Pedigree, RAPD and simplified AFLP-based assessment of genetic relationships among Avena sativa L. cultivars

Two molecular marker techniques: RAPD and simplified ^PstIAFLP have been compared in order to decide on, which technique is better suited to genetic characterization of oat (Avena sativa L.) cultivars. It was investigated, if the same pattern of variability is revealed by two approaches and whether the observed molecular variability reflects pedigree-based relationships. Polymorphic RAPD and ^PstIAFLP markers were sufficient to distinguish all analysed cultivars, demonstrating the usefulness of both methods for cultivar identification. Genetic similarity estimates derived from RAPD, simplified ^PstIAFLP and combined RAPD and ^PstIAFLP data were compared with coefficients of parentage (COP). Molecular markers-based mean genetic similarities were considerably greater than mean COP value. Correlation coefficients between COP and genetic similarities calculated from RAPD, ^PstIAFLP and combined molecular data were very low and not significant. A better correlation (0.50) was found between similarity estimates derived from RAPD and ^PstIAFLP markers. Four separate dendrograms were constructed based on pedigree and molecular analyses using a neighbor-joining algorithm (NJ). The dendrograms were compared and found to be topologically different. The results of this study showed, that both molecular techniques can be conveniently used for genetic characterization of oat cultivars, however ^PstIAFLP would be the method of choice due to the higher efficiency and reproducibility. This revised version was published online in August 2006 with corrections to the Cover Date.     

Genetic effects on biomass yield in interspecific hybrids between Brassica napus and B. rapa

This study was conducted to estimate the genetic effects on biomass yield in the interspecific hybrids between Brassica napus and B. rapa, and to evaluate the relationship between parental genetic diversity and its effect on biomass yield of interspecific hybrids. Six cultivars and lines of oilseed B. napus and 20 cultivars of oilseed B. rapa from different regions of the world were chosen to produce interspecific hybrids using NC design II. Obvious genetic differences between B. rapa and B. napus were detected by RFLP. In addition, Chinese B. rapa and European B. rapa were shown genetically differences. Plant biomass yield from these interspecific hybrids were measured at the end of flowering period. Significant differences were detected among general combining ability (GCA) effects over two years and specific combining ability (SCA) effects differences were detected in 2000. The ratios of mean squares, (σ² _GCA(f) + σ² _GCA(m)) / (σ² _GCA(f) + σ² _GCA(m) + σ² _SCA), were 89% and 88% in 1999 and 2000, respectively. This indicates that both additive effects and non-additive effects contributed to the biomass yield of interspecific hybrids and the former played more important role. Some European B. rapa had significant negative GCA effects while many of Chinese B. rapa had significant positive GCA effects, indicating that Chinese B. rapa may be a valuable source for transferring favorable genes of biomass yield to B. napus. Significant positive correlation between parental genetic distance and biomass yield of interspecific hybrids implies that larger genetic distance results in higher biomass yield for the interspecific hybrids. A way to utilize interspecific heterosis for seed yield was discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

The production of multispecific octoploids from Fragaria species and the cultivated strawberry

Summary A method of incorporating genetic material from five species of Fragaria and the cultivated strawberry into fertile octoploids is described. A synthetic octoploid derived from a hexaploid x diploid hybrid was crossed to octoploid cultivar breeding lines until a BC₂ hybrid was produced. A second synthetic octoploid in which two diploid species and a tetraploid species were combined was crossed to a cultivated strawberry to produce a hybrid breeding clone. The two breeding clones were crossed and 222 seedlings were produced. The seedlings were generally vigorous and fruitful, some having commercial potential.     

Genetic variance components and genetic effects among eleven diverse upland cotton lines and their F2 hybrids

Selecting high yielding upland cotton, Gossypium hirsutum L. lines with improved fiber quality is a primary breeding goal. A diverse set of ten cultivars and one breeding line were crossed in a half diallel. Parents and F₂ hybrids were grown in three environments at Mississippi State, MS. Ten agronomic and fiber traits were analyzed by a mixed linear model approach based on the additive-dominance genetic model. Variance component, genetic effects and genetic correlations were calculated. ‘Acala Ultima’ was a desirable general combiner for fiber length, uniformity, strength, micronaire, lint percentage, and boll weight. ‘FiberMax 966’ was a desirable general combiner for fiber length, uniformity, strength, and all agronomic traits. ‘Tamcot Pyramid’ and M240 were poor general combiners for both fiber and agronomic traits. ‘Coker 315’ was a good general combiner for fiber length, uniformity, micronaire, boll weight, boll number, and yield. Heterozygous dominance effects were associated with several crosses, which suggest their use as hybrids.     

