Nuclear DNA Content Variation Within the Rosaceae

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E. E. Dickson Cornell University

K. Arumuganathan Cornell University

Stephen Kresovich University of South Carolina - Columbia, [email protected]

J. J. Doyle Cornell University

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Publication Info Published in American Journal of Botany, ed. Judy Jernstedt, Volume 79, Issue 9, 1992, pages 1081-1086. © American Journal of Botany 1992, Botanical Society of America.

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NUCLEAR DNA CONTENT VARIATION WITHIN THE ROSACEAE'

E. E. DICKSON,2,5 K. ARUMUGANATHAN,3 S. KRESOVICH,4 AND J. J. DOYLE2 2L. H. BaileyHortorium and 3Departmentof Plant Breeding and Biometry, CornellUniversity, Ithaca, New York 14853-4301;and 4USDA-ARSPlant Genetic Resources Unit, Cornell University, Geneva, New York 14456-0462

NuclearDNA contenthas beenestimated using flow cytometry for 17 speciesand eightcultivars of Malus and for44 speciesof 29 othergenera within the Rosaceae. Compared to otherangiosperms, diploid genome sizes vary little within the familyRosaceae and withinthe genus Malus. C-valuesof generawithin the subfamilies Spiraeoideae and Rosoideaeare amongthe smallest of flowering plants thus far reported. In general,the Maloideae have the largest diploid genomes of the family,consistent with their higher chromosome numbers and presumedpolyploid origin.

