Nuclear DNA Amounts in Pteridophytes

DNA amounts (C-value and genome size) are much-used biodiversitycharacters. A workshop held at Kew in 1997 identified majorgaps in our knowledge of plant DNA amounts, recommending targetsfor new work to fill them. Murray reviewed non-angiosperm plantsnoting that representation of pteridophyte species (approx.0.42%) was poor, while locating C-value data for them was verydifficult. The workshop confirmed the need to make data forother groups besides angiosperms accessible for reference purposes.This paper pools DNA C-values for 48 pteridophyte species fromeight original sources into one reference source, and fulfilsa key workshop recommendation for this group. Comparing thesedata shows that nuclear 1C-values in pteridophytes vary approx.1000-fold, from 0.055 pg in Selaginella species to about 55pg in Ophioglossum petiolatum. Genome size estimates for 25pteridophytes vary approx. 200-fold from 0.055 to 10.7 pg, andthe mean genome sizes in diploids and polyploids (5.15 and 4.59pg, respectively) are not significantly different. Wider comparisonsshow that ranges of genome sizes in the major groups of landplants are very different. Those in bryophytes and pteridophytesare narrow compared with those in gymnosperms and angiosperms.The data indicate that the origin of land plants possibly involveda first major increase in genome size in the evolution of vascularplants, while a second such increase occurred later in gymnosperms.C-values for pteridophytes remain very few, but conversely opportunitiesfor new work on them are many. Copyright 2001 Annals of BotanyCompany Pteridophyte DNA amounts, DNA C-values, nuclear genome sizes     

Genome Size in Chinese Soybean Accessions--Stable or Variable?

Variation in genome size up to 1.12-fold has been recently reportedin 90 Chinese accessions ofGlycine max (soybean). Generallysuch results have to be viewed with reservation if rigorousinternal standardization and control tests for the repeatabilityof the results have not been done. Therefore, we reinvestigatedten accessions (five allegedly ranking high and five low) forgenome size using propidium iodide flow cytometry and Feulgendensitometry. Using flow cytometry, the maximum difference betweenaccessions was 1.018-fold (non-significant); the differencebetween the means of the high-ranking and low-ranking groupwas 1.002-fold (non-significant). With Feulgen densitometry,the maximum difference between accessions was 1.034-fold (non-significant).The present data suggest genome size constancy, in terms ofcytometric evidence, for the Chinese soybean accessions in question.Likewise, no reasonable evidence was obtained for a differencebetween Chinese and American soybeans. Copyright 1999 Annalsof Botany Company Glycine max, Chinese soybeans, U.S. soybeans, genome size variation, propidium iodide flow cytometry, Feulgen densitometry.     

Nuclear DNA Amounts in Angiosperms and their Modern Uses--807 New Estimates

The DNA amount in the unreplicated haploid nucleus of an organismis known as its C-value. C-values differ about 1000-fold amongangiosperms and are characteristic of taxa. The data are usedin many biological fields, so they should be easily available.Values for 2802 angiosperm species (1%) were estimated during1950–1997, and five collected lists of C-values were publishedfor reference purposes during 1976–1997. Numbers of newangiosperm C-values published recently remained high, necessitatinga further supplementary list. This paper lists DNA C-valuesfor 807 angiosperm species from 70 original sources, including520 (75.2%) from sources published after 1996, and 691 for speciesnot included in any of the previous five lists. There is a continuingneed to estimate accurate DNA C-values for plant taxa, as shownin a workshop on this biodiversity topic sponsored by Annalsof Botany and held at Kew in 1997. Its key aim was to identifymajor gaps in our knowledge of plant DNA amounts and to recommendtargets and priorities for new work to fill them. A target ofestimating first C-values for the next 1% of angiosperm speciesin 5 years was set. The proportion of such C-values in the presentwork (85.6%) is very high; and the number being published (approx.220 per annum) has never been exceeded. In 1997, C-values werestill unknown for most (68%) families, so a target of completecoverage was set. This paper includes first C-values for 12families, but as less than 2% of such values listed here targetednew families, the need to improve familial representation remains.Copyright 2000 Annals of Botany Company Angiosperm DNA amounts, DNA C-values, nuclear genome sizes, plant DNA database     

