Hayashi, Jiro

Takahashi, Ryuhei

Okayama University Digital Information Repository

LINKAGE STUDY OF TWO COMPLEMENTARY GENES FOR BRITTLE RACHIS IN BARLEY

Okayama University Scientific Achievement Repository

LINKAGE STUDY OF TWO COMPLEMENTARY GENES FOR BRITTLE RACmS IN BARLEY R yuhei T AKAHASHI and Jiro HA Y ASHI In the previous experiment (1959b) the writers have indicated that the complementary genes， Btand Bt2， for brittle rachis in barley are both located on chromosome 3: one of them， Bt， islinked with an， ac and Xc with 1.24 %，13.62% and 15.31% recombination， respectively， and the other one， Bt2' and u;:; are in linkage with 17.90% recombination. However， itwas obscure whether Bt and Bt2 were very closely associated or considerably distant from each other. This study was planned to disclose the linkage intensity between Bt and Bt2 and their relation with two marker genes， Xcand al in the same linkage group. The writers wish to express their sincere appreciation to Dr. Philip G. Miles， Associate Professor， State University of New York at Buffalo， for his kindness in reading the manuscript. Thanks are due to Mr. Isamu Moriya for his kind assistance in the preparation of experimental materials. MA TERIAL AND METHOD A single cross between two cultivars with tough rachis， Colsess IV and Russian 82， was used as the material. The genic constitution of Colsess IV has Xc Al bt Bt2 ・ Xcal Bt already been known to be -;;一一ー 一一一~ and that of Russian 82一一一一一一Xc Al bt Bt2 ~..~ ...~. ~. ~_..~~..... ~- Xc al Bt bt. 予言，whereal is a gene for albino lemma and Xc品rxan伽 seedling(lethal). Since Colsess IV was heterozygous for x" the cross gave two kinds of F 1 h ybrids with Xc Al bt Bt2 ~_ Xc Al bt Bt2 genotype of either ~一一一一一一一 or--0一一一一一一一.For brevity， the former Xc al Bt bt2 - Xc al Bt bt2 genotype will be called xc-heterozygote and the latter Xc-homozygote in the following. From ~-homozygous Fl plants， a total of 215 F2 plants were raised and 144 out ofthem were subjected to detailed analysis. For the xc-heterozygote， 87 F2 plants and F3 strains were similarly studied. In order to know the genic constitution for brittleness of rachis of each of the F 2 plants， a total of 231 F 2 plants were crossed each with two kinds of genotype analysers which were already known to be of type W (btbtBt2Bt2) or of type E (BtBtbt2bt2)' As the result of the test-cross， it is expected that nine possible F2 genotypes wiU give the segregation of brittle and tough rachis plants in the ratios as shown in Table 1. 100 Berichte d. Ohara Instituts. [Bd. 12， Ht. 2， TABLE 1 Expected segregation ratios of brittle vs. tough rachis plants in the F3 and the following generation of test.cross with nine possible F 2 genotypes When crossed with F s phenotype F s genotype， Gametes btBts (W) Btbts (E) Brit.: tough Brit.: tough (1) Bt Bt Bts Bts BtBts al : none al : none (2)BtBtBtJtaifBBt bBtJ . al : none 1 : 1 Britle rachis (3)BtbtBtzBtafiBbtt Btz g 1 : 1 al : none (併伸4勾) E 1rLuBeω42s bBb“fらeg sら2 E 1 : 1 1: 1 (5) Bt Bt bts bts Bt bts al : none none : al(6) Bt bt bts bts bt bts 1: 1 none: al Tough rachis (7) bt bt Bts Bts bt Bt2 none : al al : none (8) bt bt Bts bt， {b;Btg bts none : al 1 : 1 (9) bt bt bts bts bt bts none : al none : al事 Theratio depends on linkage intensity between Bt and Bts・EXPERIMENT AL RESUL TS 1. Xc-Homozygote F 8 segregation Brit.: tough al: none 3 : 13 : 19 (1) : 7 (1)事al tough tough tough tough tough Table 2 shows segregation of green vs. albino lemma and brittle vs. tough-ear condition in the F 2 generation of the Xc-homozygote or the hybrid free from the lethal gene Xc for xantha seedling. Segregation of