The Rosaceae, includingsuch economicallyimportant MATERIALS AND METHODS plants as almond, apple, strawberry,and rose, is consid- ered a naturalgroup held togetherby similaritiesin floral Leaf materialof rosaceous taxa was collectedfrom sev- structures.The foursubfamilies are definedby fruittype eral sources (Table 1). Voucher specimens are deposited (Robertson,1974), and each includespolyploid series with at theL. H. Bailey Hortorium(BH). Chromosome counts, fairlyconsistent chromosome base numbers:Spiraeoideae whereavailable, were gatheredfrom the literature(Table (x = 9); Amygdaloideae (x = 8); Rosoideae (x = 7, 8, and 2). 9); and Maloideae (x = 17) (Sax, 1931, 1932). The sub- For the determinationof nuclear DNA content,sus- familyMaloideae, with its relativelyhigh base chromo- pensions ofintact nuclei wereprepared from young leaves some number,has been hypothesizedto be eitherof au- by chopping(Galbraith et al., 1983) accordingto the pro- topolyploid (Darlington and Moffett, 1930) or cedure of Arumuganathanand Earle (1991la) and stained allopolyploid origin(Sax, 1931, 1932; Stebbins, 1950). withpropidium iodide. The isolation procedurewas fur- Althoughnumerous chromosome numbershave been ther modified for some members of the subfamilyRo- reportedfor Rosaceae, the amount of DNA per nucleus soideae bythe addition of 1% polyvinylpyrrolidone (PVP- (C-value) has been reportedfor only 14 species of the 40) to the initial isolation solution,without the addition family(Bennett and Smith, 1976, 1991; Bennett,Smith, of propidium iodide. The modifiedprocedure increased and Heslop-Harrison, 1982; Arumuganathanand Earle, the number of intact nuclei isolated. The mean fluores- 1991b). Apart from the utilityof genome size data in cence intensity,frequency, standard deviation, and coef- ongoingmolecular studies in thisimportant plant family, ficientof variation of the propidium iodide-stained nuclei the amount and distributionof nuclear DNA content at 488 nm were recordedwith an EPICS PROFILE flow variation among related taxa may give insightsinto ge- cytometer(Coulter Electronics, Hialeah, FL). Chicken nomic evolution that underlies or parallels speciation erythrocytes(2.33 pg DNA/2C; Galbraith et al., 1983) (Raina and Narayan, 1984; Ohri and Khoshoo, 1986; wereincluded with our samples as internalstandards (Fig. Price, 1988). 1). In this study,flow cytometry was used to estimatenu- The mean 2C-value of each sample was determinedby clear DNA contentsof 28 genera fromeach of the four multiplyingthe ratio of the fluorescencemeans of the Rosaceae subfamilies.Compared to Feulgen densitome- sample nuclei and chickenerythrocytes by the amount of try or reassociation kinetics,flow cytometryis a rapid DNA per chicken erythrocyte(2.33 pg). The standard and reliable method for estimatingC-values in plants deviation forthe mean 2C-value of each sample was cal- (Galbraith et al., 1983; De Laat, Gohde, and Vogelzang, culated by takinginto account the variances of the fluo- 1987; Raybum et al., 1989; Raybum, 1990; Michaelson rescencefrom both the sample and the internalstandard et al., 199 la). We here reportlow levels of nuclear DNA (W. Lamboy, personal communication): variationwithin the Rosaceae and findthat Spiraeoideae C-values are among the smallest of angiosperms.Rela- a2(samp/crbc) = U2(samp)/M(crbc)2 tivelylarge C-values of Maloideae