CYTOGENETICS AGR 6353
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This 16 page Class Notes was uploaded by Elaina Gorczany on Friday September 18, 2015. The Class Notes belongs to AGR 6353 at University of Florida taught by Kenneth Quesenberry in Fall. Since its upload, it has received 19 views. For similar materials see /class/206615/agr-6353-university-of-florida in Agricultural & Resource Econ at University of Florida.
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Date Created: 09/18/15
XIII Autopolyploids AGR 6353 Cytogenetics Fall 2007 K H Quesenberry N A Types of Autopolyploids Euploids Changes in whole sets of chromosomes Polyploids General comments a Evolutionarily important b Counteracting to chromosome reducing mechanisms c about 13 of all angiosperms are polyploid d Almost 70 of grasses allopolyploids B General Chracteristics Higher chromosome number results in increased nuclear and cell volume N General larger vegetative parts a More frequent in perennials P Higher frequency of selfers in autopolyploids as Infrequent in animals 6 Often have become diplol N C Sources of Autoployploids Natural Low frequency in nature a Cell regeneration cut ends callus 39Ol39l ture d treatrnent natura a Corn b Colchlclne 1 Blakeslee 1937 rst use All major agronornic crops have been oubled with little value Ex Red clover and rye grass 2 important forsynthetic arnpnidiploi s 3 Techniques forusing colc icine a seed b seedlings c buds d crowns c N20 laughing gas Must have fertilized zygote d Others Dryzalin trirluralin D Chromosome Pairing 1 1 Autotetraploid a Quadravalent b Trivalent and univalent c Two bivalents 2 Rheduced fertility may be due to lack of II pairing owever many first generation colchicine doubled species have high frequency of II than one would expect D Chromosome Pairing 2 Ex Table 79 and 30 Bumham p 177 173 snowing various chrom osome associations in autotetraploid Brassica campestris Generation IV ll stained Pollen seed no 2 7 395 616 1163 926 15 119 05 163 920 1493 902 163 2n 133 0 range See Taylor et al 1976for red cloverCrop Sci 16 516513 Generation I II III IV i1 0 10122 6141o43 01013 os133 E Segregation of Autopolyploids 1 1 Chromosome segregationThe chromatids in a particular gamete derived from a multivalent belong to separate A A AAAa E Segregation of Autopolyploids 2 2 Random chromatid segregation Any one chromatid may mumat c llum e infinite number of CD S occur between the gene and centromere AAAAAAaa e AAAAaaaa 1AA 12Aa 15aa Aaaaaaa E Segregation of Autopolyploids 3 3 Maximum equational segregation Occurs i a Quadrivalents are always formed b There is at least one no between gene and centromere c There is random segregation of chromatids at A ll This is one of three possible possible arrangement arrangements aa cc bb dd Third possible arrangement aa dd Ecdd bbcc d Possible segregation types from quadrlvalent Mend of Segregation Types DIV Alt Ad Ad gem 1 15 2 Total1oab1oac1o Iswn Ion 26 24 M ad1obc1obd1ocd 3aa3 bb3cc3dd chromatid pairs ab cd ab ab ab cd quot9 P 39 5 3 v 3quot C bv substitute AAAa for abcd end 1st DIV 35AA30 Aa3 aa 131o1 at end om 2acbd 2ab 2acbd gametesorspores warm F Double Reduction Ratios for Tetrasomlcs and Tetrap0lds 1 Two modes of n1gamete formation are possible a The two genes in the n1 gamete came from different chromosomes b The two genes in the n1 gamete came from the same chromosomes ie double reduction Calculation ofgamete frequencies intenns on a There are 4 types of double reduction gametes aa bb cc ddo b The nondouble reduction gametes are ab ac ad bc bdcd 1a c List ofthe frequency ofdouble reduction and nondouble reduction gametes in terms of infer a triplex tetrasome F Double Reduction Ratios for Tetrasomlcs and Tetraploids 2 c List of the frequency ofdouble reduction and nondouble 39 39 ulul 39 Double Reduction Types Nondouble Reduction Types Types Alleles Freq Types Alleles Freq aa AA 14 ab AA 1 16 bb AA e114 ac AA 1a16 cc AA on ad Aa 1 16 dd aa 14 bc AA 1a16 bd Aa 1 16 cd Aa o F Double Reduction Ratios for Tetrasomics