green vs. albino lemma character pair fitted well to an expected 3: 1 ratio. However， the observed phenotypes for brittle vs. tough rachis showed a slightly p∞r fit to a 9: 7 ratio， but a good fit to a 1: 1 ratio. Further， the fit of the observed frequencies of the four classes to the calculated on the basis of independent assortment of the two gene pairs， Alal and BtbtBt2bt2' namely 27: 21: 9: 7 or 3: 3: 1: 1 segregation ratios was found to be very poor， indicating the association of both pairs. In Table 3 is shown the observed number of different F 2 genotypes as determined by F 3 test and also test-crosses with two kinds of genotype analysers of type W (btbtBt2Bt2) and of type E (BtBtbt2bt2)' The'most important and remarkable fact in this result is that， with regard to the brittleness and toughness of rachis， only three genotypes， namely， two parental and their Fl hybrid types， were found and no other recombination types could be found. This obviously 1964) Takahashi et al.: Linkage of two genes for brittle rachis in barley 101 TABLE 2 F2 data for the Xc-homozygote : segregation of green vs. albino lemma and brittle vs. tough rachis and their interaction Item Green Green Albino Albino Total χ‘ britle tough britle tough Observed count 85 67 20 43 215 Calc. on 27: 21 :9: 7 90.8 70.5 30.2 23.5 215 20.17 Calc.on 3: 3:1:1 80.625 80.625 26.875 26.875 215 13.97 Item X‘ D. F. Probability Segregation for Alal (152 : 63) 2.1225 0.2 -0.1 Segregation for britle vs. tough (105: 110)， compared with 9 : 7 ratio 4.8391 く0.05Swegirteh gation for brittle vs.tough，compared 1: 1 ratio 0.1163 0.8 -O. 7 TABLE 3 F 2 genotypes from Xc -homozygous F 1 plant， as determined by F 3 test and the test-cross with genotype analyzers of type E (Bt bt2) and of type W (bt Bt2) Brittle bt Bt. Bt bt. AI AI AI al al al 7 44 18 Tough bt Bt. (type W) 石Bt. others AI AI AI al al al 20 12 。TABLE 4 Re-arranged data shown in Table 3 A. Alal-Btbt (repulsion) Doubly dominant group AIAI BtBt 0 Alal BtBt AIAI Btbt Alal Btbt 7 5 44 Singly dominant : group 1 AIAI btbt 20 Alal btbt 12 Singly dominant : group 2 alal BtBt 37 alal Btbt 18 indicate complete linkage of Btbt with Bt2bt2. B. Alal-Bt.bt. (coupling) Doubly dominant group AIAI Bt.Btz 20 Alal Bt.Bt. AIAI Bt.bt. Alal Btabt. 7 12 44 Singly dominant : group 1 AIAI btabta 0 Alal bt.bt. 5 Singly dominant : group 2 alal BtaBt. 1 alal Bt.bt. 18 Total 144 The data shown in Table 3 were then re-arranged and shown in Table 4. From five out of six sets of data recombination values of Alal and Btbt in repulsion 102 Berichte d. Ohara Instituts. [Bd. 12， Ht. 2，phase and those of Alal and Bt2ht2 in coupling phase were first calculated separately. Then al of the recombination values obtained were put together and average， weighted recombination values were estimated as Bt and Bt2 could be regarded to be on the same locus (Table 5). As seen in Table 5 itwas 15.37 :!:2.0261 (%). TABLE 5 Calculation of weighted p value for A1al and Bめt(=B0.bω Source of data P n I=ni pI Doubly dominant Alal-Btbt 0.1144 56 16.636 931. 616 l(賂.5768704Singly dominant-l 11 11 0.2308 32 7.438 238.016 54.934凹28Singly dominant-2 11 11 0.1957 55 8.894 489.170 95. 73056卯Doubly dominant Alal-Bti bti 0.1882 83 6.748 おO.随4 105.4078088 Singly dominant-2 11 11 0.1000 19 6.156 116.964 11.6964α)() SI = 2435. 850 SpJ = 374. 3457410 p=SpI/SI=0.1537 : ip=V市 1=0.