supportthe polyploid + [U2(crbc) x M(samp)2]/M(crbc)4 originof the subfamily. Sample C-value standard deviation = o(samp/crbc) x 2.33 where I Receivedfor publication 25 November1991; revision accepted 27 April1992. (a2 = fluorescencevariance The authorsthank Steven Spongberg of theArnold Arboretum for M = fluorescencemean helpingin thecollection of leaf samples; Martha Rangel-Lugo for pro- samp = sample nuclei vidingchicken blood; and Kathy Anderson and Jim Slattery for assisting crbc = chicken erythrocytes in theoperation of the flow cytometer. 5 Authorfor correspondence. Our standard deviations are up to twice as large as for 1081 1082 AMERICAN JOURNAL OF BOTANY [Vol. 79 thosein whichwe assumedno variancefor the standard. TABLE 1. Originalsources and vouchersof plants used in thisstudy. reportsof C-value standarddeviations: 1) as- AA = Arnold Arboretum; CU = Cornell University;NY- Previous SAES = New YorkState Agricultural Experiment Station, Geneva, sumethe standard is constantwithout variance (Rothfels New York et al., 1966;Narayan, 1982; Price et al., 1983;Goldblatt, Walbot,and Zimmer,1984; Laurie and Bennett,1985; Spiraeoideae: Simsand Price,1985); 2) use a standardassuming a con- Exochordagiraldii, AA 1503-52A,EED 872. Neilliasimensis, AA stantmean and a constantstandard deviation (Galbraith 144-81,EED 875. Physocarpusbracteatus, AA 1235-85,EED 856; et al., 1983); or 3) give standarddeviations around the P. opulifolius,AA 1279-82-A,EED 857. Spiraeachinensis, AA 223- mean fluorescenceor mean densityof thesample in ar- 83, EED 855; S. crenata,AA 1230-85,EED 859; S. pubescens,AA bitraryunits (Chooi, 1971; Priceand Bachmann,1975; 541-83,EED 853; S. nipponica,CU, EED 900; S. sargentiana,AA Raybumet al., 1989; Raybum,1990; McMurphyand 1233-85,EED 854; S. wilsonii,AA 953-85-A,EED 852. Stephanan- Raybum,1991). dra incisa,CU, EED 902. Amygdaloideae: Osmaroniacerasiformis, AA 274-85,EED 879. Prinsepiauniflora, RESULTS AND DISCUSSION AA 7188-A,EED 848. Prunuspersica "Red Haven,"NYSAES, no voucher;P. serotina,NYSAES, EED 879; P. subhirtella,CU, EED The genomicDNA contentsof 44 rosaceousplants (29 903. genera),estimated from the mean fluorescence values of 500-2,000nuclei per sample,are listedin Table 2. The Rosoideae: ofvariation were less than 5% forall reported Dryasoctopetala, CU, EED 892.Duchesnea indica, Geneva, NY, EED coefficients 898. Neviusiaalabamensis, AA 1809-71,EED 873. Potentillafruc- samples.Previously obtained 2C-values of Rosaceae are ticosa,CU, EED 899. Rhodotypusscandens, AA 680-79,EED 851. includedin Table 2: six estimatedby Feulgenmicroden- Rosa multiflora,Geneva, NY, EED 897. Rubusodoratus, CU, EED sitometry(Bennett and Smith, 1976, 1991; Bennett, Smith, 896. and Heslop-Harrison,1982) and eightothers obtained by Maloideae: flowcytometry recently reported by one of us (Arugu- Amelanchiersp., NYSAES, EED 876. Aroniaarbutifolia, AA 1905- manathanand Earle, 1991b). The values obtainedby 81,EED 870. Chaenomelesspeciosa, NYSAES, EED 881. Cotoneaster Feulgendensitometry agree closely with the flowcyto- melanocarpa,Geneva, NY, EED 882. Crataeguscrus-galli, Geneva, metryvalues of other species within the same subfamily. NY, EED 883. Cydoniaoblonga, NYSAES, EED 877. Eriobotrya japonica,CU, no voucher.Malus spp.,NYSAES. Mespilusgerman- ofMalus x domestica ica, NYSAES, EED 878. Photineaparvifolia, AA 