イネの粒長に関するQTLの主効果および2QTL間相互作用に関する準同質遺伝子系統を用いた解析

NII-Electronic Library Service J.CropRes,

55

:

33-38

==

Research

Article

(2010)

Main

Effects

ef

Indiyidual

QTLs

and

Interactions

between

Tvve

QTLs

Controlling

Grain

Length

of

Rice

under

Near-Isogenic

Lines

Tsuneo

Kato

Faculty

ofBiology-Oriented

Scienceand 7lechnologMKInkiUnivensity

<Kinokawa,

Wakayama,

649

-

6493,

Japan)

Summary:

Tlie

objectiyes of

this

study were to evaluate

the

main effects and interactionsDf individual

quantitativetraitloci

(QTLs)

for

_grain

lengthand theircombinations

in

rice.Fiveprimarynear-isogenic lines

(NILs),

each of which hadan alleleforlong_grainonly atone of five

QTLs

controlling _grainlengthof a

large-graincultivar,

`BG

1',and an allele forshort _grainlengthat the other four

QTLs,

were constructed with a common _geneticbackgroundof a small-grain cultivar,

`Gimbozu'.

Illaddition, an NIL'involvinga major _gene

for

long

grainof `Fusayoshi',

L.of,

inthesame

background

as above was developed.From intercrossingof these

primaryNILs,phenetypic selection,and _progenytests,15advanced NILs,each of which haddifferentalleles for

long_grainonly atone of

the

10

combinations offive

QTLs,

and one of thefivecombinations of five

QTLs

and

LkXwere furtherconstmcted. Themain effects

(additive

effects) and interactions

(epistatic

interactions)of

QTLs

s t

and Lefon _grainlengthwere estimated fromthemean _grainlengthsof theseNILs and Gimbozu cultivatedover two _years.The main effect of LigCwasthelargest,foIIowedbythosethe

_QTLs

showing a ]argeand signMcant variation among them. T:hecorrelation coefTicient betweenthetwo _yearsforthemain effects was highand significant

(r=O.95"),

suggesting thatthe

QTLs'

main efEects were consistently expressed at

their

own magnitudes forthetwo different_years.The

interactions

between

two

QTLs

were abo'ut

half

the

strengthofthe main effects intheirmagnitudes and aisoshowed a large,significant variation among

QTLs.

The

_year-to-year corre!ation forthe interactionswas, however,not significant

(r=O.63),

Theseresults suggested that

QTL-by-Q[[IL

interactionscould contribute totheinstabilityof character expression and could _playan importantrole in

genetic

systems controlling

_quantitative

traits.

Key words: _grainlength,

interaction,

rnain effect, Oryzasativa L.,

QTL

lntroduction

Quantitative

traitsare _geneticallycontrolled by multiple

quantkatiyetraitloci

_(QTLs),

each of which

generally

shows a smaller effect comparecl with non-genetic factorsand acts ina cumulative manner with other

QTLs

cencerned with thesarne

trait.These characteristicsof quantitativetraitshaye made it

difficult

to estimate indiyidualgenotypes

from

observed

phenotypes,which show a clear contrast to qualitatiyetraits contrelled by major _genes.Tlierefore,several statistical

parameters,variance, covariance, mean, etc., hewebeenadopted as indispensable_procedures to analyze and deal with

quantitativetraitsinbreeding

_(Kearsey

and Pooni

1996),

The discoveryand developmentof various molecular markers, rnost of which are based on _{polymorphisms} innucleetide sequences, _gavearevolutionary impacton theabove situation: theindividualgenotypes concerned with aquantitativetraithave beenidentifiedclearIy, atleastforone ofthemultiple

QTLs

for

thistrait,basedon closely linkedmolecular markers thatbehave

Acccepted:March15,2010

Correspending author :TsuneoKato

(tkato@waka.kindai.acjp)

as typical_qualitativetraits.Ihisenables us to_position

QTLs

individuallyon an appropriate molecular linkagemap and to estimate their_gene actions and interactionsthroughseveral

algorithms

(Lander

and Botstein

1989,

Thriksley

1993,

Tbnksley and Fulton

2007).