Fingerprinting temperate <Emphasis Type="Italic">japonica</Emphasis> and tropical <Emphasis Type="Italic">indica</Emphasis> rice genotypes by comparative analysis of DNA markers

This paper describes the relative efficiency of three marker systems, RAPD, ISSR, and AFLP, in terms of fingerprinting 14 rice genotypes consisting of seven temperatejaponica rice cultivars, three indica near-isogenic lines, three indica introgression lines, and one breeding line of japonica type adapted to high-altitude areas of the tropics with cold tolerance genes. Fourteen RAPD, 21 ISSR, and 8 AFLP primers could produce 970 loci, with the highest average number of loci (92.5) generated by AFLP. Although polymorphic bands in the genotypes were detected by all marker assays, the AFLP assay discriminated the genotypes effectively with a robust discriminating power (0.99), followed by ISSR (0.76) and RAPD (0.61). While significant polymorphism was detected among the genotypes of japonica and indica through analysis of molecular variance (AMOVA), relatively low polymorphism was detected within the genotypes of japonica rice cultivars. The correlation coefficients of similarity were significant for the three marker systems used, but only the AFLP assay effectively differentiated all tested rice lines. Fingerprinting of backcross-derived resistant progenies using ISSR and AFLP markers easily detected progenies having a maximum rate of recovery for the recurrent parent genome and suggested that our fingerprinting approach adopting the ‘undefined-element-amplifying’ DNA marker system is suitable for incorporating useful alleles from the indica donor genome into the genome of temperate japonica rice cultivars with the least impact of deleterious linkage drag.     

Heterosis and heritability in crosses among Asian and Ethiopian parents of hot pepper genotypes

Hot pepper is the most important worldwide grown and consumed spice and vegetable crop. Though hybrid breeding has been proposed for genetic improvement in the crop, but there is lack of information on heterosis in crosses among crop genotypes in Ethiopia. Twelve genotypes (nine Asian and three Ethiopian parents) of hot pepper were crossed in 2003 cropping season in a half-diallel fashion to fit Griffing’s fixed effect model analysis. An open field experiment was conducted in 2004/2005 to investigate heterosis for fourteen traits in 66 F₁ hybrids grown together with their 12 selfed parents. Highly significant genotypic differences were observed for all the traits except for leaf area. Variance component due to specific combining ability (dominance) were larger than that due to general combining ability (additive) for each of the studied traits with few exceptions. Broad sense heritability (H _b²) for fruit traits were more than 60% and with wide gap from narrow sense heritability (h _n²) for most of the important traits like number of fruit per plant (H _b² = 88.3% and h _n² = 46.0%), days to maturity (H _b² = 87.2% and h _n² = 23.1%) and dry fruit yield per plant (H _b² = 72.6% and h _n² = 14.6%). Maximum heterosis over mid-parent and better-parent, and economic superiority of hybrid over standard check were recorded, respectively for dry fruit yield per plant (163.8, 161.8 and 92.1%), number of fruits per plant (104.4, 79.6 and 136.4%) and days to maturity (−29.8, −31.5 and −23.6%). These observations suggested a possibility of utilizing dominance genetic potentiality available in diverse genotypes of the crop by heterosis breeding for improving hot pepper to the extent of better economic return compared to the current commercial cultivar under production in the country. Low narrow sense versus very high broad sense heritability for days to maturity and dry fruit yield per plant could be a sign for achievability of earliness and high fruit yield using heterosis in hot pepper. The maximum heterobeltiosis were recorded either from F₁s obtained from Ethiopian and Asian crosses or from within Asian crosses, suggesting the possibility of maximizing heterosis by considering genetically diverse parental genotypes. The manifestation of highest heterosis in hybrids from among Asian lines indicated existence of genetic diversity among Asian genotypes and the potentiality for improvement of hot pepper using genotypes from different regions of the world along with elite inbred lines from local cultivars.     