凹ω612. Xc・昂terozygoteAs stated before， this hybrid included four pairs of genes， Xcxc， Alal， Btht and Bt2ht2' in heterozygous condition. And， because of the lethal effect of Xc for xantha seedling with which three other pairs were in linkage， F2 segregation of green vs. albino lemma and brittle vs. tough ear character pairs considerably deviated from the expected 3: 1 and 1: 1 ratios， respectively. This made it di伍cultto investigate linkage relations wih F 2 data. TABLE 6 F2 genotypes derived from the xc-heterozygous Fl plant， asdetermined by test-cross with two types of genotype analyzers， type W and E Brittle携?Wh揺tyh議?ωers Total AIAI Alal alal AIAI Alal alal AIAI Alal alal xc/ X.乞Xc/Xc o 3 8 o 41 2 0 3 2 0 3 3 。 18 ????Total o 44 10 07 0 o 8 18 In Table 6 are shown frequencies of various genotypes among the F 2 plants derived from the xc-heterozygous Fl plants. These were determined by F3 progeny test and also test-cross with two kinds of genotype analyzers for brittleness of rachis. It is noted in this table that with regards genic constitution for brittleness of rachis only parental and F 1 hybrid types have. been found and no recombinants existed among the F2 plants analysed. Linkage intensities of Xcxc and Alal and also of X九 andBtht (Bt2ht2) were 1!渇4J Takahashi et a1.: Linkage of two genes for brittle rachis in barley 103 estimated from the data shown in Table 7 that were obtained by re-arranging the data in Table 6. The results are shown in Tables 8 and 9. The same kinds of results were then combined and the weighted average recombination values were calculated. The estimates obtained are 5.48士1.7884(%) for Xcxc and Alal and 18.23:!: 2.6953 (96) for Xcxc and Btbt or Bt2bt2・A. xc:rc -Alal (Repulsion) 1. Doubly dominant XcXc AIAI 0 Xc:rc AIAI 3 XcXc Alal 5 Xc:rc Alal 50 2. Singly dominant XcXc alal 27 Xc:rc alal 2 TABLE 7 Re-arranged data in Table 6 B. Xcxc-Btbt (Coupling) 1. Doubly dominant XcXc BtBt 19 Xc:rc BtBt 7 XcXc Btbt 1 X以cBtbt 43 TABLE 8 C. Xc:rc-Bt.bt. (Repulsion) 1. Doubly dominant XcXc Bt，Bt， 2 Xc:rc Bt，Bt. 5 XcXc Bt.bt， 11 Xc:rc Bt，bt， 43 2. Singly dominant XcXc bt.bt. 19 Xcxc bt，bt. 7 Calculation of average weighted recombination value between X山cand Alal Source of data n I=ni pI Doubly dominant Singly dominant P 0.0750 0.0357 58 29 26.244 1522.152 114. 1614似淘57.2665842 55.314 1604.1伺p=SpI/SI=0.0548 : ip=Vη百=0.017884TABLE 9 SI=3126.258 Spl=171.4279842 Calculation of average weighted recombination value between Xcxc and Btbt or Bt.ttz Source of data P n I=ni pl Doubly dominant Xc:rc-Btbt 0.1952 80 6.356 筑)8.480 99.255296。Doubly dominant Xc:rc -Btzbt. 0.1848 61 9.366 571. 326 105.5810448 Singly dominant 11 11 0.1556 26 11. 412 296.712 46.1683872 SI= 1376. 518 Spl=25l.∞47280 p=SpljSI=0.1823 : ip=vη豆1=0.026953DISCUSSION Genetic analysis was made of 231 F2 hybrid plants of a cross between two cultivated varieties， Colsess IV and Russian 82， differing with each other for the gene pairs， Xcx" Alal， Btbt and Btzbt2・ Theresult was that Bt and Btz were linked so completely that any kind of recombinant types was not found， though 104 Berichte d. Ohara Instituts. (Bd. 12， Ht. 2， the number of plants analysed was t∞small to draw such a conclusion. In spite of this， however， the Fl hybrid of this and similar crosses have been found to be of brittle rachis， indicating that Btbt and Bt2bt2 are non-allelic. So， it may be safe to consider that these two gene pairs are pseudo-allelic. There are many examples of pseudo-allelic genes in animals and plants. Komai (1950) has suggested that these probably have differ官 ltchromosomal bases as their origin. So， it is a problem of interest to know how the pseudo-allelic loci under consideration have originated. In any case， itmay be possible to suppose that the origin of these two recessive genes， btand bt2， could be attribu・table to different mutations that have occurred independently. Next， let us consider the distance between and order of arrangement of Btbt and several other genes on chromosome 3. From the results obtained in this experiment the distance and relati ve position of three genes， xc， aland bt (=bt2) may be represented as shown in the upper part of Fig. 1. Robertson (1937)， Takahashi and Yamamoto (1951)， Takahashi and Hayashi (1959 a， b)have estimated the recombination values between 町，a.