On theother hand,thedetectionof

QTLs

strongly depends upon the levelof the threshold

_(LOD

threshold,etc.) which can be determinedrather arbitrarily by experimentei's,

This

is

aseriousproblem,particularly

for

QTLs

with small effectsand

QTLs

linkedcloselytoeach other

(Yano

and Sasaki

199b.

Thcrrefore,the existence of

QTLs

should be confirrned

throughother _proceduresand materjals, such as near-isogenic

lines

_(NILs)

_(Lin

etat,

2003),

chromosome segment substitution

lines

_(Kubo

et at.

2002),

etc, Sefar,alarge number of

QTLs

havebeendissectedindividuallyusing theseadvanced materials and identifiedas a definiteregion inthe _genome invarieus organisms

(e.g.,

Fan et al.

2006,

Song et al.

2007),

However, such dissectionof rnultiple

QTLs

intoasingle factorinevitably makes itimpessibletoeyaluate any

QTL-by-QTL

interactions, which are another importantcharacteristic of

Q[[Ls.

Therefore,

pyramidingof thesedissected

QTLs

forthesame traitintoan

CopyrighturasMlop･

veptWfftk(Tlte

Seciety of CropScience and Breeding inKinki,Japan)

The Society of Crop Science and Breeding in Kinki, Japan

TheSociety ofCrop Science and Breeding in Kinki, Japan

J,

Crop

Res,

_55(2010)

NIL

is

necessary toanalyze theinteractionsamong

QTLs,

Previousreports by the

present

author have

dealt

with the grainlengthof rice

(Oryza

sativa L.)as a typical _quantitative traitand havetriedto dissectfive

QTI.s

controlling _grainlength of a 1arge-graincultivar `BG

1'

(Kato

1998,

Kato

2005).

Consequentiy,a series ef fiveNILs with a cornnion _genetic

background of a cultivar 'Gimbozu' haye already been

developed:each of thefiveNILs has an aileleforlong_grain

derivedfrom `BG

1'

at only ene of the

five

QTLs

and

has

the counterpart alleles forshort _grainderivedfrom

`Gimbozu'

atall

fouTother

QTLs

(Kato

2005).

From intercrossjngof these

primaryNILs

for

rice _grainlength,the_presentstudy further constmcted aseriesof

10

advanced NILs, each ofwhich had two

alleles forlong_grainatonlyone combination oftwo

QTLs

and

had thecounterpart alleles fbrshort _grainat the threeother

Q[['Ls,

The objectives of the _presentstudy were to investigatethe main effects

(additive

efiiects)of individual

QTLs

for

_grain

lengthand theinteractionsbetweentwo

QTI.s

among thefive, using theabove _primaryand advanced NILs, inaddition, the main effect of amajor _genefor_grainlength,LdyConchromosome

3

_(Takeda

and Saito

1980)

and the interactionsbetween the

individual

QTLs

and Lkfwere alsoevaluated using NILs of

the

same kind.

Several

novel characteristics

for

the

QTLs'

main effects and

QTL-by-QTL

interactions

for

rice

_grain

length

are

discussed.

Materials

and

Methods

Five

primary

NILs

for

rice grain

length

were eonstructed through the_procedures

described

_previously

(Kato

1998,

Kato

2005).

Inthis_process,recombinant

inbred

lines

(RILs)

were

developedatfirstfromacross between`BG 1'and

'Koshihikarj',

a cultivar with short _grainlength,Each of fiyeRILs showing

t

t;tt

different_grarnlengthswas crossed with Gimbozu _, another

cultivar withshert _grain length.Segregantswith thelongest

graln length in each F2 _populationwere successively

backcrossedwith therecurrent _parent,`Gimbozu', as a_genetic

background.Consequently,four_populationsof BCsF2and one

BC4F2,each of which showed a typical segregation for_grain

lengthas a single Mendelianfactor,were obtained

(Kato

2005).

