Universität Hohenheim

Division of Seed Science and Technology

Storability of ultra dry

wheat, rape and onion seeds

M. Kruse and Q. Yang

Outline of the presentation

Introduction Definition of ultra-dry seed storage

Objective of the present study

Material and Methods Seed material, drying, storage,

germination tests, determination of r.H. and M.C.

Results Sorption isotherms

Probit lines for germination loss during storage

slope of the probit lines as depending on M.C.

optimum M.C. for ultra-dry seed storage

Conclusions

Definition of ultra-dry seed storage

Ultra-dry seed storage is the approach

„... to maximise the benefit of desiccation to

subsequent longevity by drying seeds

to 10 – 12% r.h. at 20°C and then storing

hermetically at ambient, but preferably cooler

temperatures, ...“

FAO/IPGRI Genebank Standards 1994

No artificial cooling is required during long term storage, which may

improve storage security in low cost environments.

Experimental proof of ultra-dry seed storage:

The Vienna Oat Sample of 1877

Storage experiment started on 25 Nov. 1877

by Prof. Dr. Haberlandt, BoKu University Vienna

- Avena sativa: 97% germination and 3.14% M.C.

- 110 years in the cellar

of the University building at about 15 °C

- final germination: 81%

Seeds of other species as impurities also

germinated (Hordeum vulgare, Vaccaria

hispanica, Agrostemma githago, …)

Steiner and Ruckenbauer (1995)

The objectives

1. Is there a consistent upper limit of moisture

content for ultra-dry seed storage?

2. Is there a lower limit? Can seeds be over-

dried?

3. Is the seed viability equation applicable in

the ultra-dry range?

Seed material

Commercial seed lots

3 samples of wheat (Triticum aestivum L.)

(Tommi, Naturastor, Triso)

2 samples of rape seed (Brassica napus L.)

(A, B)

2 samples of onion (Allium cepa L.)

(Giugenese, Sturo)

different in oil content and in storability

Methods

- Determination of M.C. according to ISTA Rules

- Drying of sub-samples to between nearly 0% and

about 7 % above silica gel

- Sealing in aluminum foil packages

- Storage at 50 °C for up to 1 year with regular

removal of sub-samples

- Determination of r.H. with Tesa 645 in the

packages

- Opening of the packages, equilibration of seeds

to ambient conditions

- Germination tests according to ISTA Rules

- Calculation of sorption isotherms and probit lines

for germination loss

Sorption isotherms for wheat

according to the model of Henderson (1952)

0

2

4

6

8

0 10 20 30 40

r.H. (%)

M.C

. (%

)

Naturastor

Tommi

Triso

Sorption isotherms for rape seed

according to the model of Henderson (1952)

0

1

2

3

4

5

6

7

8

0 20 40 60 80

r.H. (%)

M.C

. (%

)

A B

Sorption isotherms for onion

according to the model of Henderson (1952)

0

1

2

3

4

5

6

0 5 10 15 20

r.H. %

M.C

. %

Giugenese

Sturo

0

10

20

30

40

50

0 20 40 60 80 100

r.H. %

M.C

. %

Herderson ModelSturo

Henderson ModelGiugenese

Germination of winter wheat cv. Naturastor

during storage at 50 °C

0

20

40

60

80

100

0 100 200 300 400

Storage duration (days)

Germ

inati

on

(%

)

3.18

1.24

0.34

-2

-1

0

1

2

3

0 100 200 300 400

Storage duration (days)

Germ

inati

on

(p

rob

it)

3.18

1.24

0.34

Moisture

content (%)

Moisture

content slope

-0.0067

-0.004

-0.012

Slopes of the probit lines for two rape seed lots

during storage for one year at 50 °C

-0,1

-0,08

-0,06

-0,04

-0,02

0

0 2 4 6 8 10

mc (%)

slo

pe

(p

rob

it/d

)

A

B

Constants of the seed viability equation:

Ellis et al. (1989)

slope according to

the seed viability

equation

Slopes of the probit lines for two rape seed lots

during storage for one year at 50 °C

-0,1

-0,08

-0,06

-0,04

-0,02

0

0 2 4 6 8 10

mc (%)

slo

pe

(p

rob

it/d

)

A

B

Constants of the seed viability equation:

Ellis et al. (1989)

slope according to

the seed viability

equation

y = 0,12 - 0,06x + 0,0072x²

R² = 0,991

y = 0,017 - 0,0072x + 0,0009x²

R² = 0,876

optimal

M.C.

Slopes of the probit lines for three wheat seed

lots during storage for one year at 50 °C

-0,025

-0,02

-0,015

-0,01

-0,005

0

0 1 2 3 4 5 6

mc (%)

slo

pe

(p

rob

it/d

)

Triso

Naturastor

Tommi

slope according to

the seed viability

equation

Constants of the seed viability equation:

Hong et al. (1996)

Slopes of the probit lines for three wheat seed

lots during storage for one year at 50 °C

-0,025

-0,02

-0,015

-0,01

-0,005

0

0 1 2 3 4 5 6

mc (%)

slo

pe

(p

rob

it/d

)

Triso

Naturastor

Tommi

slope according to

the seed viability

equation

Constants of the seed viability equation:

Hong et al. (1996)

optimal

M.C.

Slopes of the probit lines for two onion seed

lots during storage for one year at 50 °C

-0,025

-0,02

-0,015

-0,01

-0,005

0

0 1 2 3 4 5 6

mc (%)

slo

pe

(p

rob

it/d

)

Giugenese

Sturo

slope according to

the seed viability

equation

Slopes of the probit lines for two onion seed

lots during storage for one year at 50 °C

-0,025

-0,02

-0,015

-0,01

-0,005

0

0 1 2 3 4 5 6

mc (%)

slo

pe

(p

rob

it/d

)

GiugeneseSturo

slope according to

the seed viability

equation

optimal

M.C.

Conductivity of rape seed

during storage at 50 °C

0

50

100

150

200

250

300

350

0 2 4 6 8

Seed moisture content (%)

Co

nd

uc

tiv

ity

(m

icro

Sim

en

s /c

m*g

)

0

2

5

8

Storage period

(months)

Optimum ultra dry seed storage conditions

Species optimal optimal initial germination after

lot M.C. (%) r.H. (%) germination 1 year at 50 °C

(%) (%)

Wheat

Naturastor 2.3 10.9 95 85

Triso 2.0 6.0 95 88

Rape seed

A 4.0 41.7 95 93

B 3.1 20.6 95 94

Onion

Giugenese 2.7 2.1 95 75

Sturo 1.9 4.6 95 72

Conclusions

1. The upper limit of moisture content for ultra dry seed storage varies among

the tested species, on the level „moisture content“ as well as on the level

„relative humidity“.

2. These differences are also relevant for the determination of optimum seed

moisture content or r.H. for ultra-dry seed storage.

3. Seeds can be overdried for ultry dry seed storage. There was a significant

lower storability in all species, when seed moisture content was below 2 %.

4. The seed viability equation overestimated storage potential of ultra dry (and

over dried) seeds.

5. Based on the obtained data it may not be possible to give a general

recommendation for the optimum range of M.C. or r.H. for ultra-dry storage.

Universität Hohenheim

Division of Seed Science and Technology

Thank you for your attention

Michael.Kruse@uni-hohenheim.de