Chapter 5 Genetic Analysis of Apomixis - cimmyt

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14 JoG.. B.rth""dTable 2.8 Distribution of clones according to ploidylevel from the P. maximum collection established inCote d'ivoire (Combes 1975)Total 2x 3x* 4x 5x** 6x**551 19 0 506 12 13• 3x ploidy level not found in wild populations•• 5x and 6x overrepresenled in Ihis collection (from over·collecting inthese populotions)Table 2.8 shows the distribution of clonesaccording to their ploidy level in a collectionestablished in Cote d'Ivoire.Triploid plants have been experimentallyobtained from hexaploids (n + 0 progeny) aswell as from diploid x tetraploid crosses.(Poly-) haploids also have beenexperimentally obtained from tetraploids,and the resultant plants have been eithersexual or sterile (potentially apomictic asshown by embryo sac analyses). Thesefindings led Savidan and Pernes (1982) topropose an evolutionary scheme based onploidy cycles involving di-tetra-haploid levelsas in the Dichanthium complex. The changefrom diploid to tetraploid is realized through2n + n hybridization with pollen fromtetraploid plants. In this system, sexuality ismaintained at the diploid level. Contactbetween diploid and tetraploid plants allowsgenetic exchange between these pools(compartments) and creation of sexualtetraploid plants, allowing the release of newgenetic diversity at the tetraploid level.Paspalum Agamic Complex (Poaceae)The center of diversity for the genus Paspalumis in South America. Studies conducted byQuarin (1992), Norrman et al. (1989) andcollaborators at the Instituto de Botanica delNordeste, Corrientes, Argentina (IBONE)show that many species in this genus havegenetic pools at two or more ploidy levels(Table 2.9).ln the pool with the lowest ploidylevel, plants are sexual and self-incompatible,while in pools with higher ploidy levels, theyare apomictic and self-compatible. In manycases, the two pools are at the diploid andtetraploid level (group 3 ofTable 2.9). In somespecies, however, the sexually selfincompatibleplants are tetraploid and the selfcompatibleapomictic plants are hexaploid oroctoploid (group 6 ofTable 2.9).Some species that are sexual and selfcompatibleat the tetraploid or hexaploid level(groups 5 and 7 of Table 2.9) are not apomicticat higher ploidy levels. In other species,triploids are often apomictic and are found inspecies with sexual diploids and apomictictetraploids.As with previously cited agamic complexes,sexual forms are found at the lowest ploidylevel and apomictic forms at the other levels.However, in this example, the relationshipincludes the incompatibility system.Apomictic plants are self-eompatible and thecorresponding sexual plants are selfincompatible.Experiments should beconducted to determine whether this alsooccurs in other agamic complexes.Tripsacum Agamic Complex (Poaceae)The Tripsacum genus is restricted to the NewWorld, from 42°N to 240$. Its center ofdiversity(or origin) is located in Mexico and Guatemala,and 11 of the 16 species described for the genusare found in this region. These 11 species showdifferent ploidy levels both within and amongthemselves. The collection the team assembledfrom Mexico displayed the followingdistribution (unit = one ploidy level of onespecies in one population): diploids, 16.4%;triploids, 7.9%; tetraploids, 72%; penta- andhexaploids, 3.7%.When compared to other agamic complexes,a high frequency of triploid plants in theTripsawm complex was observed. These wildtriploid plants are apomictic, produce fertilepollen, and set good seed. All of the naturalpolyploids we observed were apomictic(Leblanc et al. 1995; and unpublished data).
