7/21/2019 Rale-2.1.5b Gjuric & Smith seed size selection.pdf

1/4

R.

Grunrcr and

S.

R.

Snrrrs

Jn r

r

Deutsche

Saatveredelung.

eissenburger

tr 5.

D-59557 Lippstadt,

Germany; Departmentof Plant

Science. niversity

of Manitoba.

Winnipeg.

Manitoba.

Canada.

R3T 2N2

With

2 rables

Ret'eired

Octoher2l

,

l996iAcr:epted

pril

24, 1997

Communicuted

y W. E. Weber

Plant Breeding

16,

337-340

(1997)

|c.;

1997

Blackwell Wissenschafts-Verlag.

erlin

ISSN

0t19-9541

Inheritance

n

seedsize

of alfalfa:

Abstract

Seed ize n alfalfa

Medic'aoo

atfuu

.) hasbeen

ositively

orrelated

with

seedling igour

tnd early

growth.

but thercwcre ew

publishcd

reports n nh eritance

r select ionor

this rait .Theobject ivef this

research as

o estimate

omponents

f

genetic

ariance or nheritirnce

of alfalfa

seed ize nd

determinehe most

efficient election ethod.

Components

f

genetic

ariance

ere

estimatecln seed nd

pollen

plants

f

BIC-7-WH'

and heir

progeny

rrangedn a NorthCarolina

Design

l mating

design nder

ontrolled

nvironmentalondit ions.

Threeselectionmethods, ifl-eringn parental ontrol and selection

pressure,

ere

used o determine

elect ionesponse.he

seed

arent

genotype

ad

a major role

n determinin-q

lfalfaseed ize.but the

genotype

f the

seed adno nf lucnce.

or

genetic

tudies,

ollen

nd

seed

arent

ffects n seed

ize hould

emeasurecln seed arvestcd

from

progeny

lants.

eed izewas

controlled

y addit ivc nd

non-

addit ive omponents

f

genetic

ariance.

eritabil i tybr

seed ize

wa s

41.3%.

elect ionor seed ize

'as f fect ive

nd a signif icanthif t or

larger ndsmaller

eed uas

ttained f ier

one ycle f select ion.

Key words:

Medit'utto

sutit 'u heritability

seedsize selec-

t ion methodology

The relat ionships

etween

lfalfaseed

ize, eedling igour.an d

subsequent

orage

yield

have

stimulzrted

onsiderableesearch

interest

over

the

past

50

years.

Black

(1959)

concluded hat

early

growth

and development

as elated

o seed ize or most

agricultural

plants.

but harvestable

ield

often

was not. A high

correlation

between

seedsizeand

seedling igour was reported

in

alfalfa

(Beverid_ee

nd Wilsie

1959),

and the advantageof

larger

seed ncreased

ith seeding

epth

Erickson

1946).Other

researchers

ave

suggested nly

a weak relat ionship

between

seed

izeand seedling igour

(Nel

and Burgers1968),

nd

that

the relat ionship

dirninishedwith

plant

age

(Smith

1961).

Car-

nahan

(1963)

ound

a

posit ive

correlat ion

between llalfa seed

weight

and

unifoliate eaf

area. and

unifoliate eaf area and

seedlin-seight

at

4weeks.

but there

was

no

direct correlat ion

betu'een eed

sizeand seedling

eight. Despite

he

interest n

alfalta

seed ize, herehas

been int ited

esearch n the

genetic

control of

this trait , and

no reports

on the

select ion esponse

for seed

ize.

There

have been reports

ndicat ing

a response o select ion

for seed

ize n other

herbage egumes.

n three

cycles

f selec-

t ion for

lar-ee eed n

birdsfoot

treloil

(Lotu.s

'ornic'ulatus

.)

the average ainper

cycle anged

between

%,and

20%

(Draper

and Wils ie1965).

Previous genetic

studies

on

alfalla seed size relied on

measurements

aken

on seedharvested

rom the seed

parent

plant

involved

n the crossing

design,

which

may harve

iased

Quantitative

analysis

and

response

o selection

the results. The

strong seed

parent

effect

and

inconsistent inf lu-

ence of

the

pollen parent

suggests

hat

genetic

expressron

for

seed s ize may

need to be measured

on the seed developed on

the

progeny plants.