New reports of nuclear DNA content for 407 vascular plant taxa from the United States

Background and Aims

The amount of DNA in an unreplicated haploid nuclear genome (C-value) ranges over several orders of magnitude among plant species and represents a key metric for comparing plant genomes. To extend previously published datasets on plant nuclear content and to characterize the DNA content of many species present in one region of North America, flow cytometry was used to estimate C-values of woody and herbaceous species collected in Wisconsin and the Upper Peninsula of Michigan, USA.

Methods

A total of 674 samples and vouchers were collected from locations across Wisconsin and Michigan, USA. From these, C-value estimates were obtained for 514 species, subspecies and varieties of vascular plants. Nuclei were extracted from samples of these species in one of two buffers, stained with the fluorochrome propidium iodide, and an Accuri C-6 flow cytometer was used to measure fluorescence peaks relative to those of an internal standard. Replicate extractions, coefficients of variation and comparisons to published C-values in the same and related species were used to confirm the accuracy and reliability of our results.

Key Results and Conclusions

Prime C-values for 407 taxa are provided for which no published data exist, including 390 angiosperms, two gymnosperms, ten monilophytes and five lycophytes. Non-prime reports for 107 additional taxa are also provided. The prime values represent new reports for 129 genera and five families (of 303 genera and 97 families sampled). New family C-value maxima or minima are reported for Betulaceae, Ericaceae, Ranunculaceae and Sapindaceae. These data provide the basis for phylogenetic analyses of C-value variation and future analyses of how C-values covary with other functional traits.     

Allium cepa L. Cultivars from Four Continents Compared by Flow Cytometry show Nuclear DNA Constancy

In 1965 Van't Hof estimated the nuclear DNA amount of an unidentifiedAllium cepa L. cultivar as 2C = 33.55 pg (Experimental CellResearch39: 8–58). This value has been adopted by commonusage as the main calibration standard for angiosperm DNA C-valueestimations. However, different cultivars have been used whileassuming species DNA C-value constancy. Surprisingly this assumptionhas never been tested. A. cepa is an outbreeder with telomericheterochromatic segments, so intraspecific variation in C-value,possibly correlated with environmental factors as seen in Zeamays L., might be expected. We used laser flow cytometry tocompare nuclear DNA amounts in roots of six A. cepa cultivarsused as calibration standards or from different environments.Tissues from one cultivar, or similar volumes of tissue fromtwo cultivars, were run and the variance between nuclei in 2Cpeaks compared. Only one shoulderless 2C peak was seen for allpairs of co-chopped cultivars. Thus, no large differences inC-value between cultivars from different environments were found.Moreover, comparing cultivars run singly or as pairs showedno evidence for increased variation in 2C peaks in the latter,and hence of critical differences in DNA amounts between ‘AilsaCraig’ and another cultivar. Such variation was insufficientto make their use as alternative calibration standards, or thepractice of imputing Van't Hof's original C-value estimate tothem, unacceptable for most practical purposes. Given the mechanismsknown which can generate genome size variation, the degree ofconstancy in DNA C-value found seems remarkable. Copyright 2000Annals of Botany Company Allium cepa, onion cultivars, calibration standards, DNA C-value constancy, flow cytometry     