and Tetraploids 3 d Then from an AAAa individual triplex gam etic frequency are as follows Gam etes AA Aa aa Substitute G 1 Segregation of Trisomics amp Triploids 31 all H Com parison of 3am etic Frequencies Expected From Chrom osome and Maximal Equational Segregation Table as Eurnnarn p 188 1 TetrasomicITetraploids Genotype chromosome Maximum Equational segregation segregation cameoes quot1 aa cameoes quot1 aa AAAa AA Aa 0 15AA 1oAa aa 42 AAaa AAMAaraa 1s7 2AA 5Aa 2aa 222 Aaaa A 50 AA 1oAa 15aa 542 2 TrisomicslTriploids with 50 or 25 n1 transmission TableBA aurnnam p 13 9 m n quot1 aara n1 n quot1 aara 50 n1 AAa AA2Aa 2Aa 167 5AA6Aaraa BAN 205 Aaa 2Aaan A2a 500 AA Aa5aa 4A a 542 25 n1 AAa AA2Aa SAKS 50 5AA6Aaraa 24A12a 270 Aaa 2Aaaa 3A4 a 5a AAeAa5aa 12A24a 604 F Double Reduction Ratios for Tetrasomics and Tetraploids 4 e Gametic segregation ratio in terms offrom atetrasome from triplex duplex and simplex cond on Gametes 2n2 Genotypes AA Aa aa AAAa AAaa Aaaa 2 Sam etic frequency in terms ora Triploidl Trisomic a List of frequencies ofdouble reduction and nondouble reduction etes in terms of for duplex trisome AAa Double Reduction Types Nondouble Reduction Types Types Alleles Freq Types Alleles Freq aa AA an ab AA 1113 bb AA an ac Aa my cc aa on be Aa 11 a 111 h 39 condition 2n 1 3am etes Genotypes AA Aa aa AAa Aaa I Expected Tetrasomic FZ Ratios for Chromosome and Maximum Equational Segregation Table 86 Burnham p 190 Typeof Ratio quot1 AA A3 AZaZ Aa3 aA Aa a AAAaA3a cnrom 1 2 1 allA oo maxe 155 250 12s 20 1 5751 0174 AAaaA2a2 cnrom 1 a 15 a 1 551 25 max eq 4 20 51 20 4 774 515 AaaaAa3 chrom 1 2 1 31 250 maxeq 1 20 126 260 165 407165 2503 J Rate oprproach to Homozygosis from Selfing Diploids and Tetraploids Table 94 Burnham p 196 Generauon pr owd TetragowdAaaa Tetragowd AAaa Aa c x Eq ax Chrom 1 05 025 0295 005 0098 2 o 75 o 38 o 46 0 1g 0 28 3 o 875 o 49 o 58 0 33 o 44 4 o 9375 o 58 o 87 0 44 o 57 5 0 98875 0 85 o 75 o 53 o 88 Approach 75 faster Wm maxwmum equatwona segregatwon than Wm chrom osome segreganon X Haploids AGR 6353 Cytogenetics Fall 2007 K H Quesenberry A Types of Haploids 1 Monohaploids 2 Polyhaploids 3 Nullihaploids B Origin of Haploids 1 1 quotSpontaneou quot plants and animals 55 p 244 a Abnormal development b Twin seedlings hlh dd or dh c Parthenogenesis seedling markers 2 Induced a lnterspecific wide hybrid example In nigrum X S Iuteum 7 of 35 plants were S nigrum haploids Solanu Example ofmatroclinal pseudogamy ie 9 required for stimulation of embryo development but embryo develops without fertilization 2 Induce a lnterspecific wide hybrid example 2 B Origin of Haploids 2 d S tuberosum X S phureja Identify S tuberosum haploid by lack of pigment Rowe 1974 listed 39 species which produced haploids afterwide hybridization B Origin of Haploids 3 2 Induced b ln39adi on and chemicals 1 Examples in tobacco wheat Crepis oenothera pop ar 2 Apparently irrad39 tion of pollen at proper dosage may destroy ability to fertilize but it stimulates embryo developmen eat pollen with TB reported 3 Toluidine blue Tr tomato maize nd poplar Also treat pistil during in time of pollen tube development 282 haploids in 1192 B Origin of Haploids 4 2 lnduced c Alien c oplas Aeqilops caudata x Triticum aestivum x T aestivum 53 haploids but no haploids without alien cytoplasm B Origin of Haploids 5 d Anther culture 1 Came into vogue in late 196039s early 197039s with first work on Datura soon after on tobacco 2 May get nearly 100 haploids in some spec39 by direct formation of plants from immature pollen more than 1000 plants per anther 3 Many species yield no haploids from anther culture Cer als have been especially difficult However one report says successful anther culture for haploids in 171 species of 60 genera in 26 families 4 In addition to plant species other a Developmental stage of micr factors such as re b Composition of culture med ospo B Origin of HapIOIds 6 2 lnduced d Anther culture examples of genetic and environmental effects on succes 1 Best success at uninucleate stage 2 Anther from