577-76,EED 867. Polyploidseries -The 2C-values Pyracanthacoccinea, CU, EED 901; P. sp. "Royal,"AA 194-49-A, and Prunus species correlatewith theirchromosome EED 869. Pyruscalleryana, CU, EED 895. Sorbusalnifolia, CU, EED counts.Malus x domesticaaccessions with chromosome 880; S. americana,NYSAES, EED 894. numbersof 2x, 3x, and 4x have 2C-values (standard deviation)of 1.55 (0.21), 2.51 (0.20), and 2.86 (0.43) pg, respectively,deviations from a perfectnumerical series well withinthe variationfound within apple (Table 3). genomewas reportedfor Cardamine amara L. (0.11 pg/ The 2C value of thediploid sweet cherry Prunus avium 2C) (Bennettand Smith,1991), another member of the (0.67 pg) is approximatelyhalf that of the tetraploid hy- Brassicaceae. bridcherry Prunus x sp. '4X' (1.36 pg). Othersmall C-values occur within the Rosaceae. Rosa In contrast,the nuclear DNA contentsof Spiraeapu- wichuraianaCrepin (Rosoideae) has a genomesize of0.2 bescensand S. nipponica,reportedly diploids, are two and pg/2C(Bennett and Smith,199 1). Withinthe Spiraeoide- fourtimes larger than the diploid genome of S. chinensis ae, severalwoody species of Spiraea and Physocarpus gave (Table 2). Becausepolyploidy is reportedin thisgenus, it fluorescencepeaks between 0.42 and 0.46 pg/2C(Table is reasonableto concludethat our accessionsof S. pu- 2) (Figs.2, 3). Outsidethe Brassicaceae and Rosaceae,a bescensand S. nipponicaare polyploids.Chromosome genomesmaller than these Spiraeoideae has onlybeen countsare necessary,however, to confirmpolyploidy for reportedfor Aesculus hippocastanum L. (0.3 pg/2C,Feul- theseSpiraea accessions.If theirchromosome numbers gen microdensitometry)(Bennett, Smith, and Heslop- arediploid, the 2C-value variation among diploid Spiraea Harrison,1982). However, we were unable to substantiate specieswould be remarkablylarge, with nearly as much thisvalue usingleaf tissuesampled from an A. hippo- variationas foundwithin the Rosaceae as a whole. castanumon theCornell campus (1.04 pg/2C;SD 0.05; flowcytometry). Diploid Rosaceae C-values are low among angio- The subfamilyAmygdaloideae also has relativelysmall sperms-Arabidopsisthaliana (L.) Heynh.(Brassicaceae) 2C-values(Table 2); however,Prunus diploid genomes, is widelyknown for its verysmall nuclear genome, with with2C valuesbetween 0.54 and 0.66 pg,are comparable estimatesof its 2C-value varying from 0.15 pg(Leutwiler, withthe genomes of other diploid angiosperms with small Hough-Evans,and Meyerowitz,1984), 0.30 pg (Aru- 2C-values,e.g., Urticaurens L. (Urticaceae)(0.6 pg/2C) muganathanand Earle, '1991a),to 0.4 pg (Bennettand and Lablab nigerMedik. (Fabaceae) (0.7 pg/2C)(Bennett Smith,1991) determinedby reassociationkinetics, flow and Smith,1976). cytometry,and Feulgenmicrodensitometry, respectively (discussedby Arumuganathanand Earle, 1991a). The Rosaceaediploid 2C-value variation -A rangein DNA discrepancyamong these reported 2C-values may be due contentamong diploid species of nearlyeightfold was to themultiple ploidy levels in Arabidopsisthaliana (Fig. detectedamong 28 generaof the four Rosaceae subfam- 1) (Arumuganathanand Earle, 1991 a; Galbraith,Harkins, ilies(Fig. 4). The rangeof C-values reported for a family and Knapp, 1991). Recently,an even smallernuclear is meaningfulonly if samplingof taxa is extensive.Al- September 1992] DICKSON ET AL.-ROSACEAE DNA CONTENT 1083