ApOmil~ cnd !lo. Mcacgemeot 01 Gnetk Diversity 15Diploids are sexual, and progeny with 211 + 11chromosomes from apomictic plants occur ata significant frequency (Tables 2.4 and 2.5).Through this mechanism, many hexaploidswere produced experimentally or detected inseeds collected from a wild population.Natural hexaploid plants in wild populationswere observed at a lower frequency than inthe seed progeny we analyzed.residual sexuality exists in apomicts, whichpermits production of 11 + /1 progeny. Thissexuality favors creation of new diversity atthe tetraploid level by allowing crossesbetween apomictic plants.Our model (Figure 2.2) suggests that in theTripsaCllrn agamic complex, sexuality fosterstwo stages: (i) a change from tetraploidy toTriploid plants can be obtainedin four ways: (i) from 211 + 11hybridization within diploids,(ii) from crosses betweendiploid and tetraploid plants,(iii) from haploidization ofhexaploids (/1 + aprogeny), or(iv) from asexual propagationof apomictic triploids.Evaluation of these possibilitiesis currently underway.In addition we have observedthe presence of triploids,tetraploids, and hexaploids,and absence of diploids insome wild populations, whichsuggests that some triploidscould have originated fromhaploidization of hexaploidplants. In populationscontaining diploids andtriploids, there is a possibilityof 2/1 + n hybridization, with2/1 from the triploid femaleand 11 from a diploid maleleading to the production ofnew tetraploid plants. Wehave documented such anevent in seeds from one wildpopulation. This event showsone possible route of geneexchange from the diploid tothe tetraploid genetic pool. Wedid not discover any sexualtetraploid TripsaCLlm, butTable 2.9 Distribution of species of Paspalum according to theirincompatibility system, ploidy level, and meiosis behavior (fromstudies at IBONE, Quarin, personal comm.)Species 2x 3x 4x Sx 6x 8xolmum sex, SI+ opo, SC*berlonii sex, SI+ opo, SC*brunneum sex, SI+ opo, SC*compressifolium sex, SI+ opo, SC* opo, SC*coryphoeum sex, SI+ opo, SC*cromyorrhizon sex, SI+ opo, SC*dedeccoe sex, SI+ opo, SC*denliculolum sex, SI+ opo, SC*dislichum sex, SI+ opo, SC* opo, SC*equilons sex, 51+ opo, SC*houmonii sex, 51+ opo, SC*hydrophilum sex, SI+ opo, SC* opo, SC*indecorum sex, 51+ opo, SC*inlermedium sex, 51+ opo, SC* opo, SC*moculosum sex, SI+ opo, SC*modestum sex, SI+ opo, SC*nololum sex, 51+ opo, SC* opo, SC*poluslre sex, 51+ opo,SCprocurrens sex, SI+ opo, SC*proliferum sex, SI+ opo, SC*quodrilorium sex, SI+ opo, SC* opo, SC*rulum sex, 51+ opo, SC*simplex sex, 51+ opo, SC*boscionumsex, SC+dosypleurumsex, SC+dilololum sex, SC+ opo, SC·regnelliisex, SC+virga tumsex, SC+durilolium sex, SI+ opo, SC*ionolhum sex, SI+ opo, SC*conspersumsex, SC+inoequivolvesex, SC+loxumsex, SC+romboisex, SC+lex =lexual mode of reproduction; apo =opomictic mode of reproduction; SC =lelf compotible;51 =lelf incompotible; +=meiolil regulor; • =mei~il irregulor; -=meiolis with monyunivalentl
Page 2 and 3: (over illustration:Pictured is an i
Page 4 and 5: Institut de Recherche pour Ie Devel
Page 6 and 7: iv33 Outlook33 References35 Appendi
Page 8 and 9: vi131 Screening Procedures: Advanta
Page 10 and 11: VIIITables4 Table 1.15 Table 1.29 T
Page 12 and 13: xAcknowledgmentsWe are grateful to
Page 14 and 15: xiifood crops such as maize, wheat,
Page 16 and 17: 2 Gary H. T....i.....much food as i
Page 18 and 19: 4 Gary H. Toe"'...breeding: the evo
Page 20 and 21: 6 Gary H. T....it....The potential
Page 22 and 23: Chapter 2Apomixis and the Managemen
Page 24 and 25: 10M.. Be,th.dcategories n + nand 2n
Page 26 and 27: 12 J.&eo BertIoaodtwo tetraploid sp
Page 30 and 31: 16 M......thodhexaploidy through 2n
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Page 34 and 35: 20 JM Iertltaodmarkers to retain th
Page 36 and 37: 22 JoA•• BerthudFurthermore, if
Page 38 and 39: Chapter 3Classification of Apomicti
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Page 42 and 43: simultaneous division of the proxim
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Page 58 and 59: Chapter 4Ultrastructural Analysis o
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Page 62 and 63: (Figure 4.2a,b,c). Their cytoplasm
Page 64 and 65: 50 Tomaro N. Naurnovo ond Jeon-Phil
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Page 68 and 69: 54 Tamara N. Nauma.a and J...-Phaip
Page 70 and 71: 56 Tamara H. Haumaya ...d J...-Phmp
Page 72 and 73: 58 Tamara N. N....... Old JOGO-PUIp
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Page 76 and 77: 62 Tamara N. Nouma.o and Jeon-Phmpp
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Chapter 5Genetic Analysis of Apomix
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66 Robe" T. SherwoodIn mitotic dipl
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68 ••It T. Sllorwoodmegasporoge
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70 Robert T. SherwoodIdentification
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72 R....11 T. SlMrwoodwe postulate
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74 Rob.rt T. Sherwoodin the gametop
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76 Rokrt T. SHtwoodPerhaps the most
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78 Robe" T. S~erwoodEnvironment pla
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80 Robert T. SherwoodBanaglio, E. 1
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82 Robe" 1. Sherwood---. 1989. Apom
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84 Dcaitl ~11i-, lot To...., .od Di
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86 Do.lel Griome/I-, Joe To~ ....,
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88 Oaoitl G
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90 o.lel ~II-, Jo. lob.., aod Diego
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and meiotic or developmental mutant
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94 D..iel Grimallelli-, Jo. Tohme,
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96 10k. G.(o,.,..mechanisms (Figure
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98 Jolo.G.(_explain the existence o
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100 JolI.G.C....parameters affectin
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102 1010. G.(arma.was developed in
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104 J... G.(.....effects), which co
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106 J.hG.eforseveral thousand to a
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108 Jelo.G.(_large linkage group in
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11 0 Joh. G.(orma.---. 1997. Asynch
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112 a... A. 8icUeI1993). Before the
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114 ROil A. 8idlooll(Sherwood et al
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116 R... A. IkbeIlinduced mutation
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118 Ron A. Mlltllstudies of apomixi
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120 I... A. BkbollLeblanc, 0., M.D.