The object ive o l ' th is resezrrch

as to est i mate the components

of

genetic

variance

involved in

the

inherit i ince

of a lfa lfa

seed

size.

In

addit ion, three select ion

rnethods were applied or-ra

ref-erence

opulat ion

to determine t he most eff ic ient select ion

method to increase

alfa lfa seed s ize.

Materials

and

Methods

Plant

materia ls:

he re lerence

opulat ion

br

th is study was

BIC-7-

WH'

(Barnes

et

al.

1977).

r broad-based

germplasm

developed

or

expcrirncntal

urposes

t USDA-ARS

Research

tat ions n Beltsv i l le ,

Ma rv la n d .a n d S t Pa u l .M in n e s o ta .

S A.

Cult ivat ion: Growth-room condit ions were l8 h l ight

( :400

nrEimr.s)16 dark. 25

C

I t3

C.

I

5 35oA elat ivehumidity

( l ightrdark.

respectively).

reenhouse ondit ionsweresetat constant22

t

2

C

wi th

addit ional

igh t

to lTh

when

needcd.

Growin-rr edium was composed

of

soi l , sand.

peat

and metromix

(W.

R.

Grase& Co.

Ltd..

Winnc'pcg

Canada)

2 : l : l : 1

b y v o lu rn e )n

0 .5 lm i l k - c a r to n s. l a n tswe re n i t i a l l y

f c r t i l i z e d

i th

4 g NPK

(1 0 :4 8 :0 )

e r

l l o f

g ro w in g

me d iu m.and

ate r

w i th a d d i t i o n a l o lu b lcNPK (1 0 :2 0 :0 m ic ro n u t r i e n ts ) m l , i lwa te r

every

3 weekswhile

watering.Thrips

and spidcrmitcs wcre contro l lcd

by spraying Decisr\ l

(AgrEvo

Canada Inc.. Regina.

Canarda)

or

TrumpetrM

NOR-AM

ClhemrcalClo.. ihnington.DE.

USA)oncc

pe r

week.Plantswere

cut at 507obud stage nd crossingwas

done

on the

second

egrowth

o ensurebetter lowering

synchronizat ion.

verage

generation

vcle

ncluding

one

regrowthwas l9

weeks.

Poll inat ion:Contro l led

crossing

was

perfbrmed

using

vacuum

emas-

culat ion. with

t l ie \racl lu ln ube ster i l izedwith 967o ethanol between

two crossings. o l lenwas

collected nd appliedwith fb ldedcardboard.

Standard

petal

was

partially

removed.

Open

pollination

was

perforn-red

without cmasculat ion s inga f lat

toothpick. Selipol l inat i on nvol ved

gently

ol l ing raccmcs

etwccn ingers.

Quantitative

analysis: wenty-lbur

plants.

hree sets

of

four

pollen

an d

four seed

parents.

were randornly

selcctcd

iom

an initial

population

of

'BIC-7-WH'and

arrangedn a North

Carol ina

N

C

)

Design

I crossing

design

Hallauer

and Miranda

1988)

uncler

growth-room

concli t ions.

For

each

cross.

hree acemes

:10

flowers)were

cross-pol l inatcd t

f ive crossing ates.

Crossingdateswere usedas repl icat ions. l l seed

produccd

by cross-pol l inat ion asharvested

nd

ndiv idually

measured

through a compLlter

ig ita l mageanalysis

DIA)

systern. ig ita l nrage

processing

ystem

used

or

seed leasuremcntswas designed iround

a

DT-2U71

HSI)

true-colour rame

-qrabber

Data

Translat ion nc..

Marlboro.

N{A.

USA).

Measurementsoflware was lrnageX

(Dr

L.

Lamari;

Departmcnt

of Plant Science. Univers ity ' o1 ' Mzrnitoba.

u S.

oplr ightlearance

'enterrode

tatement:

l l9

9541

l91

,1604

0337

$

14.00' /0

7/21/2019 Rale-2.1.5b Gjuric & Smith seed size selection.pdf

2/4

Grunrc and

Slrtru

338

Winnepeg,

Canada).