TABLE 2. Mean 2C-values,standard deviations (SD), andploidy levels of Rosaceae species with citations of source and ploidy reference

2C (pg) SD Sourcea Ploidy PloidyrefP Spiraeoideae x = 9 Physocarpusopulifolius (L.) Maxim. 0.42 0.09 1 2x 6 Spiraeachinensis Maxim. 0.42 0.11 1 Physocarpusbracteatus (Rydb.) Rehd. 0.43 0.07 1 Spiraea crenata L. 0.46 0.10 1 Stephanandra incisa (Thunb.) Zabel 0.53 0.06 1 Neillia simensis D. Oliver 0.54 0.08 1 2x 3 Spiraea pubescens Turcz. 0.94 0.11 1 2x 7 Exochordagiraldii Hesse. x = 8 1.11 0.19 1 2x 7 Spiraea wilsoniiDuthie 1.59 0.15 1 Spiraea nipponica Maxim. 1.75 0.13 1 2x 7 Spiraea sargentiana Rehd. 1.84 0.11 1 Amygdaloideae x = 8 Prunuspersica (L.) Batch. "Madison" 0.54 0.05 3 2x 7 Prunuspersica (L.) Batch. "Red Haven" 0.55 0.06 1 2x 7 Prunus armenaica L. "Sundrop" 0.60 0.06 3 2x 7 Prunus subhirtellaMiq. 0.60 0.09 1 2x 7 Prunus avium (L.) L. "Van" 0.67 0.06 3 2x 5 Osmaroniacerasiformis x = 6 0.98 0.11 1 2x 6 (Torr. & Gray ex Hook. & Am.) Greene Prunus serotinaJ.F. Ehrh. 1.00 0.13 1 4x; 5x, 6x 3 Prunus x spp. "4X" 1.36 0.12 3 4x Prunus cerasus L. "Montmorency" 1.42 0.08 3 4x 2 Prunusx spp. "Standley" 1.83 0.07 3 6x Prinsepia unifloraBatal. 3.09 0.28 1 4x 7 Rosoideae Rosa wichuraianaCrepin x = 7 0.2 2 2x Rubusidaeus L.x=7 0.58 0.10 3 2x;4x 1 Rosa blandaAiton x = 7 0.6 2 3x Acaena magellanica (Lam.) Vahl. x 7 0.6 4 6x 2 Potentillafructicosa L. 0.80 0.70 1 2x; 4x; 6x 8 Rhodotypusscandens (Thunb.) Mak. x = 9 0.74 0.10 1 2x 7 Rubus odoratusL. x= 7 0.76 0.22 1 2x 8 Neviusiaalabamensis A. Gray x = 9 1.02 0.11 1 2x 6 Sanguisorbaminor Scop. x = 7 1.1 2 4x Aphanes arvensisL. x =8 1.1 5 6x 7 Dryasoctopetala L. x= 9 1.16 0.25 1 2x 1 Rosa acicularisLindley x = 7 1.3 2 6x Rosa multifloraThunb. ex J. Murr. x = 7 1.65 0.11 1 2x; 4x 1 Duchesnea indica (Andr.) Focke x = 7 3.00 0.14 1 6x; 12x 8 Maloideae x = 17 Pyracantha"Royal" 0.99 0.16 1 Pyruscommunis L. "Bartlett" 1.11 0.06 3 2x 7 Chaenomeles speciosa (Sweet) Nakai 1.20 0.16 1 2x 7 Pyruscalleryana Decne. 1.26 0.29 1 2x 7 Amelanchiersp. 1.31 0.25 1 Sorbus alnifolia (Siebold & Zucc.) Koch 1.36 0.32 1 2x 7 Sorbus americana Marsh 1.30 0.37 1 2x 7 Pyracantha coccinea E. J. Roem. 1.41 0.31 1 2x 7 Cydonia oblonga Mill. 1.45 0.14 1 2x 1 Mespilus germanica L. 1.48 0.15 1 2x 3 Eriobotryajaponica (Thunb.) Lindl. 1.54 0.17 1 2x 1 Cotoneastermelanocarpa Lodd. 2.24 0.20 1 4x 4 Photinea parvifolia(E. Pritz.) Schneid. 2.29 0.26 1 Aronia arbutifolia(L.) Pers. 2.57 0.20 1 2x; 4x 7 Crataegus crus-galliL. 2.71 0.24 1 3x; 4x 7 a Source: 1 = this paper; 2 = Bennettand Smith, 1991; 3 = Arumuganathanand Earle, 1991b; 4 = Bennett,Smith, and Heslop-Harrison, 1982; 5 = Bennettand Smith, 1976. b Ploidy reference:1 = Index to plant chromosome numbers 1984-1985. (Peter Goldblatt,ed. 1988. Monographs in SystematicBotany from the Missouri Botanical Garden 23.) 2 = Index to plant chromosomenumbers 1982-1983. (Peter Goldblatt,ed. 1985. Monographsin SystematicBotany fromthe Missouri Botanical Garden 1 3.) 3 = Indexto plantchromosome numbers 1972. (R. J.Moore, ed. 1974. RegnumVegetabile 91.) 4-=Index to plantchromosome numbers 1967-1971. (R. J. Moore,ed. 1973.Regnum Vegetabile 90.) 5-=Index to plantchromjosome numbers 1966. (R. Omnduff,ed. 1968.Regnum Vegetabile 55.) 6-=Index to plantchromosome numbers 1958-1960. (1- and Supplement.)(M. S. Cave,ed. UFniversity ofNorth Carolina Press, Chapel Hill, NC.) 7 = Chromosomeatlas of flowering plants. (C. D. Darlingtonand A. P. Wylie,1955. George Allen and Unwin,London.) 8 = Chromosomenumbers of flowering plants. (Z. Bolkovskikh,V. Grif,T. Matejeva,and 0. Zakharyeva,eds. 1969.Izdatel'stvo Nauka,Leningrad.) 1084 AMERICAN JOURNAL OF BOTANY [Vol. 79