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122 Olivier L.bla.,.ncI A.d,ea M.nu
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124 Olivier lt~1ao< aod Aock.. Mau"
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126 OIlrier Ltblaooc ood AocI...Mo,
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128 or..Ie, leblal( allll Aodrea Ma
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130 Ofjyier LH......AodrH Mom","Mar
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132 Olivier leblaoc and Aldr.. Mall
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134 OIivie' I
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136 or..io. u.~100< awd Aod.... M.n
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138 udda lorge. do Val. aod Joh W.
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140 Ca
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142 C«ida Jorge. do Va" aod Jah W.
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144 (..iIda 80rges cit Va" DOd Ja~.
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146 Cacido ....... Vole..J.b W. MIe
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148 Ca
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150 (adlda Borge. da VaNe and Joh.
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152 Ccdda Borge. do v..... J.h W. M
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154 Yve< 5
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156 rn. s.mdaosearch for an opitimu
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158 Yv•• Savid..unreduced polar
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160 Yves SoviclaoBashawet al. (1970
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162 hOI Scrvidao211 = 56 chromosome
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164 r.., SaYid..Transfer of Gene(s)
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166 rves Sqyldaounanswered. However
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Chapter 12From Sexuality to Apomixi
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170 lie. Gros..iklalSgametes and em
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172 Uti Gro....1aosGunning 1990). T
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174 UeIGr.........embryogenesis, wh
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176 U.IGm..lln.apomictic pathway wi
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178 IJeIGr.........development with
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180 Ud Gr....lIoo,(Rhoades and Demp
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182 Ue5Gro........Meiosis is an alm
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184 Uel Gn...lIDo,To date, the phen
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186 Uei Gr....lIa..do not display p
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188 UtI GrOSllilaot.development of
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190 Ud e;,....1Ia..Arabidopsis, unp
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192 Ueli Gro".llae,system to identi
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194 UeI Gm..ikIonsystem developed b
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196 Ud Gro...ild...concentrate our
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198 lleIG
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200 UtlG09".ila,ndescribed that are
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202 UeIGfo...ll...Two additional po
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204 Uel G.....ilcmDiboll, A.G., and
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206 UeRG'....ild...--.1974. Reprodu
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208 Uel GtO,,"ikIa..MIodzik, M., Y.
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21 0 Ud Gromild.1S--.1982. Nature e
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Chapter 13Induction of Apomixis inS
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214 Uta Praebll aod Rod ScottCrosse
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216 Uta Praektlt.. Rod Scana minori
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21 8 Uta P...ke~ .d Rod S
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220 Ura P"",k.h .d Rod ScottStubby
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222 Uta Praekelt Old Rod S,ollelong
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224 Uta P...kek .d Rad Scaliresulti
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226 Uta P,..kelt ..dRod S
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228 Uta P..utt aod Rod 5
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230 1\omas Dresselhaus, Joh. G. (IJ
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progression or inhibition of develo
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234 T1lo.... Dr......... Jo~. G. (.
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236 TIoo.... D........., J.~. G. (a
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238 T1tonoas Dr......... Joino G. '
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240 no- P,ossdlaos, Jo. G.'-.... Y.
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242 1110""" 0,........, M. G. c,.._
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Chapter 5 Genetic Analysis of Apomixis - cimmyt

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