Seed

size

was measured

as

he

area of

seed

mage'

Previous

research

ndicated

that a

large sample

size

is required

to

eliminate

seedsize

variability

resulting

rom

the

number

and

position

of: seeds

n a

pod.

pods

on a raceme

and

racemes

n

a

plant

(Gjuric

et

a l. 1993).Sample

size

or

th is research

was

set

at a minimum

of

15 0

sgsds/plant.

Five

full-sib

progeny

plants

per

cross, otalling

240

plants

(3

sets

x

4

females

x

4 males

48 crosses),

ere randomized

n five

replications,

with one

ull-sib

from each

cross

per

replication.

All

plants werecrossed

to

a single

pollen

source

plant

and

also self-pollinated.

Seed

from

individual

full-sib

plants

were

harvested nd

measured

hrough

the

DI A

for

quantitative

genetic

analysis

or seedsize.

The analysis

of

variance

was calculated

with

mean

squares

pooled

over

setsof

parents

as

proposed or t he N.C.

Design

Il

(Hallauer

an d

Miranda

1988).

Additive

and

diallelic

variance,

based

on an

auto-

tetraploid

model

for a factorial

design,

were

calculated

according

to

Wricke and

Weber

1986):

de:2(oi, ,

+

o?)

2i3

x

oi '

i l l

o t o : 6 x o l , l

t 2 l

where

o2o additive

genetic

variance,

o']o

diallelic

(non-additive)

genetic variance,

oi.

:

variance

due to males.

oi

:

variance

due

to

females, nd oip: variance ue to males x females. o eprstasis.nd

no tri- or

tetra-allelic

effect)

were

assumed.

Narrow

sense

eritability

for seed

sizewas

calculated

as :

h'

:

(oto*

l i3

x

4)

(o*

+

o;

+

oi

+

o?)

t3l

q'here

ft:

:

narrow

sense

heritabilitl ' .

or

additive

genetic

variance'

o;

:

digenic

genetic

ariance.

o;

:

environmental

variancedue

to

rep-

lications. and

ol

:

pooled

error

including

environmental

varlance

among

plants

wi th in

repl icat ion.

Standard

error

of the

heritabi l i ty

est imate

was calculated

according

o Hallauer

and

Miranda

(1988).

Statistical

analysis

was

performed

using he

Statistical

Analysis

S.vstem

(SAS

1988)

GLM

procedure.

Response

o selection:

Three selection

methods.

differing

in

parental

control

and selection

pressure.

were

applied on

the

'BIC-7-WH'

germ-

plasm to determine he most efficientselectionmethod to increase ee d

S1 ZC.

The lirst selection

method

allowed

control

over

both the

selected

seed

and

pollen

parents

full

control,

FC) and

utilized

a

10o/o election

pressure

or both

large

and small

seed.One-hundred

and fifty

randomly

selected

lants from

'BIC-7-WH'

were

grown

and

randomly

inter-

crossed

nder

grou' th-room condit ions.

One-hundred

and

twenty

of

the

orig inal

p lants

produced

a

suli lc ient

number

of seed

>

150)

or

subsequent

neasurements

hrough

the DIA

for

seed ize.

Twelve

plants

rvith the

highest tverage

seed

size

were identified

as

the large-seeded

populat ion

LStand

1l

p lantswith the owest

average

eed

ize

as he

small-seeded

opulat ion

(SS) .

These

plants

were

placed

back

in

the

gronth-room

and

randomly '

ntercrossed

wi th in

respective

S

or SS

populat ions

$' i thout emasculat ion.

The second

elect ion

method

allowed

contro l

over

only

the

selected

seed arenrs half contro l. HC) u i th a 1070 elect ion ressureor both

large and small

seed.

he mature

seed

roducedon

the

12 LS

and 12

SS

plants

iom

the nrt ia l

150

lant

ntercross

ereused

or

th isselect ion

method.