Nuclear DNA C-values for biodiversity screening: Case of the Lebanese flora

The geographic position of Lebanon in the Mediterranean basin at the transition of two major landmasses, Eurasia and Africa, has contributed to its high plant diversity and makes its flora particularly interesting to study. This paper contributes to the plant DNA C-value database of native Lebanese taxa. These data should reinforce biodiversity evaluation, systematic and evolution studies involving processes of speciation such as polyploidisation. C-values have been estimated by flow cytometry using propidium iodide as intercalary fluorochrome stain. Each sample comprised at least five individuals. Where possible, several populations were measured for each species. This study presents C-values for 225 taxa belonging to 55 families and 141 genera. C-values are novel for 193 taxa including 126 plants endemic to the Eastern Mediterranean region. These are the first values for 50 genera. In this panel, genome size ranged from 1C = 0.28 pg in Hypericum thymifolium to 54.69 pg in Fritillaria alfredae. The life growth form and life cycle type are analysed according to the genome size class. Cases of polyploidy are reported for some species usually considered as only diploid. Examination of C-value variation through flow cytometry constitutes a powerful tool to screen taxonomic heterogeneity, opening further investigations.     

First nuclear DNA C-values for 18 eudicot families

BACKGROUND AND AIMS: A key target set at the second Plant Genome Size Workshop, held at the Royal Botanic Gardens, Kew in 2003, was to produce first DNA C-value data for an additional 1 % of angiosperm species, and, within this, to achieve 75 % familial coverage overall (up from approx. 50 %) by 2009. The present study targeted eudicot families for which representation in 2003 (42.5 %) was much lower than monocot (72.8 %) and basal angiosperm (69.0 %) families. METHODS: Flow cytometry or Feulgen microdensitometry were used to estimate nuclear DNA C-values, and chromosome counts were obtained where possible. KEY RESULTS: First nuclear DNA C-values are reported for 20 angiosperm families, including 18 eudicots. This substantially increases familial representation to 55.2 % for angiosperms and 48.5 % for eudicots. CONCLUSIONS: The importance of targeting specific plant families to improve familial nuclear DNA C-value representation is reconfirmed. International collaboration will be increasingly essential to locate and obtain material of unsampled plant families, if the target set by the second Plant Genome Size Workshop is to be met.     

Genome size in Dahlia Cav. (Asteraceae–Coreopsideae)

The genus Dahlia (Asteraceae–Coreopsideae) is monophyletic according to a recent DNA phylogeny (ETS and ITS of rDNA). Traditionally, the genus has been divided into sections, but these have been shown not to be monophyletic. We have studied variation in genome size (DNA C-values) in a sample of species to investigate the possible effects of secondary metabolites on flow cytometry and Feulgen densitometry, and to see whether genome size variation has any systematic or phylogenetic significance. Using a range of cultivars, secondary compounds from corollas were shown to have only minor effects on the Feulgen method; the floral pigments were found to be relatively inert and seemed to have been extracted on fixation with acetic methanol. Freshly expanded corollas showed apparent apoptotic DNA decay in epidermal cells, so need to be used with caution. Flow cytometric measurements with propidium iodide in some cultivars resulted in a very similar average genome size (2C = 8.62 pg) as compared with Feulgen densitometry (2C = 8.84 pg). Leaf cytosol of D. variabilis has a demonstrable inhibitory effect on propidium iodide fluorescence, which may explain some of the intraspecific variation of C-values observed. DNA 2C-values ranged from 3.30 pg in D. dissecta (2n = 34) to 9.62 pg in a D. variabilis cultivar (2n = 64). The D. variabilis cultivars had broadly similar C-values showing a 1.16-fold range between cultivars. Some of this variation probably results from technical variables and the extent of genuine variation is uncertain. The highest 2Cx-value occurred in one D. coccinea accession (2.47 pg, 2n = 32; x = 8). D. coccinea with 2n = 64 showed slightly reduced Cx-values compared to D. coccinea with 2n = 32. Artificially produced interspecific hybrids had C-values that corresponded closely with expectations from the measured values obtained from their parents.     

