultivated at 9 different collection sites in southwestern Ethiopia. PCR conditions were optimized for the amplification of DNA fragments in this crop. Out of 126 oligonucleotide primers initially screened,12 were chosen that together generated 97 reproducible polymorphic bands. Each clone proved to have a unique DNA profile, in spite of 8 duplications among the vernacular names represented in this material. The high level of genetic variability encountered is in good accordance with an outcrossing breeding system, and is also indicative of gene flow from wild enset and possibly from otherEnsete species. Genetic variation within collection sites was relatively high, with values for the Shannon-Weaver diversity index ranging from 0.44 to 0.55. A PCA (principal component analysis) demonstrated some differentiation among sites but also considerable overlapping. Partitioning the total variability at different levels with the Shannon-Weaver index shows that only14% was attributable to differences between sites and 86% to variation within sites. Pairwise comparisons of the 9 sites yielded values for Nei's unbiased genetic distances that ranged from 0.054 to 0.225.Cluster analysis as well as PCO (principal co-ordinate analysis) showed that Bonga and Chencha form a nucleus within a loose cluster, which also comprises Wolkitae, Worka, Shonae and Wondo. The remaining three sites, Answae, Setunae and Seltae, take quite isolated positions. Estimates of genetic distances did not correspond with geographical distances between collection sites. Genetic distances, as well as amount of within-site diversity, may instead be connected with the pattern of distribution for various ethnic groups in the enset-based agricultural system, and their dependency on enset as a staple food. This study is the first of its kind on enset. This revised version was published online in August 2006 with corrections to the Cover Date.     

Molecular assessment of genetic diversity in winter barley and its use in breeding

Summary During the last decades extensive progress has been achieved in winter barley breeding with respect to both, yield and resistance to fungal and viral diseases. This progress is mainly due to the efficient use of the genetic diversity present within high yielding adapted cultivars and – with respect to resistance – to the extensive evaluation of genetic resources followed by genetic analyses and introgression of respective genes by sexual recombination. Detailed knowledge on genetic diversity present on the molecular level regarding specific traits as well as on the whole genome level may enhance barley breeding today by facilitating efficient selection of parental lines and marker assisted selection procedures. In the present paper the state of the art with respect to virus diseases, i.e. Barley mild mosaic virus, Barley yellow mosaic virus, and Barley yellow dwarf virus is briefly reviewed and first results on a project aiming on a genome wide estimation of genetic diversity which in combination with data on yield and additional agronomic traits may facilitate the detection of marker trait associations and a more efficient selection of parental genotypes are presented. By field tests of 49 two-rowed and 64 six-rowed winter barley cultivars the genetic gain in yield for the period 1970–2003 was estimated at 54.6 kg ha⁻¹ year⁻¹ (r² = 0.567) for the six-rowed cultivars and at 37.5 kg ha⁻¹ year⁻¹ (r² = 0.621) for the two-rowed cultivars. Analysis of 30 SSRs revealed a non-homogenous allele distribution between two and six-rowed cultivars and changes of allele frequencies in relation to the time of release. By PCoA a separation between two and six-rowed cultivars was observed but no clear cut differentiation in relation to the time of release. In the two-rowed cultivars an increase in genetic diversity (DI) from older to newly released cultivars was detected.     

Analysis of genetic relationships among 22 European barley varieties based on two PCR markers

Two long primers of 19 (F17) and 20 (F13) nucleotides, respectively,were used in polymerase chain reactions to amplify DNA from differentcultivated barley accessions. These primers can distinguish closely relatedvarieties and, with a unique primer, all the barley accessions analysedshowed a characteristic fingerprint. Sixty per cent and 76% of thefragments generated using F13 and F17, respectively, were polymorphic.The genetic similarity values between accessions were estimated from F13and F17 data. The dendrogram and principal coordinate analysis performedwith F13 data revealed a clear separation of these varieties in accord withtheir pedigree relationships.     

A comparative assessment of DNA fingerprinting techniques (RAPD, ISSR, AFLP and SSR) in tetraploid potato (Solanum tuberosum L.) germplasm

Several DNA marker systems and associated techniques are available today for fingerprinting plant germplasm but information on their relative usefulness in particular crops is limited. The study investigated PCR based DNA fingerprinting in a set of 39 potato cultivars using RAPDs (20 primers), ISSRs (6 primers), AFLPs (2 primers) and SSRs (5 primer pairs). Results show that each of the four techniques can on their own, individually identify each cultivar, but that techniques differ in the mean number of profiles generated per primer (or primer pair) per cultivar, referred to as Genotype Index (GI). The order of merit based on this criterium and in this material was AFLPs (GI = 1.0), a multi-locus SSR (GI = 0.77),RAPDs (GI = 0.53), ISSRs (GI = 0.47) and single locus SSRs (GI = 0.36). Problems in relating banding patterns to individual loci and alleles for polyploid genomes, using these techniques as they are currently employed, are also discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Assessment of genetic diversity within and among Basmati and non-Basmati rice varieties using AFLP,ISSR and SSR markers