Identification of pathogenic races ofPhytophthora fragariae Hickman in Germany

Summary The fungusPhytophthora fragariae Hickman is the causal agent of red stele disease in strawberry (Fragaria × ananassa), this being a major disease in many areas with cool and moist conditions. Success of resistance breeding can be nullified by the appearence of specific races of the fungus capable of overcoming the introduced resistance. In some countries (USA, UK, Japan and Canada) races were identified by using a differential set of strawberry cultivars. The absence of an international standard differential set and the use of different test methods make a comparison of the identified races difficult or even lead to contradictory results for one variety/race combination. The aim of this study was to obtain information about the spectrum of pathogenic races in Germany as a basic contribution to research on resistance breeding against the fungus. The susceptibility of different strawberry cultivars to German isolates ofP. fragariae was evaluated. The inoculation was done by modifying a method described by Milholland et al. (1989). Rootedin vitro plants, four weeks after transferring them to the soil, were used for the investigation. Inoculation was done with a zoospore suspension of defined concentration. Up to now three German isolates, G-1, G-2, and G-3, can be separated by their ability to infect and produce oospores in the roots of the strawberry cultivars ‘Senga Sengana’, either ‘Saladin’, ‘Redgauntlet’ or ‘Climax’ andFragaria chiloensis clone ‘YaquinaB’. These results confirm the existence of pathogenic races ofP. fragariae in Germany and should be taken into consideration for resistance breeding against the fungus.     

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.     

Cytological studies of 2n male gamete formation in sugarcane, Saccharum L.

The germplasm for modern sugarcane cultivars (Saccharum spp. hybrids)has been derived principally from S. officinarum (2n = 80), and S. spontaneum (2n = 40 to 128). Diploid gamete formation has been significant in developing cultivated sugarcane, but the cytological basis for the processes involved is not clearly understood. This research investigated microsporogenesis in nine clones of Saccharum spp. Hybrids and in S. officinarum and S. spontaneum. Diploid gamete formation occurred in all 11 lines, but was least frequent in S. spontaneum and S. officinarum which produced 0.5% and 0.8%2n gametes, respectively. In the hybrid lines, 2n gametes were formed infrequencies ranging from 0.9% to 4.4%. Cytological evidence was obtained for dyad and triad formation during microsporogenesis. Detailed analysis of chromosome behaviour at meiosis indicated that 2n male gamete formation is probably attributable to the absence of cytokinesis rather than a combination of asynchrony and non-disjunction. The clones were ranked on the basis of the frequencies with which they formed 4 × 1n microspores and the data were analysed using χ ² tests for homogeneity. These established that theSaccharum spp. hybrids could be designated as either ‘high’ or ‘low’ frequency haploid gamete producers. Conversely, the latter group, which formed diploid gametes most frequently (2.2%–4.4%), can be described as high frequency diploid gamete producers. The identification of clones most frequently forming diploid gametes may facilitate the more rapid recovery of desirable sugarcane genotypes because such clones could be selected for preferential use in clonal improvement. This revised version was published online in July 2006 with corrections to the Cover Date.     

Hybrid performance and heterosis in strawberry (Fragaria × ananassa Duchesne), regarding acidity,soluble solids and dry matter content in fruits

A top‐cross‐mating design among 29 S₄ inbred lines and tester (cultivar ‘Dukat’) was carried out to study their breeding value in terms of general combining ability (GCA). The objectives of this study were to evaluate the acidity, soluble solids and dry matter contents in fruits of progeny F₁ in comparison with S₄ inbred lines as well as the cultivars (S₀); identify strawberry genotypes with high value of GCA for use in cultivar development; and determine mid‐parent heterosis regarding S₄ inbred lines and cultivated strawberry. The 2‐year observations showed statistically significant differences between tested genotypes in terms of the studied traits. The highest breeding value based on GCA was estimated for Chandler 123‐5 for soluble solids and dry matter content, and Kent 7‐6 for acidity. Estimated mid‐parent heterosis had positive and negative values. The highest heterosis in terms of extract and dry matter content (26.71% and 17.50%, respectively) occurred in the offspring Chandler 123‐5 × ‘Dukat’, but as regards acidity in hybrid Chandler 123‐22 with cv. ‘Dukat’. The study of genetic divergence by dendrograms may help to identify parents suitable for obtaining hybrids with higher heterosis effects.     