main spike is better than from tiller 3 Cold pretreatment before planting anther may help 4 Elevated sucrose lower ratio of NHAINOS Some suggest natural extracts potato 5 Initial culture for 8 days at 33 C then transfer to 24 C improved frequency of differentiating plant B Origin of Haploids 7 2 lnduced e Chromosome eli ination Best example is Hordeum vulgare 2n14 x H bulbosum Reports of as high as 215314 embryos were haploid 2 The H bulbosum chromosomes are selectively eliminate at 35 days post pollination 40 of embryos were haploid but at 11 days 94 were haploid Embryo rescue must be used to obtain haploid plant B Origin of Haploids 8 2 Induced f intergeneric wide hybrids 1 Laurie and Benett 1988 TAG 73403409 31 wheat haploids from 706 maize pollinated florets 2 c Suenaga and Nakajima 1989 PI Cell Rep 8263266 Improved frequency of haploid ofwheat by inje n 24 D into uppermost node of wheat stem after maize pollination Rines and Dahleen 1990 CropSci 3010731078 14 haploid oat plants from 3300 maize pollinated oat florets B Origin of Haploids 9 2 Induced f intergeneric wide hybrids O donoughue and Bennett 1994 TAG559566 Durum wheat haploid production using maize wide crossing 4 Almouslem etal1998 Crop Sci 3810801087 Haploid durum wheat production via hybridization with maize Pollinated seven durum wheat Triticum turgidum L 2 394x28 AABB cultivars with pollen from three maize cultivars In vitro culture produced haploid seedlings Post pollination treatment with 3mb L391 2 D and 120180 mg L391 gave best yield of embryos Were Istinct cultivar difference in numbers of haploids produced C Meiotic Behavior of Haploids 1 1 Monohaploids a Are very irregular at Ml b May see same pairing due to chromosome duplication c Synaptonemal complex seen at pachytene in tomato maize etc d Spindle at MI disorganized e Distribution of chromosome at Al is random C Meiotic Behavior of Haploids 2 2 Polyhaploids a Can be either autopolyhaploid or allopolyhaploid 1 If allopolyhaploid usually have little pairing but may have some homoeologous pa ng If true autopolyhaploid then expect higher frequency of pairing 3 Pairing influenced by genes also b May produce segregants in doubled progeny D Uses of Haploids 1 1 Gene expression studies No dominantrecessive condition to interfere 2 Double for immediate homozygosity a Very useful in selfpollinated crops and for inbreds for hybrids in crossed species 939 May shorten time from cross to variety release to 5 6 years rice barley wheat tobacco 5 May not always result in 100 homozygosity D Uses of Haploids 2 3 Breeding at the diploid level potato alfalfa 4 How to double haploids a Tissue culture tobacco b Colchicine c Cut or wound d Spontaneous V Cytological Analyses and Genetic Control of Meiosis Singh Ch 4 AGR 6353 Cytogenetics Fall 2007 K H Quesenberry A Meiotic Analysis 1 1 Study chromosome pairin c g at ne F r evidence of duplications andor de ciencies inversions translocations bD i loteneDiakinesis For evidence of chiasmata frequency c At b or Ml for pairing relationships 1 ln diploids failure to pair indicates some lack of 2 ln polyploid X diploid cross may identify homologous genom A Meiotic Analysis 2 1 Study chromosome pairing at For presence of bridgeslaggards frequently from inversions or poor pairing and for unequal segregation e M llA II For unequal segregation and presence of micronuclei f Pollen formation For presence of shriveled unstained pollen and micronuc ei A Meiotic Analysis 3 2 How to record calculate and report meiotic pairing data a Determine exact chromosome number b Observe and record exact pairing relationships in minimum of 20 cells from plants c Calculate mean pairing frequency by calculating the mean of all configurations A Meiotic Analysis 4 Chromosome configerations Cell II III IV 1 2 7 2 2 5 1 3 1 6 1 4 6 1 5 8 Total 5 32 1 2 Mean 1 6 4 02 04 Check 1 128 06 16 B Genetic Control of Meiosis 1 Prem eiotic mutants 2 Synaptic mutants First by Beadle amp McClintock 1928 a Highest number in grasses 2nd highest in legumes b Most in 2n 2x species c Spontaneous