FiveNILs were established as true-breeding linesfrem the

respective ]ongest-grainsegregants inthe F2_populations,and

designated

as

NIL-a,

NIL-b,

NIL-c,

NIL-d,

and

NIL-e,

From

iso-allelismtestsforall_possiblecombinations

(data

not shown), alleles forlong_graininthesefiveNILs were confirmed toercist at

different

QTLs.

Tliesealleleswere recessive against the

alleles

for

shortgrain

in

al1

QTLs.

These

QTLs

were tentatively designated as _{qGin, gGth, qGhe, qGLd.} and qGLe forNIL-a,

NIL-b,NIL-c,NE.-d,and NIL-e,respcctively. Inthesame way,

a large-graincultivar `Fusayeshi', which hasa major

_gene

for

long

_ginin,

LkA hasbeensuccessivelybackcrossedinfivetimes

tl

t

t

tt

with Gimbozu, resulting m an NIL wnh Lifinthebaekground of 'Gimbozu'

(Kato

1997),

TT)isNILwas designatedasNIL-E

Tbcarry out _pyramidingof these

_Q

[Ls,thefive_primaryNILs

were intercrossedinal1

10

combinations without reciprocals. in each of theirF2_populations

_(about

150_plaants),the six

longest-grain segregants were selected and theirhomozygosity confirmed

for

the

long

_grain

length

inF3_progenies

(l2

plants per line).From these _progenies,true-breeding lineswere established as advanced NILs,illwhich alleles forlong_grain exist inevery combination of two

QTLs

out of five.These 10

NILs

for

10

_QTL

combinations were designatedasNIL-al)to

NIL-de. According tothesame

_procedure

asabove, NIL-Fwas cressed with each of thefive_primaryNILs.FiveNILs withUar and an allele forlong_grainat only one difTerent

QTL

were established, ThesefiveNILswere

designated

as

NIL-Fa

to NIL-Fe.

In

2007,

al1of these

2],

NILs and threecultivars, `Gimbozu', `BG

1'

and `Fusayoshi', were seeded innursery boxeson

16

May and transplantedina _paddyfieldef theFacultyof

Biology-OrientedScienceand Technology,KinkiUniversity,Japan,on

13

June,

In

2008,

15NILs

_(excluding

NIL-F

and

NIL-Fa

to

Nll.-Fe)

and

'Gimbozu'

were seeded on

14

May

and transplanted on

10

June

in

thesame

field.

In

both

_years,the_planting

density

was

30

cm inter-rowand

15

cm inter-hi11with asingle _plantper

hill.Eachlineconsisted of sixhills.Fertilizerswere applied as

basaldressingat the rate of 6 _g m'2 each

for

nitrogen,

phosphorous,and _potassium.Other

field

managements were

done

according tostandard cultivation _practicesforthisreglon.

Afterrnaturing. a_panicleon thelongestculm of every _plant was harvestedand air-dried, Five_grainson _{proximalparts}of

primaryrachis-branches along thetopof arachis were collected

fromindividual

_panicles,

Ihese

_grains

were measured fortheir

grain

length

_(between

thebottomand thetopof alemma except

for an awn) using a video-micrometersystem

(VM-50N,

Olympus Corp., Japan) equipped with a macro-zoom microscope

(SZHIO,

Olympus Corp,,_Japan).An average

length

forfive_grainswas regarded the_grainlengthof an individual

plant.