Genome Size inAllium: In Quest of Reproducible Data

ComparingAlliumgenome size measurements of different authors,we noticed that the estimates for certain species diverge morestrongly than one would have expected in view of the methodologicaladvantages of the material. As the matter has theoretical significancefor explaining the biological role of genome size variation,we measured, by Feulgen densitometry, 28 species and altogether57 accessions or cultivars. Flow cytometric measurements supplementedthese data. The current hypothesis of a discontinuous and step-wisedistribution of DNA amounts inAlliumseems questionable, as mostof our DNA values did not appear in the corresponding DNA groupas proposed previously. On the other hand, we can confirm thatthere is a significant negative correlation between genome sizeof a species and its first month of flowering, but only in diploids,or in diploids and polyploids if only the basic genome size(2Cxlevel) is considered. We compared our results with thoseof nine other publications. Only 29 of 60 2C values publishedpreviously deviate less than 10% from our data, the others deviatemore strongly, from 0.44- to 1.44-fold. The more comprehensivedata sets of various authors were compared by correlation analysiswith our data. Positive and mostly significant correlationswere seen in all tests, but nevertheless the degree of incongruencebetween studies was unsatisfactory in view of the much betterintra-laboratory reproducibility of the present data. The presentwork highlights the need for generally agreed improvements instandardization and preparative procedures of cytophotometricgenome size determination.Copyright 1999 Annals of Botany Company Allium, genome size, Feulgen densitometry, flow cytometry, discontinuous DNA content variation, nucleotype hypothesis, flowering time, data reproducibility, correlation analysis.     

Cryptopolyploidy revisited: the case of Vinca (Apocynaceae)

This investigation presents a look back to ancient times of karyology with modern optical instruments. `Cryptopolyploidy', i.e. an intrinsically polyploid but numerically non-polyploid structure of chromosome complements, today is an obsolete concept of chromosome architecture and evolution, but was actively discussed up to the mid-seventies of the past century. We focus here at a hypothesis of cryptooctoploidy in Vinca difformis (2n = 46), which was based on a measured four-fold chromosome volume compared with V. minor (2n = 46), the proposed diploid. We used DNA flow cytometry and Feulgen densitometry to see, if the postulate of cryptooctoploidy in V. difformis in the retrospect could be justified. It was found not defendable, because V. difformis differed only about 1.55-fold in C-value from V. minor, which is far from a regular multiple and much less than the 4-fold. C-values are given also for V. major, V. herbacea and V. rosea.     

Nuclear DNA C-values Complete Familial Representation in Gymnosperms

The gymnosperms are a monophyletic yet diverse group of woodytrees with approx. 730 extant species in 17 families. A recentsurvey showed that DNA C-values were available for approx. 16%of species, but for only 12 of the 17 families. This paper completesfamilial representation reporting first C-values for the fiveremaining families: Boweniaceae, Stangeriaceae, Welwitschiaceae,Cephalotaxaceae and Sciadopityaceae. C-values for nine Ephedraand two Gnetum species are also reported. C-values are now availablefor 152 (21%) species. Analysis confirms that gymnosperms arecharacterized by larger C-values than angiosperms (modal 1Cof gymnosperms = 15.8 pg compared with 0.6 pg in angiosperms)although the range (1C = 2.25–32.20 pg) is smaller thanthat in angiosperms (1C = 0.05–127.4 pg). Given completefamilial coverage for C-values and increasing consensus in gymnospermphylogeny, the phylogenetic component of C-value variation wasalso investigated by comparing the two datasets. This analysisrevealed that ancestral gymnosperms (represented by cycads and/orGinkgo; mean genome size = 14.71 pg) probably had larger genomes thanancestral angiosperms. Copyright 2001 Annals of Botany Company Gymnosperm DNA amounts, C-values, phylogeny, ancestral genome size, Cycadales, Ginkgo, Gnetales, conifers, Pinaceae     