Hybrid performance and AFLP- based genetic similarity in faba bean

Successful prediction of heterosis and performance of F₁-hybrids from the genetic similarity of their parents based on molecular markers has been reported in several crops and can be very helpful in hybrid breeding. The relationship between genetic similarities based on amplified fragment length polymorphism (AFLP) of 18 European faba bean lines and their hybrid performance and heterosis was investigated. Parental lines, 62 F₁-hybrids and their F₂-progenies were evaluated in field trials in four environments in Germany for seed yield, 1,000-seed weight and plant height. Results clearly demonstrated a stable superiority of the hybrids over their inbred parents and elite check cultivars, and showed a marked and varying amount of heterosis. Parental seed yield and F₂-hybrid yield were promising as predictors for F₁-hybrids. AFLP analysis of the 18 inbred lines using 26 EcoRI/MseI primer combinations resulted in 1202 polymorphic fragments. Cluster analysis based on genetic similarity estimates unambiguously identified pedigree-related inbred lines. No clear separation of the 18 inbred lines into subgroups was detected. Correlation coefficients between genetic similarity estimates and either heterosis or F₁-hybrid performance were small and not useful. Also correlations between specific genetic similarity and specific combining ability were too small for all traits to be of predictive value. Results showed that AFLP-based genetic similarities are not useful to predict the performance of hybrids or heterosis within the elite European faba bean gene pool.     

Introgression of unique characteristics of floral initiation under 24 hour day-length of Fragaria chiloensis ‘CHI-24-1’ into F. × ananassa

A unique flower initiation of the wild Junebearing strawberry strain ‘CHI-24-1’ in Fragaria chiloensis occurs under 24 h DL and high temperature conditions. To introduce the floral initiation characteristics of ‘CHI-24-1’ into cultivated strawberries of F. × ananassa, a cross pollination was conducted between ‘CHI-24-1’ and the Japanese short-day type strawberry cultivar ‘Nyoho’. The floral initiation of ‘CHI-24-1’ was induced in both parent and daughter plants linked with runners under a 24 h DL and 23/20 ^∘C, but not 8 and 16 h DLs at the same temperatures. Of the 21 F1 hybrids grown under the 24 h DL, 12 showed flower truss production in the parent and/or daughter plants linked with runners. Among 64 F1 hybrids, 26 exposed to 8, 16 and 24 h DLs for 30 days produced no flower trusses. However, 32, one and five F1 hybrids produced flower trusses under the 24 h DL alone, 8 h DL alone and both the 8 and 24 h DLs, respectively. The results of the experiments indicated that none of the F1 hybrids were day-neutral plants, but approximately 60% had the characteristics of floral initiation under 24 h DL, which was inherited from the pollen parent of ‘CHI-24-1’. The importance of the unique floral initiation characteristics under 24 h DL with high temperature for strawberry breeding was discussed.     

Embryonic heterosis in the linolenic acid content of Matthiola incana seed oil

Summary The fatty acid composition of seed-oil of breeding lines and F₁ hybrids of Matthiola incana was analyzed, using direct esterification and gas chromatography. The breeding lines tested differed significantly with respect to the levels of palmitic, oleic, linoleic and linolenic acids. Embryonic-stage heterosis in linolenic acid concentration was demonstrated by F₁ hybrid seeds, derived from mating horticulturally different lines of M. incana. Linolenic acid content was negatively correlated with both oleic acid content (r=–0.85) and linoleic acid content (r=–0.66). None of the breeding lines or the F₁ hybrids significantly passed the limit of 67% linolenic acid. Possible genetic and biochemical explanations for the above phenotypic data are discussed.     