Based on themean

_grain

lengthof Gimbozu and thelengths of individualNIL

_plants,

themain effect

(additive

efTect) of the

ith

_QTL(or

of Lkf),Ai,was estimated as a fixed effect using the

fo11owingequation:

Xik=C+Ai+ Eik

(Eq,

1),

where Xikisthe_grainlengthof the kth_plantinaNIL with a

long-grainallele atthemb

QTL,

Cisacommon background

(the

mea" _grainlength of Gimbozu),and sikisa residual random

NII-Electronic Library Service

Main

EffectsofIndividual

QTLs

and Interactionsbetweentwo

QTLs

ControllingGrainLengthof Riceunder Near-IsogenicLines

variable drawnfromN

(O,

a,Z).

Afterestimating

A,

and4 of

the

two

QTLs

(or

a

Q[[L

and

zaD

fromEq.

1,

theinteraction

(epistatic

interaction)

between

the

ith

andJ'th

QTLs

(or

between

theith

QTL

and

op,

Iij,was

also

estimated as afixedeffect bythefollowingequation:

Xpt = C + Ai+ Aj+ Iij･+ sijk

(Eq.

2),

where Xijkisthe_grainlengthof thekth_plant

in

aNIL with

long-grainallelesat theithand

jth

QTLs

(er

the ith

_QTL

aiid Ljij). and Eijkisalsoaresidual random variable as Eik.

Results

and

Discussion

[[bble1 shows seyeral agronomic traitsof

the

present

materials

in

2007 and

2008,

Large,

significantvariationswere

foundinbothyearsamong NILsand alsobetweenNILsand the

t t

backgroundcultivar, Gimbozu, inngt en!y _grainlengthbut also most other traits.TheseTesults suggested the_presenceof some _pleiotropiceffects of _grain-]ength

QILs

on other traits,

Fig,

1

shows themain effbcts of _grain-length

QTLs

in

both

yearsand a major _gene,Lofin

2007,

estimated fromthedatain

Thb]e

1

using Eq.

I.

Significantvariations among

QILs

were

detectedinthemain effect jnboth_years

(P<O,Ol).

Thelargest

Table1Agronomic traitsottheNILsand thelrparentsused inthepresentstudy

Linei)

Daysto heediog

2co7 2oesPeniclesfhill2co1 2coSCulm

length 2oo7(on)

Grainlengthkem) Grainvldth im}

20(IS 2oo7 2oog 2oo7 2ooS

NIL-aNILthNlL-cN1L-dNIL-eNIL-FNiL-ebNIL-scNIL-adNiL7afiNlL-bcNIL-･bdNILmbeNtL-edNIL-eeNIL-deML-FaNIL-thNIL-FeNIL-FdNIL-･FeGimb.Bfl 1Ftisay. I03.797.598,597.2g9,4I03.51eo, 2le2.2102.3100, O 97.2100.0 97.5 98,8 98.7 96,SI02.5 99.0le3.2tOl,3le3. 7 gs,g 90.5 9L5 I04,O97.59S,295.7loo. 2

--99.SIOL5102.5102,7 96.G1oo, 5 g9.71oo2 98.e 94.2 98.

2

ge.s le.58.7 9.S 9,512.2ll.S 9.5 a.7 7.510, 2 8.8 9,3le. 5 7,811.5 S.2

9.2le.

210.5le.5 9.8 6.8 B.O12.0 9.3l3.0IO,Oll.O".3 le.3fe.o 9,3 9.715.311.310.5 9.816.ele.5 9.2 s.o 74.57e.873.568,375,884.77G.E70,274,3a4.o12.276.3SO.571.2IB.g71,385,287,786.279.886.767.014.2g6.8?2.561.064.'O71.370,3 6S.266.872.315.268.070.56g.366. S7S.312.2 67,758.2 6.36,1G.66.36.26.96.67.06.26.56.76.66,27.16.96.4Z57,2].7?.37.2S,69,57.66.15.96.56.25.8 6.56.96.06.16.46.45,96.Sg.66, 4

-5.59.3

3,73,33.4･3,63.23.53.S3.73,63.73,53.53.43.73.43.54.I3.63.53.93,4 3.34.1 3.6 3.63.23.33.63.2 3.53.S3.43.33.23.53.13.43.33.5

-3,43.9

LsD(o.el}2,O1.g4.e5.06.86.2e.2O.3O.2e,2

t)

_G}mb.