TABLE 3. Mean C-values and standarddeviations ofMalus speciesand cultivars.Samples of Malus species werecollectedfrom trees grown - 300 Arabidopsis thusana 4C ,8C 1 at the USDA -ARS Plant GeneticResources Unit,Geneva, New York zo50

pg/2C SD o 2C M. angustifolia(Aiton) Michaux GMALa-2347 1.46 0.08 ;.4 101 M. baccata (L.) Borkh. GMAL-0434 1.61 0.30 i=oo- ii 16C M. coronaria (L.) Mill. GMAL-2906 (3x) 2.23 0.07 50~~~~~~~~~~6 M. coronaria (L.) Mill. GMAL-3064 (4x) 3.11 0.13 60 M. florentina(Zuccagni) Schneid. GMAL- 1546 1.63 0.23 M. formosana Kaw. & Koidz. GMAL-2726 1.23 0.30 0 32 64 96 128 160 192 304 256 M. fusca (Raf.) Schneid. GMAL-1234 1.54 0.26 M. honanensisRehd. GMAL-2721 1.33 0.23 *H100 M. hupehensis(Pamp.) Rehd. GMAL-1022 (3x) 2.30 0.24 -% Spunea crenata - C 2 M. ioensis (A. Wood) Britt.GMAL-2941 1.55 0.10 ~75 / M. kansuensis(Batal.) Schneid. GMAL- 1840 1.33 0.25 M. prunifolia(Willd.) Borkh. GMAL-1069 1.63 0.27 M. pumila Mill. GMAL- 1061 1.67 0.21 50 M. sargentiiRehd. GMAL-0539 (3x, 4x) 1.97 0.23 M. trilobata(Labill.) Schneid. GMAL- 1836 1.63 0.25 zo 10 M. tschonskii(Maxim.) Schneid. GMAL- 1834 1.21 0.24 M. transitoria(Batal.) Schneid. GMAL-1822 1.51 0.30 M. yunnanensis(Franch.) Schneid. GMAL- 1819 1.39 0.16 0 32 64 96 130 192 304 M. x domestica Borkh. 160 256 "0523" GMAL-0523 1.50 0.29 "Liberty" GMAL-0824 1.55 0.21 CRBC 3 "Bedford" 1.56 0.25 Spiraea 2C "Prima" GMAL-1064 1.59 0.29 "Prince George" 1.64 0.24 "Spartan" GMAL-1247 1.73 0.33 "Jonagold" GMAL-0619 (3x) 2.51 0.20 Arabidopsis 2C "E8" (4x) ' 8 2.86 0.43 ~100 4C j6C a GMAL refersto thecatalog numberfor Malus at theNational Germ- plasm Repositoryfor Apple and Grape, Geneva, NY. zo 0 30 64 96f m 160 192 304 256 Relative fluorescence thoughlittle is known about C-value variation in many Figs. 1-3. Numbers of nuclei as a functionof fluorescenceintensity angiospermfamilies, five- to tenfolddifferences among (log scale). 1. Arabidopsisthaliana. The multiplepeaks correspond to diploids are found withinother floweringplant families multipleploidy levels of nuclei withina singleplant's leaves. 2. Spiraea with up to 30-fold ranges in 19 genera (30 species) of crenata.3. Arabidopsisthaliana, Spiraea crenata,and chickenred blood cells (CRBC) combined. Iridaceae (Goldblatt, Walbot, and Zimmer, 1984), 40- foldin twogenera (seven species) ofDroseraceae (Rothfels and Heimburger, 1968), and 80-fold in six genera (22 eralspecies of Malus (threespecies of Malus sectionChlo- species) of Ranunculaceae (Rothfelset al., 1966). With romeles;Dickson, unpublished data), the 2C variation thevery recent publication of the extremely small C-value (lessthan 2%) is lowerthan that between species of Malus. of Rosa wichuraiana(Bennett and Smith,1991) (Table 2), In comparison,C-values of inbredlines of Helianthus the rangeof knownRosaceae C-values has been doubled. annuushave as muchas 32% variation(Michaelson, et Nevertheless,compared to thatof otherangiosperm fam- al., 1991b). ilies, Rosaceae C-value variation is low, even including the Maloideae whichis thoughtto be of polyploid origin. Evolutionof theMaloideae-The relativelyhigh chro- Because 2C-value variation withinthe familyis rela- mosomenumber of the Maloideae (x = 17) suggestedto tivelylow, we did not expectto findmuch variation within earlyworkers that the subfamily had a polyploidorigin. genera or species. 2C values of 17 diploid Malus species, Controversiesarose, however, concerning whether 7, 8, includingrepresentatives from the fivesections of Huck- or 9 was theprogenitor chromosome base numberof an ins (1972) (Table 3), ranged only from 1.21 to 1.67 pg. autopolyploidMaloideae, and later,whether the subfam- In contrastto this rathersmall rangeof variation,Laurie ily was allopolyploid(Nebel, 1929; Tishler,1929; Dar- and Bennett (1985) found about twofold differencesin lingtonand Moffett,1930; Sax, 1931). Isozymestudies nuclear DNA contentsamong diploid Zea species, while ofMalus showduplicated gene systems indicative ofpoly- threefolddifferences in DNA contenthave been reported ploidy,and allelesegregations and fixedheterozygosities among diploid Microserisspecies (Price and Bachmann, suggestiveof allopolyploidy(Chevreau, Lespinasse, and 1975), fourfoldin Helianthus and Anemone (Sims and Gallet,1985; Chevreauand Laurens,1987; Weedenand Price, 1985; Rothfelset al., 1966), fivefoldin Vicia (Raina Lamb, 1987; Dickson,Kresovich, and Weeden,1991). and Narayan, 1984), and ninefoldin Crepis (Jones and The meioticbehavior of triploidapple convincedSax Brown, 1976). (1932) thatthe Maloideae arosefollowing hybridization C-values of diploid M. x domestica cultivars ranged betweenancestors within the Rosaceae havingx = 8 and from1.50 to 1.73 pg/2C (Table 3). Similarly,within sev- x = 9. Stebbins(1950) arguedon morphologicalgrounds September 1992] DICKSON ET AL.-ROSACEAE DNA CONTENT 1085