， x.， al， a"and bt (= bt2) and ha ve suggested their locations on chromosome 3 by genetical studies with different crosses. The known distances between these genes are shown together in the lower part of Fig. 1. There are two questions in this chromosome map. One is the relative position of Xc and a.， of which we have previously made a brief comment (Takahashi and Hayashi 1959 a). Robertson (1937) is of opinion that Xc is located at the right side of ac・ However，it seems more plausible to uz ト日8--r二ふ11r→-3η トー&ト←三ゴ9.34・10.17(14.41)一~14.23----"'4 15.75(18.95 17.90 Fig. 1. Severa1 genes on chromosome 3 : their arrangement and distance， constructed with the data by Robertson (1937， with asterisk) and Takahashi (1951)， Takahashi & Hayashi (1959a， b and this report). consider that Xc is at the left of ac for two reasons: the distance xc-al (5.48%) is 1!お4J Takahashi et al.: Linkage of two genes for britt1e rachis in barley 105 1.75% longer than that for ac-al (3.73%) and the disiance xc-ht (15.31%) is 1.69 % longer than that for ac -ht (13.62 %). It is noted in this connection that some di伍cultiesare encountered in ascertaining this inasmuch as Xc and ac appear to be rather closely associated and moreover， they are the genes for lethal which r吋ectto three point test. Location of ht may be another problem that needs further scrutiny， although we have tentatively placed it at the right of a，.， only because of the longer distance between al and ht than that between al and a船SUMMARY A study was made of the linkage intensity between two complementary genes， Btht and Bt2ht2， for brittle vs. tough rachises of barley and also of their relations to X九 forgreen vs. xantha seedling and Alal for green vs. albino lemma character pairs. The results obtained may be summed as follows: 1. Two genes， Btht and Bt2ht2， were found to be pseudo-allelic: complementary action of Bt and Bt2 in the heterozygote suggested that these two were on different loci， but no recombinants were recovered in F 2 of a cross between two di町erentgenotypes， BtBtht2ht2 and hthtBt2Bt2' 2. Linkages of Bt and Bt2 with Xc and al were confirmed. The recombination values obtained are: Bt (=Bt2)-al...…15.37士2.0261(%)Bt (=Bt2)-Xc"….18.23士2.6953(%)Xc - al..…5.48:!: 1.7884(%) 3. From this and some other previous results the order of arrangement of several genes on chromosome 3 was determined and shown in Fig. 1. LITERA TURE CITED Komai， T.1950. Semi-allelic genes. Amer. Naturalist 84 : 381-392. Robertson， D. W. 1937. Inheritance in barley IJ. Genetics 22 : 443-451. Takahashi， R.and Yamamoto，J. 1951. Studies on the cla個ificationand geographical distribution 。fthe J apanese barley varieties， 11.On the linkage relation and the origin of the ‘uzu' or semi-brachytic character in barley. Ber. Ohara Inst. landw. Forsch. 9 (4) 399-410. Takahashi， R.and Hayashi， J.1959a. Linkage study of albino lemma character in barley. Ber. Ohara Inst. landw. Biol. Okayama Univ. 1 (2) 132-140. Takahashi， R.and Hayashi，J. 1959b. Linkage study of the complementrary genes for britle rachises in barley (Preliminary). Nogaku Kenkyu 46 (3) 113-119 (in J apanese). 

LINKAGE STUDY OF TWO COMPLEMENTARY GENES FOR BRITTLE RACHIS IN BARLEY

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