_and

_Fusay.

_indlcate

_Gimbezu

_and

_Fusayoshi,

_{respeetively.}

Flsher' s

F-pretected

Lso

at the

O.

Ol

probability Ievel.

`- '

meens that thematerlals were not available inthls year.

LSD

was ca1cu1ated using

The Society of Crop Science and Breeding in Kinki, Japan

TheSociety ofCrop Science and Breeding iri Kinki, Japan

J.CropRes.

55(2010)

ggEg

{

tsgs

Fig.I Ag

gggs

i:f,l

l･ aal

'

2cxn

'.

2eos

Maineftectsofindividual

QTLs

and a major _gene,

Lkf;on rice_graiRlengthovertwo_years.

Main effects with a common letterwere not significantly diherentat theO.Olprobabilityleve],

using Fisher'sF-prctectedLSD,

main effectwas obtained with themajor _geneLdy1Arnongthe

five

QILs,

eGLc showed thelargestmain effect compared tothe effect of Llj though therewas asignificantdifferencebetween

eGLc and LijZ The orders inthemagnitudes of themain effects among the

QTLs

were very similar forthetwo different

_years,

A highlysignificant correlation coerncient was obtained between thetwoyearsforthemain effects

(r=O.95,

P<O.05),although the

interactionbetween the yearsand

QTLs

by ANOYA was significant

(data

not shown). This findingsuggested thatthe

!t

t

QTLs

main effects were consistently expressed at theirown magnitudes forthedifferenttwo _years.

Song

et al.

(2007)

identified

one of

the

Q[ILs

controlling _grain size of a

1arge-grain

japonica

cultivar,`WY3', and

designated

it as GVV2,This

GIV2

encoded anopen readmg

frame

inyolying

the

domainof RING-typeE3ubiquitin ligase.Interestingly,thesame authors showed thatanother 1arge-graincultivar, `Oochikara', also

l

+

hasthesame Gwa. Oochikara was derivedfrom a

･cross

of

SachiminorVInabawaselfBG

1,

and BG

1

is

thesource of al1five

allelesforlong_grainat thefive_grain-length

QILs

as above.

Consequently,GW2 would correspond toone of thefive

QTLs

for

grainlengthexarnined inthisstudy,

Zhang et al,

(2009)

analyzed thevariation inthe number of spikelets inarice_panicle.identifiedfour

_QTLs

forthistrait,and

dissected

these

QTLs

intosingleMendeliall factors

for

each of fburNILs,

_just

1ikethe_presentstudy

for

rice_grainlength. They

also

demonstrated1argedifferencesinthe rnain effects among

thescfour

_QTLs:

_QTLs

with smaller effects could not be expressed suMciently dependingen the_growingenvironments,

Fig.

2

shows theinteractionsbetweentwo

_QTLs

for_grain

lengthinbothyears,estirnatedwith theEq.2.[Ihevalues of the

interactienswere mostly negative and showed a largesignificant variation among

QTL

combinations

(P<O.Ol).

In2007,the values of allinteractionswere significantly differentfromzero

CP<O.Ol),

whereas in2008thevalues of six outof

10

interactions

s

s

g

g

Fig.2

-ggsi･gg

･gg

g･

s

gFig.3

al "a4'gx2･a34L4as",fi.-(t7e,s-ag

l-..It'I'"

lts'Ll''l

2ecrr

eg.

k ts L.ve 2ooe

'y

ee

_tele

-I･ Oexb _;,ll ttangil,

:･･:

_i

'li:uelI-b,taI1l･ vaetu

l,1Io,op

/-l.f.rmdw...[1, ; de

･

t

ts

lnteractionsbetween two QTLs on rice _grain

lengthintwo years.

a xb, for _example, [ndicatesthe interaction betweenqGLa and _qGLb.