Genome size variation inCajanus cajan (Fabaceae): A reconsideration

A recent investigation of genome size in certain samples of the pigeonpea,Cajanus cajan, indicates values from 1.55 pg to 1.99 pg (1C level), which is 1.29-fold variation between accessions. In the present analysis those of these accessions which had particularly high or low DNA contents in that study were subjected to a reanalysis using propidium iodide and DAPI flow cytometry and Feulgen densitometry. Only minor differences in genome size, not more than 1.047-fold, were found with flow cytometry, and no significant differences were obtained with Feulgen densitometry. The previously reported genome size cannot be confirmed. It is about half as large and was determined in the present study as 0.825 pg (1C, propidium iodide flow cytometry,Glycine max as standard) and 0.853 pg (1C, Feulgen densitometry,Allium cepa andPisum sativum as standards), respectively.     

Evolution of DNA amounts across land plants (embryophyta)

BACKGROUND AND AIMS: DNA C-values in land plants (comprising bryophytes, lycophytes, monilophytes, gymnosperms and angiosperms) vary approximately 1000-fold from approx. 0.11 to 127.4 pg. To understand the evolutionary significance of this huge variation it is essential to evaluate the phylogenetic component. Recent increases in C-value data (e.g. Plant DNA C-values database; release 2.0, January 2003; http://www.rbgkew.org.uk/cval/homepage.html) together with improved consensus of relationships between and within land plant groups makes such an analysis timely. METHODS: Insights into the distribution of C-values in each group of land plants were gained by superimposing available C-value data (4119 angiosperms, 181 gymnosperms, 63 monilophytes, 4 lycophytes and 171 bryophytes) onto phylogenetic trees. To enable ancestral C-values to be reconstructed for clades within land plants, character-state mapping with parsimony and MacClade was also applied. KEY RESULTS AND CONCLUSIONS: Different land plant groups are characterized by different C-value profiles, distribution of C-values and ancestral C-values. For example, the large ( approximately 1000-fold) range yet strongly skewed distribution of C-values in angiosperms contrasts with the very narrow 12-fold range in bryophytes. Further, character-state mapping showed that the ancestral genome sizes of both angiosperms and bryophytes were reconstructed as very small (i.e. < or =1.4 pg) whereas gymnosperms and most branches of monilophytes were reconstructed with intermediate C-values (i.e. >3.5, <14.0 pg). More in-depth analyses provided evidence for several independent increases and decreases in C-values; for example, decreases in Gnetaceae (Gymnosperms) and heterosperous water ferns (monilophytes); increases in Santalales and some monocots (both angiosperms), Pinaceae, Sciadopityaceae and Cephalotaxaceae (Gymnosperms) and possibly in the Psilotaceae + Ophioglossaceae clade (monilophytes). Thus, in agreement with several focused studies within angiosperm families and genera showing that C-values may both increase and decrease, it is apparent that this dynamic pattern of genome size evolution is repeated on a broad scale across land plants.     

The dynamic ups and downs of genome size evolution in Brassicaceae

Crucifers (Brassicaceae, Cruciferae) are a large family comprisingsome 338 genera and c. 3,700 species. The family includes importantcrops as well as several model species in various fields ofplant research. This paper reports new genome size (GS) datafor more than 100 cruciferous species in addition to previouslypublished C-values (the DNA amount in the unreplicated gameticnuclei) to give a data set comprising 185 Brassicaceae taxa,including all but 1 of the 25 tribes currently recognized. Evolutionof GS was analyzed within a phylogenetic framework based ongene trees built from five data sets (matK, chs, adh, trnLF,and ITS). Despite the 16.2-fold variation across the family,most Brassicaceae species are characterized by very small genomeswith a mean 1C-value of 0.63 pg. The ancestral genome size (ancGS)for Brassicaceae was reconstructed as ^anc1C = 0.50 pg. Approximately50% of crucifer taxa analyzed showed a decrease in GS comparedwith the ancGS. The remaining species showed an increase inGS although this was generally moderate, with significant increasesin C-value found only in the tribes Anchonieae and Physarieae.Using statistical approaches to analyze GS, evolutionary gainsor losses in GS were seen to have accumulated disproportionatelyfaster within longer branches. However, we also found that GShas not changed substantially through time and most likely evolvespassively (i.e., a tempo that cannot be distinguished betweenneutral evolution and weak forms of selection). The data revealan apparent paradox between the narrow range of small GSs overlong evolutionary time periods despite evidence of dynamic genomicprocesses that have the potential to lead to genome obesity(e.g., transposable element amplification and polyploidy). Toresolve this, it is suggested that mechanisms to suppress amplificationand to eliminate amplified DNA must be active in Brassicaceaealthough their control and mode of operation are still poorlyunderstood.     