A comparison of genetic relationship measures in strawberry (Fragaria × ananassa Duch.) based on AFLPs, RAPDs, and pedigree data

Nineteen of the major strawberry (Fragaria × ananassa Duch.) cultivars grown in the UnitedStates and Canada were examined for AFLP markerpolymorphisms. For the AFLP reactions, the EcoRI-ACC primer was used in combination with fourMseI primers (MseI-CAC, MseI-CAG,MseI-CAT, or MseI-CTT). Each set ofprimers produced 46–66 scorable fragments ranging insize between 50 and 500 bp. The polymorphic fragmentsproduced from each set of primers were more thansufficient to distinguish among all the cultivars,demonstrating the usefulness of AFLP markers forcultivar identification. Similarity coefficients werecalculated based on data from 228 AFLP markers anddata from 15 previously characterized RAPD markers. The RAPD markers had been specifically selected forfingerprinting purposes because they succesfullydistinguish 41 strawberry cultivars, including the 19cultivars analyzed in this study. Separatedendrograms were constructed based on analysis of theAFLP and RAPD marker data using a neighbor-joiningalgorithm. The dendrograms were compared and found tobe very different. Correlations between similaritycoefficients calculated from AFLP marker data,similarity coefficients calculated from RAPD markerdata, and coefficients of coancestry calculated frompedigree information were evaluated. Interestingly,a better correlation with the coefficients ofcoancestry was observed with the RAPD marker data thanwith the AFLP marker data.     

Cultivar identification and genetic map of mango (Mangifera indica)

Amplified Fragment Length Polymorphism (AFLP) information was used for identification of mango (Mangifera indica L.) cultivars, for studying the genetic relationship among 16 mango cultivars and seven mango rootstocks and for the construction of a genetic linkage map. Six AFLP primer combinations produced 204 clear bands and on the average 34 bands for each combination. The average Band-Sharing between cultivars and rootstocks was 83% and 80%, respectively. The average Band-Sharing for mango is 81%. The probability of obtaining a similar pattern for two different mango cultivars and rootstocks is 6 × 10⁻³and 2 × 10⁻³, respectively. A preliminary genetic linkage map of the mango genome was constructed, based on the progeny of a cross between ‘Keitt’ and ‘Tommy-Atkins’. This linkage map consists of 13 linkage groups and covers 161.5 cm defined by 34 AFLP markers. This revised version was published online in August 2006 with corrections to the Cover Date.     

AFLP analysis of genetic diversity within and between populations of perennial ryegrass (Lolium perenne L.)

Amplified fragment length polymorphism (AFLP) analysis has been used to measure genetic diversity in perennial ryegrass (Lolium perenne L.) and to relate intra- and interpopulation variation to breeding history. Cluster analysis of AFLP data from contrasting populations showed features consistent with the origins of these varieties. Significant differences in intrapopulation diversity were detected and partial separation of different cultivars was observed. Restricted base cultivars, derived from small numbers of foundation clones, were suitable for this type of study, allowing near complete discrimination of closely related cultivars. Analysis of bulked samples was based on the pooling of genomic DNA from 20 individuals from 6 selected populations. Cluster analysis of AFLP data from bulked samples produced a phenogram showing relationships consistent with the results of individual analysis. AFLP profiling provides an important tool for the detection and quantification of genetic variation in perennial ryegrass. This revised version was published online in August 2006 with corrections to the Cover Date.     

Agronomic and qualitative traits of T. turgidum ssp. dicoccum genotypes cultivated in Italy

Summary The increasing popularity of organic agriculture and health food products has led to a renewed interest in hulled wheat species such as emmer (Triticum turgidum ssp. dicoccumSchubler). Knowledge on agronomic and quality traits is required for effective and efficient use of germplasm collections in breeding programs. The objective of this study was to estimate agronomic and grain quality traits of emmer wheat cultivated in Italy. A total of 20 emmer accessions consisting of landraces, breeding lines or cultivars selected from landraces and modern cultivars were examined under low input conditions. The study was conducted for three successive years (2002–2004) at one location of Southern Italy (Foggia). The entries were characterized for agronomic and qualitative traits [grain yield (t ha⁻¹), thousand grain weight (g), test weight (kg hl⁻¹), grain protein content (%), HMWG composition, dry gluten content (%), gluten index and yellow index, alveograph indices and Total Organic Matter (TOM) on cooked pasta]. The results showed a large genetic variability for most of the traits measured and, even if most of the accessions showed inferior bread- and pasta-making performance, modern cultivars exhibited improved quality traits with some potential to perform healthy and tasty food.     