and induced pollen or ovule abortion d Single genes Singh Tables 44 45 e Pairing related to temperature humidity chemicals 3 Chromosome disjunction mutants a Divergent spindle b Precocious spindle c 2n gametes parallel spindles B Genetic Control of MeIOSIs 2 4 Cytology of mutants a Asyn ps39s absence of II bivalents 1 At pach ene 2 Disjunction is irregular 3 Synaptonemal Complex SC does not occur 1 Failure of chiasmata maIn enance 2 Wider central region of SC 3 S ro en own more rapidly 4 Higher frequency of univalents at Ml b Desynapsis Failure to maintain associations c Univalent behavior 1 Random to poles without division 2 Equational division at MI 3 Fail to move to either pole 4 More discussion in haploidy topic later 5 Diploid Like Meiosis in Allopolyploids Genes Controlling Homologous Pairing a 5B Ph gene in wheat 1 Concept of homoeology 2 Effects of 5B Homoeologous rou r chromosomes b Similar genes found in other species 6 Male sterility a Nuclear genetic male sterility Mostly single gene 1Structural 2Functional 3 Sporogenous a Abortion of microspores b Deformed tapetum b Cytoplasmic ms Inherited maternally c Cytoplasmicgenetic ms Interaction of nuclear a d cytoplasmic genes XI Allopolyploids AGR 6353 Cytogenetics Fall 2007 K H Quesenberry A Terminology 1 Diploids AA A39A39 BB 2 Autopolyploid AAAA 3 Segmental Allopolyploid AAA39A39 4 quotTruequot Allopolyploid AABB 5 Autoallopolyploid AAAABB 6 Homoeologous chromosomes Those that are only quotpartiallyquot homologous 7 The amount of homology varies from total autopolyploid to almost none allopolyploid 8 Genome The basic set of an organism B Chromosome Pairing 1 1A1A1 AZAZ B131 BZBZAII llbivalents A 2 A131 A131 AZAZ 3232quot amplVquadravalents J J 3 AA AA 313 etc II amp IV and others 1 Autosmdetic pairing or autosmdesis also homogenetic Pairing of chromosomes from same genome 2 Allogyndetic pairing or allogyndesis also heterogenetic Involves pairing of chromosomes from different genomes 3 No special name Pairing within the genome resulting from duplications or translocations within the genome C Chromosome Pairing 2 1 quotTruequot allogolygloids all l39s if little or no homology Highly sterile 2 Segmental allogolygloids vary from l39s ll39s Partially sterile 3 Autopolyploids May have fewer than expecte d multivale nts 3 a C Chromosome Pairing 3 Examples from the genus Trifolium T pratense X T diffusum 1 2n2x14 2 2n 3 2n4x28 4 2quot Chromosome Pairing Configuration Cross II III IV V VI gtV 1 X 2 159 130 051 038 018 014 023 3 X 4 089 901 070 105 025 018 Trace 3 050 4 69 0 23 436 8 4 054 518 025 509 C Chromosome Pairing 4 X T heldreichianum 2n2x16 b T alpestre 2n2x16 Chromosome Pairing Configuration II III IV V W 010 795 c T alpestre X 2n T rubens 2x16 2n2x16 Chromosome Pairing Configuration II III IV V W 046 777 D Chromosome Pairing in Polyhaploids to Reveal Genome Homology Species Parent Number in Pairin somatic haploid in haploids umber T compactum 42 6x 21 03 II T e 42 6x 21 16 II avg Aegilotriticum 56 8x 28 03 II N tabacu 48 4x 24 03 H N tabacum 48 4x 24 1 II D menonensis 112 16x 56 512 II S nigrum 2 6x 36 512 II P argentarum 72 4x 36 18 II M tiva 32 4x 16 II S tuberosum 48 4x 24 12 ll A desertorum 28 4x 14 57 II E AmphIpIOIds Amp pl diploid interspec Ic 5quot oids Double the chromosome number of a 39 hybrid May also be produced by making an autoploid of each diploid parent and then crossing these autoploids If the two parental species are genetically distant then the amphidiploid will be a quottruequot alloploid with mostly ll39s If the two parental species are less genetically distant then we have a segmental alloploid with I II III nd IV We may have F2 breakdown in alloploids amphidiploid Caused by evolutionary differences between species F Allopolyploid Genome ID 1 1 General example Suspect Possible Allopolyploid X Diploid ProgenitorA 2n4x32 2n2x16 6 8 F1 8 II 8 Note Other Diploid X Allopolyploid 24 Suspect Possible Allopolyploid X Progenitor 2n4x32 B 16 ll 1 F18ll8l 2n2x16
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