外来入侵植物和本地植物核DNA C-值的比较及其与入侵性的关系

用流式细胞仪测定了8科10属13种外来入侵植物、6种本地植物和1种外来非入侵植物的核DNAC-值。结果表明:作为整体,外来入侵植物的平均核DNAC-值显著低于本地种和外来非入侵种,但对同属不同类型植物进行比较,未发现一致的规律;在4个既包含外来入侵种又包含本地种的属中,泽兰属(Eupatorium)和鬼针草属(Bidens)外来入侵种的核DNAC-值显著低于同属本地种,莲子草属(Alternanthera)的2种外来入侵植物中仅有1个种的核DNAC-值显著低于同属本地种,而草胡椒属(Peperomia)外来入侵种的核DNAC-值显著高于同属本地种;表明核DNAC-值与外来植物入侵性无必然联系。     

Nuclear DNA amounts in Macaronesian angiosperms

Nuclear DNA contents for 104 Macaronesian angiosperms, with particular attention on Canary Islands endemics, were analysed using propidium iodide flow cytometry. Prime estimates for more than one-sixth of the whole Canarian endemic flora (including representatives of 11 endemic genera) were obtained. The resulting 1C DNA values ranged from 0.19 to 7.21 pg for Descurainia bourgeauana and Argyranthemum frutescens, respectively (about 38-fold difference). The majority of species, however, possessed (very) small genomes, with C-values <1.6 pg. The tendency towards small nuclear DNA contents and genome sizes was confirmed by comparing average values for Macaronesian and non-Macaronesian representatives of individual families, genera and major phylogenetic lineages. Our data support the hypothesis that the insular selection pressures in Macaronesia favour small C-values and genome sizes. Both positive and negative correlations between infrageneric nuclear DNA amount variation and environmental conditions on Tenerife were also found in several genera.     

First Nuclear DNA C-values for Another 25 Angiosperm Families

Nuclear DNA C-value is an important genomic biodiversity characterwith many uses. An international workshop sponsored by Annalsof Botany and held at the Royal Botanic Gardens, Kew, UK, in1997 identified major gaps in our knowledge of plant DNA C-valuesand recommended targets for new work. Improved taxonomic coveragewas highlighted as a key need for angiosperms, especially atthe familial level. In 1997 C-values were known for only approx.32% of angiosperm families; a goal of complete familial representationby 2002 was recommended. A review published in 2000 (Bennettet al.;Annals of Botany86: 859–909) noted poor progresstowards this aim: of the 691 first C-values for species only12 (1.7%) were for unrepresented families. We began new workto address this in 1999, reporting first DNA C-values for 25angiosperm families in 2001 (Hanson et al.;Annals of Botany87:251–258). Here we report first DNA C-values for a further25 angiosperm families, increasing familial coverage in angiospermsto approx. 45%. Such targeting remains essential to approachthe goal set by the 1997 workshop of familial coverage for angiospermswithin 5 years. The 4C DNA amounts presented here range from0.76 pg (similar toArabidopsis thaliana ) in Roridula gorgonias(Roridulaceae)to 29.74 pg in Gunnera manicata(Gunneraceae). 1C values were< 3.5 pg in 23 of the 25 families; these data provide furthersupport for the view that ancestral angiosperms almost certainlyhad small genomes (defined as 1C     