X = 0.56 the evolutionaryorigins of the subfamilyMaloideae. Preslia 53: Spiraeoideae 289-304. CHEVREAU,E., AND F. LAURENS. 1987. The patternof inheritance in apple (Malus x domesticaBorkh.): further results from leaf isozyme analysis. Theoreticaland Applied Genetics75: 90-95. , Y. LESPINASSE, AND M. GALLET. 1985. Inheritanceof pollen enzymes and polyploid origin of apple. Theoretical and Applied X = 0.66 Amygdaloideae Genetics71: 268-277. CHOOI, W. Y. 1971. Variation in nuclear DNA contentin the genus Vicia. Genetics68: 195-21 1. DARLINGTON, C. D., AND A. A. MoFFETT. 1930. Primaryand secondary chromosome balance in Pyrus.Journal of Genetics22: 129-151. , AND A. P. WYLIE. 1955. Chromosomeatlas of flowering plants, 2d ed. George Allen and Unwin, London. Rosoideae X = 0.66 DE LAAT, A. M., W. GOHDE, AND M. J. D. C. VOGELZANG. 1987. Determinationof ploidy of singleplants and plant populations by flowcytometry. Plant Breeding99: 303-307. DICKSON,E. E., S. KRESOVICH, AND N. F. WEEDEN. 1991. Isozymesin 1= .46 North American Malus (Rosaceae): hybridizationand species dif- ferentiation.Systematic Botany 16: 363-375. Maloideae GALBRAITH, D. W., K. R. HARKINs, AND S. KNAPP. 1991. Systematic endopolyploidyin Arabidopsisthaliana. Plant Physiology96: 985- 989. 1 , J. M. MADDox, N. M. AYREs,D. P. SHARMA, AND E. 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 FIRoozABoDY. 1983. Rapid flow cytometricanalysis of the cell cycle in intactplant tissues. Science 220: 1049-1051. Fig. 4. Distributionand mean (arrows) 2C-values of diploid plants GOLDBLATT, P., V. WALBOT, AND E. A. ZIMMER. 1984. Estimationof of Rosaceae subfamilies(from Table 1). genome size (C-value) in Iridaceae by cytophotometry.Annals of the Missouri Botanical Garden 71: 176-180. (x = 8) and a primitivespi- HucKINs, C. A. 1972. A revision of the sections of the genus Malus that a primitiveamygdaloid NY. = More recentmor- Miller. Ph.D. dissertation,Cornell University.Ithaca, raeoid (x 9) were the likelyparents. JoNEs,R. N., AND L. M. BROWN. 1976. Chromosome evolution and phological (Phipps et al., 1991) and chemical (Challice, DNA variation in Crepis. Heredity36: 91-104. 1974, 1981) data supportthis view. LAURIE, D., AND M. D. BENNETT. 1985. NuclearDNA contentin the Diploid nuclear DNA contents of the four Rosaceae genera Zea and Sorghum. Intergeneric,interspecific and intraspe- subfamiliesoverlap in value, and subfamilyC-value means cificvariation. Heredity55: 307-313. withchromosome numbers. However, LEUTWILER, L. S., B. R. HOUGH-EvANs,AND E. M. MEYEROWITZ. 1984. are not correlated The DNA ofArabidopsis thaliana. Molecular and General Genetics the DNA contentswithin the Maloideae are broadlycon- 194: 15-23. sistentwith a polyploid originof the subfamily(Table 1; McMu1UHY, L. M., AND A. L. RAYBuRN. 1991. Lack of relationship Fig. 4). Diploid Maloideae values correspondto the sum between relativematurity and genome size in hybridmaize. Crop of two diploid genomes fromany of the othersubfamilies Science 31: 63-67. that could be the result of either an autopolyploid or MICHAELSON, M. J., H. J. PRICE, J. R. ELLISON, AND J. S. SPENCER. of Assuming allopoly- 1991a. Comparison of plantDNA contentsdetermined by Feulgen allopolyploid doubling genomes. microspectrophotometryand laser flowcytometry. American Jour- ploidy, C-value data cannot resolve whetheran originat- nal of Botany 78: 183-188. ing hybridizationoccurred between genera or species 1 ~~, J. S. JOHNSTON, AND J. R. ELLISON. 1991b. Variation withinthe same or fromdifferent subfamilies. Therefore, of nuclear DNA contentin Helianthus annuus (Asteraceae). Amer- none of the othersubfamilies can be excluded as possible ican Journalof Botany 78: 1238-1243. ancestorsof the Maloideae based on nuclearDNA content NARAYAN, R. K. J. 1982. Discontinuous DNA variation in the evo- alone. lution of plant species: the genus Lathyrus.Evolution 36: 877-891. NEBEL, B. 1929. Zur cytologievon Malus II. Zuchter 1: 215-217. OHRI, D., AND T. N. KHOSHOO. 1986. Plant DNA: contentsand sys- LITERATURE CITED tematics.In S. K. Dutta [ed.], DNA systematics,vol. 2: Plants, 1- 19. CRC Press, Boca Raton, FL. ARUMUGANATHAN,K., ANDE. D. EARLE. 1991a. Estimationof nuclear PHIPPS, J. B., K. R. ROBERTSON, J. R. ROHRER, AND P. G. SMITH. 1991. DNA contentof plants by flow cytometry. Plant Molecular Biology Originsand evolutionof subfam.Maloideae (Rosaceae). Systematic Reporter9: 229-241. Botany 16: 303-332. , AND . 199lb. NuclearDNA contentof some important PRICE, H. J. 1988. Nuclear DNA contentvariation within angiosperm plantspecies. Molecular Biology Reporter 9: 208-218. species. EvolutionaryTrends in Plants 2: 53-60. BENNETT, M. D., AND J. B. SMITH. 1976. NuclearDNA amountsinI , AND K. BACHMANN. 1975. DNA contentand evolution in the angiosperms.Philosophical Transactions of theRoyal Societyof Microseridinae.American Journal of Botany 62: 262-267. LondonB 274: 227-274. , K. L. CHAMBERS, K. BACHMANN, AND J.RicGs. 1983. Inher- , AND . 1991. NuclearDNA amountsin angiosperms. itance of nuclear 2C DNA contentvariation in intraspecificand PhilosophicalTransactions of the Royal Sociey of London B 334: interspecifichybrids of Microseris(Asteraceae). AmericanJournal 309-345. of Botany 70: 1133-1138. , AND J. S. HEsLoP-HARRISON. 1982. NuclearDNA RAINA, S., AND R. K. NARAYAN. 1984. Changes in DNA composition amountsin angiosperms. Proceedings ofthe Royal Society ofLondon in the evolution of Vicia species. Theoreticaland Applied Genetics B 216: 179-199. 68: 187-192. CHALLICE, J. S. 1974. Rosaceae chemotaxonomyand the originsof RAYBURN, A. L. 1990. Genome size variationin southwesternUnited thePomoideae. Journalof the Linnean Society of London, Botany StatesIndian maize adaptedto variousaltitudes. Evolutionary Trends 69: 239-259. in Plants 4: 53-57. 1981. Chemotaxonomicstudies in thefamily Rosaceae and , J. A. AUGER, E. A. BENZINGER, AND A. G. HEPBURN. 1989. 1086 AMERICAN JOURNAL OF BOTANY [Vol. 79