For both

LS and SS

populations,

eight

half-sib

progeny from

each

selected

lant (12

x

8:96

plants

per populat i on) were

grown

and randomly

intercrossed

within their

respective

population

under

greenhouse onditions

without

emasculation.

The

third selection

method

was a form

of

mass selection

with

no

control

(NC)

over the

selected

arents

and a

selection

pressure

of

less

than

1%

(based

on weight

of

size separates)

or both

large and

small

seed.

A representative

eed

ot from

'BIC-7-WH'

was mechanically

separated

using

a series

of dockage

screens f varying sizes Seedburo

Equipment

Co.. Chicago.

L. USA).

Twenty-five

plants

rom the

argest

seed

raction

(screen

size

> 1.8mm)

and 25

plants

from the

smallest

seed

raction

(

< 1.0mm)

were

grown

under

growth-room conditions.

Plants

were randomly

intercrossed

withrn

respective

opulations with-

out

emasculation.

The three

selection

methods

produced

he

following

six experimental

populations:

(l)

large seed

ull control

(FC-LS). (2)

small

seed

ul l

control

(FC-SS), 3)

arge

seed

alf control

(HC-LS). (4)

small

seed

al f

control

(HC-SS),

(5)

large

seed

no control

(NC-LS)

and

(6)

small

seed

no

control

(NC-SS).

A

greenhouse

xperiment

o

determine

he

success

of the

different

selection

chemes

as established

sing the

six selected

populations and the

unselected

eference

opulation'BIC-7-WH'.

Th e

experimental

design

or each

population was a

randomized

complete

block

design

RCBD), with nine

replications

and

four

plants

per

plot

(36 total plant per population). The plants were randomly intercrossed

without

emasculation

within

each espective

opulation.

Seed

was har-

vested

and

samples

containing

a

minimum

300 seeds

per

plot

were

measured

hrough

DIA

for seed

size.Seed

weight

was

determined

on a

seed

sample

of 150

seeds

per plot.

Mean

separation

analysis

used

Fisher's

protected

eastsignificant

difference

est.

Results

QuantitatiYe

analysis

Seed

size

measured

on

the

parental

plants

nvolved

n

the

cross-

ing design

was

not correlated

o the seed

size

measured

on the

progeny

plants r

:

0.256

lS, l

:

44).Seed ize

on the

parental

plants was influenced

only

by the

seed

female)

parent

(Table

l). Crossing

dates

were used

as

replicat ions

nd

they

also

ha d

an

influence

on seed

size.

Seed

size on

the

pro-sen)'

lants

(a

single

plant

used as

the

pollen

source)

was

influenced

signifi-

cantly

by

both

the seed

and

pollen

(male)

parent

nvolved

n

the crossing

design,

and also

the

interact ion

betueen

he

tw o

(Table

1). Replications

n this case

were represented

'ith five

full-sibs

and did

not

have a

significant

effect.

Components

of

genetic ariance

estimated

n

parental

plants

had values

of

oi

:0.1292

and oi

:

0'0084

and showed

ha t

only

o2a ad a

significant

role in determining

seed

size,

which

would

be expected

with

a

maternally

inherited

trait.

Despite

this,

narrow-sense

er i tabi l i ty

was

only

23.690

SE:22.1) .

When

seed size

was

measured

on the

progenr.

plants, both

additive

and

non-additive

components

of

genetic variance

appeared

to be

involved

in the

inheritance

of

seed

size

(o2o:0.049

and

o2p 0.049,

respectivel))

and

narrow-sense

her i tabi l i tv

as

41 3%

(SE

15.1) .

Tab le l : ANOVA

table

or a

genetic

study

of alfalfa

seed

size using

North Carol ina

Design

II mating

design

random

model)

and'BIC-7-

WH' usedas

reference

opulatton

Parental

plants

df

MS

Progenl

p lants

d I

MS

EMS

Source

Set

Rep

(se t )

Female

set)

Male

(set)

Female

x

male

(set)

Pooled

error

2

t 2

q

o

21

r 6 1

5 . 571

s

0 . 385

*

I . 4 1 6 * * r