Relationship between heterosis and genetic distance based on morphological traits and AFLP markers in pepper

Genetic diversity is considered as one of the criteria for the selection of parents for hybrid breeding. The present study was undertaken to evaluate genetic divergence among seven pepper cultivars and to assess the relationship between heterosis and parental genetic distance. Twenty‐one F₁ hybrids and seven parents were evaluated for 15 morphological characters in a greenhouse and in the field. The parents were examined for DNA polymorphisms using six amplified fragment length polymorphism (AFLP) primer combinations. Cluster analysis using two genetic distance measures grouped the seven parents differently. Mid‐parent and high‐parent heterosis was observed for most characters. Most hybrids outperformed the parental lines for fruit yield, earliness and plant height. Morphological and AFLP‐based distance measurements were efficient enough to allocate pepper genotypes into heterotic groups. The correlations of morphological distances with mid‐parent heterosis were significant for days to flowering and maturity, suggesting earliness can be predicted from morphological distances of parental lines. However, the correlations of AFLP‐measured genetic distances with mid‐ and high‐parent heterosis were non‐significant for all characters, except for fruit diameter, and proved to be of no predictive value.     

Development of AFLP and derived CAPS markers for root-knot nematode resistance in cotton

Resistance to root-knot nematode (Meloidogyne incognita) is determined by a single major gene rkn1 in Gossypium hirsutum Acala NemX cotton. Bulked segregant analysis (BSA) combined with amplified fragment length polymorphism (AFLP) was used to identify molecular markers linked to rkn1. DNA pools from homozygous susceptible (S) and resistant (R) bulks of an F_2:3 originating from the intraspecific cross NemX × SJ-2 were screened with 128 EcoR1/Mse1 primer combinations. Putative AFLP markers were then screened with 60 F_2:7 RIL plants and four AFLP markers were found linked to rkn1. The linkage of AFLP markers to rkn1 was also confirmed in a F₂ population. The closest AFLP marker was converted to a cleaved amplified polymorphic sequence (CAPS) marker (designated GHACC1) by aligning the sequences from both susceptible and resistant parents. GHACC1 linkage to rkn1 was confirmed in the F₂ (1R:3S), F_2:7 RIL (1R:1S) and the backcross population SJ-2 × F₁ (NemX × SJ-2) (1 heterozygous: 1 homozygous). The four AFLP markers, GHACC1 plus two SSR markers (CIR316 and BNL1231) linked to rkn1 from previous work were mapped to intervals of 2.6–14.2 cM from the rkn1 locus, and the genomic region around rkn1 was spanned to about 28.2 cM in the F_2:7 population. The PCR-based GHACC1 and CIR316 markers were tested on 21 nematode resistant and susceptible cotton breeding lines and cultivars. GHACC1 was suitable for nematode resistance screening within G.␣hirsutum, but not G. barbadense, whereas CIR316 was useful in both species, indicating their␣potential for utilization in marker-assisted selection.     

Identification of commercial chicory cultivars for hydroponic forcing and their phenetic relationships revealed by random amplified polymorphic DNAs and amplified fragment length polymorphisms

One‐hundred and twenty‐four amplified fragment length polymorphism (AFLP) and 49 random amplified polymorphic DNA (RAPD) markers have been used to distinguish between 20 and 23 commercial chicory cultivars, respectively. These were all Cichorium intybus var. foliosum F₁ hybrids, currently used in hydroponic forcing. Five‐hundred and twenty RAPD primers (OPERON) were tested, of which 156 resulted in reproducible patterns and 26 yielded polymorphisms. Two‐hundred and fifty‐six AFLP primer‐combinations were tested and six combinations were selected for identification purposes. Similarity indices were measured and clustering has been done using pairwise comparison. Both types of marker provide similar conclusions. Two major clusters are formed, representing late and early cultivars. All cultivars were identified using 10 informative RAPD primers or three AFLP primer combinations. A low degree of polymorphism was detected between some early cultivars, suggesting a narrow genetic base in their breeding strategy.