pre-breeding research in onion: screening an onion

Pre-breeding research in onion:

screening an onion diversity set

for beneficial traits

Dr Andrew Taylor

Research Fellow

http://www2.warwick.ac.uk/fac/sci/lifesci/wcc/

http://www2.warwick.ac.uk/fac/sci/lifesci/

Project objectives

• Screen an onion diversity set and develop

a further understanding of the genetic

control of:

1. Resistance to Fusarium oxysporum

2. Response to AMF

3. Seed and seedling vigour traits

Onion diversity set

• 96 accessions sampled from the Warwick Crop

Centre Genetic Resources Unit

• Including LD, ID and SD cultivars

• Includes A.roylei, A.vavilovii and A.fistulosum

• Seed produced for 10 half sib families for each

accession

• DNA extracted from 1 half sib family per

accession

Owa Greenella White Sweet Spanish Jumbo

Auxonne Red Wetherfield The Kelsae

Moravanka Sarand Rossa di Firenze

Guardsman

www2.warwick.ac.uk/fac/sci/lifesci/research/vegin/onion

Fusarium basal rot

• Fusarium oxysporum f. sp. cepae is a

soilborne fungus causing basal rot in onion

• Found on onions throughout the world

• Currently one of the biggest problems for UK

onion growers and set producers

• Likely to become a greater problem with

current climate change models

• Can cause damage at every stage of plant

development


Symptoms of basal rot


Screening for resistance to

Fusarium oxysporum

• Glasshouse based seedling screen developed

• Seeds soaked in a spore suspension for 1

hour prior to sowing

• Plant death scored over a 4 week period

• Glasshouse based screen on mature plants

developed

• Involves transplanting seedlings into

Fusarium-infested compost

• Two tests produce comparable results


Seedling screen



Resistance in commercial

onion cultivars

0

10

20

30

40

50

60

70

80

90

Perc

en

tag

e s

urv

ival

Taylor et al. 2012, Plant Pathology, in press

10

20

30

40

50

60

70

80

90

Re

lati

ve

su

rviv

al

(%)

Line

Susceptible control Partially resistant control

Resistance in the diversity set


Confirming resistance- mature plant screen


0

10

20

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40

50

60

70

SD 1 SD 2 SD 3 SD 4

Pla

nt

death

(%

)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

SD 1 SD 2 SD 3 SD 4

Mean

sym

pto

m s

co

re

+ 6 plants dead prior to harvest

Confirming resistance- mature plant screen


Arbuscular Mycorrhizal Fungi

(AMF)

• Colonise roots and help increase nutrient

uptake

• Can increase yield, improve resistance to

pathogens and increase drought tolerance

• Onion diversity set screened for mycorrhizal

responsiveness

2. Response to AMF

Screening the diversity set

for response to AMF

2. Response to AMF

• Glasshouse based trial

• Irradiated field soil (low P) inoculated with a

single AMF species

• Onion seedlings transplanted into inoculated

soil

• Growth and nutritional responses recorded

after 10 weeks

• 15 lines tested in low and high P

50

55

60

65

70

75

80

85

90

95

Myco

rrh

izal

dep

en

den

cy (

%)

Highly responsive

Lower response

Screening the diversity set

for response to AMF

Onion line

2. Response to AMF

Growth effects

Control Inoculated

Control Inoculated

Highly responsive Lower response

2. Response to AMF

2. Response to AMF

0

0.2

0.4

0.6

0.8

1

1.2

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2

control low P control high P Inoc low P Inoc high P0

0.2

0.4

0.6

0.8

1

1.2

1.4

control low P control high P Inoc low P Inoc high P

0

0.5

1

1.5

2

2.5


0

0.2

0.4

0.6

0.8

1

1.2

1.4


High P vs. low P

Seed/seedling vigour

• Important for crop establishment and

uniformity

• Tests developed based on Brassica work (Bill

Finch-Savage, Warwick University)

• Diversity set screened for seed/seedling vigour

• Two tests of vigour- germination/initial growth

rate and emergence in compact soil

3. Seed/seedling vigour

70

90

110

130

150

170

190

210

Tim

e f

or

roo

t to

reach

3cm

(h

rs)

Onion line

Screening the onion diversity

set for seed/seedling vigour

3. Seed/seedling vigour

Is there a correlation between

vigour and Fusarium

resistance?

R² = 0.1762

50

70

90

110

130

150

170

190

0 20 40 60 80 100

Tim

e f

or

roo

t to

reach

3cm

(h

rs)

Fusarium resistance (% survival)

Summary and current work

• Onion diversity set developed and screened for

agronomically important traits

• Sources of Fusarium resistance identified

• Different levels of response to AMF observed

• Highly vigorous lines identified

• Current work:

Confirming sources of Fusarium resistance

Genotyping the diversity set using SNP

markers

Acknowledgments

VeGIN project:

• Dave Pink

• Brian Thomas

• John Clarkson

• Gary Bending

• Paul Hand

• Nicole Pereira

University of

Wisconsin:

• Mike Havey

University of Warwick:

• Andrew Mead

• Julie Jones

• Viktoria Vagany

• Andy Jukes

• Matthew Mitchell

• Joan Yurkwich

www2.warwick.ac.uk/fac/sci/lifesci/research/vegin/onion

[email protected]

• Warwick Crop Centre GRU & Horticultural Services

pre-breeding research in onion: screening an onion

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