Interactionswith a common letterwere not significantiy dlfferentatthe O,OlprobabilityIevel, fromFisher'sFprotectedLSD, and those with ' and "

were significantly difterentfromzero at the

O.05and O.Olprobabilitylevels,respectiveiy,

qeL-#Lkf

,suT

I

rmim'

m.ts} l

ga

l-mm

.L lnteractions qGLa × LkL Nothelnteractions ditferentprobability

gGLbwhptxca'i"'nqtgcakca

_..A.

pt"Nttaf

'A.

.･

g

･t

e

･

between grain

maior _gene,Lkf,on rice_grain

forexamp[e,

'

between_qGLa and Lkf,

signMcant differences interactions at the O.05

with "and *t from zero at the

levels,respectively. t'

.t.--t lengthQTLs and a length.

indicates theinteraction

were detected among

probabilityIevel. were significantly O.05 and O.Ol

were not significantly different

_(PIO.05).

The order of magnitudes oftheinteractionsamong

QIIL

combinations changed

inthetwe different

_years,

altheugh highmagn'itude interactions

were consistentlyfoundin

both

_yearsinthesame combination

(e.g,,

qGLa x_qGLd),lrhecorrelation coefficient between_yearsfor theinteractienswas not significarit

(r=O.63,

P)

O,05)

and lower

thanthecoefficient forthesame kindformain effects. This result meant thatthe expression of thetwo-QTL interactionswas relatively unstable indifferent_years,which showed a clear centrast with thestable expression of

QTL

main effects, This

instahilityintheexpression inthe two-QTL interactionsmight

centribute to theinstabilityof the character expression of rice

grainlength,Theinteractionsbetweena

QTL

and Llj"areshown

NII-Electronic Library Service MainEffectsofIndividual

QTLs

and interactionsbetweenTkvo

QTLs

ControllingGrainLengthofRiceunder Near-IsogenicLines

smalI compared with two-QTL interactionsinFig.

2,

and net significantly

different

among them

(Pk

O,05).

Thevalues of two

interactionsoutof fivewere fiotsignificantly differentfromzero

(P)

O.05).

Linet at,

(2000)

demonstratedepistaticinteractionsamong

threemajor

QTLs

controllingheadingdateofrice,Hdl,Ild2,and

Hd3,usingaseriesofnear-isogenic Iines,inwhich allofthe

two-QTL

combinations of thesethree

QTLs

were irrvolved,They revealed

the

non-additive manner of these

QTL

actions on

heading

datefrom

these

advancedrnaterials.

Ina statistical analysis for_quantitativevariation beforethe

popularizationof molecular markers, many _geneticmodels for

geneactions

_generally

regarded epistatic actions tobenegligible, mainly because of the complexity ef the calculations, and concentrated on the analysis of additive and dominance _gene effects

(Kearsey

and Pooni

1996).

Howeveg the_presentresults

forrice _grainlengthartd alsotheresults forriceheadingdate

(Lin

etal.

2000)

obviously

demonstrated

that

interactions

betweentwo

QTLs,

and also a

QTL

and a major

_gene,

concerned with the

same traitshould not

be

negligible

factors

in

_genetic

models fbr

quantitative

traits.Inewery

_year

of the_presentstudy,themean

absolutevalues across allinteractionswere

_.about

halfof thoseof

the

main effects, Moreover,the

_QTL-by-QTL

interactionsmight

havesome conuibution totheinstabilityofcharacter expression,

This impliesthe interactionsamong

QTLs

should _play an

importantand fundamentalrole intheregulation of _quantitative traits.Interactionsinhigherorders among more thantwo

QTLs,

as well as

QIL-by-QTL-by-environment

interactions,should be

evaluated using more advanced NrLs with long-grain

alIeles

in comblnations ofmore thantwe

QTLs,

by

further_pyramidingof

QTLs.