Detection of intraspecificDNA contentvariation in Zea mays ssp. SIMs, L., AND H. J. PRICE. 1985. NuclearDNA contentvariation in maysby flowcytometry. Experimental Botany 40: 1179-1183. Helianthus(Asteraceae). American Journal of Botany72: 1213- ROBERTSON, K. R. 1974. The generaofthe Rosaceae in thesoutheastern 1219. UnitedStates. Journal of the Arnold Arboretum 55: 303-662. STEBBINS, G. L. 1950. Variationand evolutionin floweringplants. ROTHFELS, K., AND M. HEIMBURGER. 1968. Chromosomesize and ColumbiaUniversity Press, New York,NY. DNA values in sundews (Droseraceae). Chromosoma 25: 96-103. TISHLER, G. 1929. Verknupfungsversuchevon Zytologie und Syste- , E. SEXSMITH, M. HEIMBURGER, AND M. KRAUSE. 1966. Chro- matikbei den Blutenpflanzen.Berichte der Deutschen Botanischen mosome size and DNA contentof species ofAnemoneL. and related Gesellschaft47: 30-49. genera (Ranunculaceae). Chromosoma 20: 54-74. WEEDEN, N. F., AND R. C. LAMB. 1987. Geneticsand linkageanalysis SAx, K. 1931. The originand relationshipsof the Pomoideae. Journal of 19 isozymeloci in apple. Journalof theAmerican Society of ofthe Arnold Arboretum 12: 3-22. HorticulturalScience 1 12: 865-872. 1932. The originof the Pomoideae. Proceedingsof theAmer- ican HorticulturalSociety 30: 147-150.

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The cover photographon theJune 1992 American Journal of Botany was printedupside down. The species listed for top and bottom rows should be reversedin the caption forthe cover illustrationat the top of the Contentspage in that issue.