Molecular markers provide novel tools to differentiate between the various grades of Basmati rice, maintain fair-trade practices and to determine its relationship with other rice groups in Oryza sativa. We have evaluated the genetic diversity and patterns of relationships among the 18 rice genotypes representative of the traditional Basmati, cross-bred Basmati and non-Basmati (indica and japonica) rice varieties using AFLP, ISSR and SSR markers. All the three marker systems generated higher levels of polymorphism and could distinguish between all the 18 rice cultivars. The minimum number of assay-units per system needed to distinguish between all the cultivars was one for AFLP, two for ISSR and five for SSR. A total of 171 (110 polymorphic), 240 (188 polymorphic) and 160 (159 polymorphic) bands were detected using five primer combinations of AFLP, 25 UBC ISSR primers and 30 well distributed, mapped SSR markers, respectively. The salient features of AFLP, ISSR and SSR marker data analyzed using clustering algorithms, principal component analysis, Mantel test and AMOVA analysis are as given below: (i) the two traditional Basmati rice varieties were genetically distinct from indica and japonica rice varieties and invariably formed a separate cluster, (ii) the six Basmati varieties developed from various indica × Basmati rice crosses and backcrosses were grouped variably depending upon the marker system employed; CSR30 and Super being more closer to traditional Basmati followed by HKR228, Kasturi, Pusa Basmati 1 and Sabarmati, (iii) AFLP, ISSR and SSR marker data-sets showed moderate levels of positive correlation (Mantel test, r = 0.42–0.50), and (iv) the partitioning of the variance among and within rice groups (traditional Basmati, cross-bred Basmati, indica and japonica) using AMOVA showed greater variation among than within groups using SSR data-set, while reverse was true for both ISSR and AFLP data-sets. The study emphasizes the need for using a combination of different marker systems for a comprehensive genetic analysis of Basmati rice germplasm. The high-level polymorphism generated by SSR, ISSR and AFLP assays described in this study shall provide novel markers to differentiate between traditional Basmati rice supplies from cheaper cross-bred Basmati and long-grain non-Basmati varieties at commercial level.The first two authors have equal contribution     

Assessment of natural and induced genetic variation in Alstroemeria using random amplified polymorphic DNA (RAPD) markers

Summary We have used random amplified polymorphic DNA (RAPD) markers to study genetic variation in Alstroemeria. The first objective was to examine the discriminatory power of RAPD markers in different genotypes of Alstroemeria obtained by traditional breeding. All genotypes examined, including commercial Alstroemeria varieties, could be distinguished on the basis of their RAPD profiles. Progeny plants could be distinguished from their parents. A second objective of this study was to investigate whether RAPD markers can be used as a routine tool to detect mutant plants, as an alternative to glasshouse testing. To address this objective, we analysed Alstroemeria plants that carried phenotypically visible mutations that either were induced by irradiation using X-rays or were the result of somaclonal variation. In eight out of a total of 13 mutant Alstroemeria plants obtained after irradiation or tissue culture we detected no polymorphisms when compared to control plants that were considered to be non-mutated. Only in five of the mutant plants analysed we detected one to two polymorphisms. These results suggest that frequent genome rearrangements had not occurred in the mutant plants analysed. These results also demonstrate that the RAPD technique is an inappropriate tool for the rapid screening of Alstroemeria for induced variation. It that the RAPD technique is an inappropriate tool for the rapid screening of Alstroemeria for induced variation. It seems probable that this conclusion would be equally applicable in other plant genera in which induced variation has occurred. However, the RAPD technique is a simple and effective tool for genetic fingerprinting of Alstroemeria varieties, provided their differences are due to sexual propagation.     

A comparative analysis of the genetic relationships between rye cultivars using RFLP and RAPD markers

Summary The genetic similarities of eight closely related rye cultivars were estimated using two molecular marking techniques: restriction fragment length polymorphism (RFLP) and random amplified polymorphic DNA (RAPD). Cultivars were evaluated for variation by 11 random cDNA and genomic clones used in combination with four restriction enzymes and 40 decamer primers. A total of 53 polymorphic RFLP fragments and 94 polymorphic RAPD fragments were observed. Based on the presence/absence of fragments, two genetic similarity matrices were calculated which were then used in cluster analysis. Differences between pair of cultivars were observed in RFLP and RAPD dendrograms. RFLP analysis produced estimates of genetic relationships more in accordance with the partially known pedigree of the cultivars than did RAPD analysis. The use of bulk samples of DNA in these analyses affected the sensitivity of RAPD assays more strongly. Dendrograms which took into account all fragments produced, either by RFLP or RAPD, reflected better the relationships between cultivars than did dendrograms based on only one type of marker. This reflects the importance of the number of markers used in determining the genetic relationships between genotypes.