Acknowledgements

The

author expresses special thankstoM.

inoue

and S.Senami,

Schoolof Bioresources,HiroshimaPrefecturalUniversity,and T.

Ybshida,A, ekamoto, T.Kakiuchi,and A.Horibata,Facultyof

Biology-OrientedScienceand [Ibchnology,KinkiUniversity,for

theirvaluable technicalassistance.

References

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C,,

YL

Xing,

H.

Mao.

T.

Lu,

B.Han

C.

Xu, X Liand

Q,

Zhang

(2006)

GS3.

amajor

QTL

for_grainlengthand weight

andminor

QTL

for_grainwidth and thicknessinrice,encodes a

putativetransmembraneprotein.

Theor.

Appl.

Genet.

112

:

1164

-

1171,

Kato,T,

₍₁₉₉₇₎

Inheritanceofgrainsize

in

rice.

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The Society of Crop Science and Breeding in Kinki, Japan

The 　Sooiety 　of _{Crop 　Soienoe}and 　Breeding _{in 　Kinki}

厂

_Japan

J

．

Crop　Res

．

55

　（

2010

）

イ

ネ

の

粒

長

に

関 す

る

QTL

の

主効

果

お

よ び

2QTL

間 相 互

作

用

に

関 す

る

準

同

質

遺 伝 子

系

統 を

用

い

た解 析

加 藤 恒 雄 近 畿 大 学 生 物 理工学 部 （〒

649 − 6493

和 歌 山 県 紀の川 市 西三谷

930

） 要旨：イ ネ 大 粒_品種

‘

BG 　1

’

の粒 長を制御 する 5個の粒 長

QTLs

を対象とし

，

量 的 形 質の

一

モ デル と しての粒 長 に 対 す る 個々の

QTL

の主 効 果 （相 加 効 果 ） お よ び2QTL 間の相互 作 用 （エ ピ ス タ シ ス_{効 果 ）}

，

さ らに大粒 品種

‘

房 吉

’

由来長 粒 型 主 働 遺

r

＝子　Lkfの主 効 果と上 記

QTLs

との相 互 作 用 を 解 析 した

．

その た め

，

同

一

の遺 伝 的 背 景 （品 種

‘

銀坊主

’

）を もつ _合計21_種類の準 同質 遺 伝子 系 統お よび銀坊主 を 用い て

，

2007年と2008年 （L_げに関 する_NILsは

2007

年のみ）に 圃 場 栽 培 して得 ら れ た 粒 長のデ

ー

タ を も と に上 記の主 効 果 と相 互 作 用 を推定した

．

そ の結 果

．

主効 果はLkfが最 も大き かっ たが

，QTLs

間でも有 意な変異 が み ら れ

，

　Lkfに 匹 敵 す る 主 効 果 を示 す

QTL

も存 在し た

．

さ らに

，

主効 果の程 度に 関する

QTLs

問の順序は年 次が異 なっ て もほ ぼ変わ らず

，

主効果の発現程 度は安 定している といえ た

．一

方

，

2QTL 問 相互作 用は ほ と ん どの_{場 合 負}の値と なり

，

組み合わ せ間で大 き く異 なっ た

．

さ らに

，

相互作用の発現程度 は年次 間 で 変 動していた

．

この よ_うに

，

QTL

間 相 互 作 用 は 量 的 形質の_{発 現}に 重要な役 割を果た し

，

特に形 質発 現の不 安 定性の

一

因 になっ てい ると推 察さ れた

．

キ

ー

ワ

ー

ド：イ ネ

，

主効 果

，

相互作 用

，

粒 長

，

量 的形 質 遺伝 子座 　 　 　 作 物 研 究 55：33

−

38_（2010_）