26
SEED TESTING INTERNATIONAL   www.seedtest.org
RULES DEVELOPMENT •
showed 37% fresh seed on average in the two 
laboratories for the standard germination 
method, 8% for the preheating method, 16% 
for the prechilling method and 5.5% for the 
ethephon method. The same observations were 
made for lot H10, although the seeds were less 
dormant.
On average for the two lots with dormancy, the 
ethephon method gives similar results to the 
preheating method and significantly better 
results than the prechilling method.
Repeatability and reproducibility estimates are 
presented in Table 2. The dispersion factor is 
below 1 only for the ethephon method, indicating 
good repeatability of the results obtained with 
this method when dormancy is observed. 
Repeatability is therefore better than for the 
other two methods of dormancy breaking.
Conclusion
This study shows the value of adding the 
dormancy-breaking method using ethephon seed 
treatment to the ISTA Rules. When dormancy 
was observed, two laboratories demonstrated 
the effectiveness of the ethephon method. This 
method is just as effective as the preheating 
method and better than the prechilling method. 
Across all lots and laboratories, the ethephon 
method was found to be as effective as the two 
official methods for dormancy breaking.
Given the preliminary studies showing 
the effectiveness of the ethephon method 
(Ducournau and Dupont, 2023, 2024), especially 
on highly dormant sunflower seed samples, 
we propose to add this new method to the ISTA 
Rules.
Acknowledgements
We gratefully acknowledge seed companies 
Limagrain and Corteva for supplying the seed 
lots.
Many thanks to all the laboratories that 
participated in this validation study and 
thanks to the reviewers from ISTA Technical 
Committees. Thanks to Jean-Louis Laffont 
(ISTA Statistics Committee) who helped run the 
data and for the support he gave in statistical 
interpretation.
References
1.	Corbineau, F., Xia, Q., Bailly, C. and El-
Maarouf-Bouteau, H. (2014). Ethylene, a key 
factor in the regulation of seed dormancy. 
Frontiers in Plant Science, 5.
2.	Ducournau, S. and Dupont, A. (2023). 
Dormancy breaking methods for sunflower 
seeds. Reports of the ISTA Annual Meeting, 29 May 
– 1 June 2023, Verona, Italy. International Seed 
Testing Association, Wallisellen, Switzerland.
3.	Ducournau, S. and Dupont, A. (2024). 
Dormancy breaking methods for sunflower 
seeds. Reports of the ISTA Annual Meeting, 1–4 
July 2024, Cambridge, UK. International Seed 
Testing Association, Wallisellen, Switzerland.
4.	Maiti, R.K., Vidyasagar, P., Shahapur, S.C, 
Ghosh, S.K. and Seiler, G.J. (2006). Development 
and standardization of a simple technique 
for breaking seed dormancy in sunflower 
(Helianthus annuus L.). Helia, 29(45), 117–126.
Figure 3. Boxplots for the four methods per dormancy seed lot (lot H7 and lot H10) and grouped by laboratory on fresh seed
Table 2. Repeatability and reproducibility of the different methods, without laboratory E
Method
Mean
s_Repeatability
Disp
S_Reproducibility
s_Lab
s_Lot × Lab
ETHREL
85
2.84
0.79
10.20
8.50
5.26
PRECHILLING
81
4.38
1.12
6.19
4.88
2.21
PREHEATING
85
4.09
1.14
2.89
0.00
0.00
SD
73
5.48
1.23
10.63
8.93
4.27

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