Nuclear DNA C-values in 30 species double the familial representation in pteridophytes

Nuclear DNA C-values and genome size are important biodiversity characters with fundamental biological significance. Yet C-value data for pteridophytes, a diverse group of vascular plants with approx. 9000 extant species, remain scarce. A recent survey by Bennett and Leitch (2001, Annals of Botany 87: 335-345) found that C-values were reported for only 48 pteridophyte species. To improve phylogenetic representation in this group and to check previously reported estimates, C-values for 30 taxa in 17 families were measured using flow cytometry for all but one species. This technique proved generally applicable, but the ease with which C-value data were generated varied greatly between materials. Comparing the new data with those previously published revealed several large discrepancies. After discounting doubtful data, C-values for 62 pteridophyte species remained acceptable for analysis. The present work has increased the number of such species' C-values by 93 %, and more than doubled the number of families represented (from 10 to 21). Analysis shows that pteridophyte C-values vary approx. 450-fold, from 0-16 pg in Selaginella kraussiana to 72.7 pg in Psilotum nudum var. gasa. Superimposing C-value data onto a robust phylogeny of pteridophytes suggests some possible trends in C-value evolution and highlights areas for future work.     

Nuclear DNA Amounts in Angiosperms

Bennett and Smith (Philosophical Transactions of the Royal Societyof London B274:227-274; B334: 309-345) and Bennett, Smith andHeslop-Harrison (Proceedings of the Royal Society of London,B216: 179-199) published lists of nuclear DNA amounts estimatedfor 1612 angiosperm species collected from 163 sources datedbetween 1951 and 1986. Subsequently, interest in genome sizein angiosperms and its significance has continued, and manynew DNA estimates were published during 1986-1994. Their inaccessibility,and the flow of enquiries for such information, shows that afurther compilation is needed. This paper presents a supplementarylist of nuclear DNA C-values for 105 sources for 899 angiospermspecies not listed in the above-mentioned compilations, plus284 additional estimates for 208 species already listed by them.The data are assembled primarily for reference purposes, withspecies listed in alphabetical order, rather than by any taxonomicscheme. Some advantages and limitations of flow cytometry, nowincreasingly used to quantify DNA C-values in plants, are reviewed.Recent reports regarding the occurrence and extent of intraspecificvariation in genome size are also discussed. While some examplesare real, others reflect technical shortcomings. Work has begunto combine the genome size data compiled in this and the above-mentionedpapers into a unified data base, and to present the informationin separate lists, with species in alphabetical and systematicorders, respectively. DNA C-values are now known for 1% of theworld's angiosperm flora, but improved representation of taxonomicgroups, geographical regions and plant life forms is urgentlyneeded.Copyright 1995, 1999 Academic Press Angiosperm DNA amounts, DNA C-values, nuclear genome sizes, intraspecific variation, flow cytometry, reference lists, genome size database     

Genome size variation in Arachis hypogaea and A. monticola re-evaluated.

Genome size variation within species is a frequently reported, but still a controversial problem. In the present study, we re-evaluated recently published Feulgen densitometric data on genome size and its infraspecific variation in Arachis hypogaea, and also conducted measurements in one accession of its wild relative A. monticola. The methods applied were propidium iodide flow cytometry and Feulgen densitometry using Pisum sativum as an internal standard. The 2C DNA contents previously published cannot be confirmed, but values obtained in this study are about half as large. Additionally, we could not reproduce the previously reported 1.15-fold variation within A. hypogaea; our data indicate genome size stability between respective accessions of this species. Based on 8.84 pg (2C) for Pisum sativum the DNA amounts (2C) were: 5.914 pg in A. hypogaea, and 5.979 pg in A. monticola.