24
SEED TESTING INTERNATIONAL   www.seedtest.org
RULES DEVELOPMENT •
A New Method for Breaking Dormancy  
in Sunflower Seeds
Audrey Dupont and Sylvie Ducournau
GEVES, Station Nationale d’Essais de Semences, Beaucouzé, France
THE OBJECTIVE OF THIS STUDY WAS 
TO INTRODUCE A NEW DORMANCY-
BREAKING METHOD WITH ETHEPHON 
TREATMENT to the current ISTA methods 
prescribed for releasing the dormancy of 
sunflower seeds.
Summary
The introduction of this method to the 
International Rules for Seed Testing (ISTA Rules) 
has been suggested by some laboratories in 
France. Immediately after harvesting sunflower 
(Helianthus annuus L.), seed dormancy is 
sometimes very deep and the ISTA methods 
recommended to break dormancy in this species 
(prechilling and preheating) do not overcome 
it completely. In such cases it is impossible to 
assess the full germination potential of the seeds 
through a germination test.
After three years of experiment in France, 
involving two seed companies and four seed 
testing laboratories, we have demonstrated that a 
seed pretreatment with ethephon is an effective 
method to release the dormancy of freshly 
harvested sunflower seeds exhibiting high 
levels of dormancy. Ethephon and ethylene are 
known for their efficacy to break the dormancy of 
sunflower seeds (Corbineau et al., 2014; Maiti et 
al., 2006) but using ethylene gas is not convenient 
in a laboratory.
It was therefore proposed to start a validation 
study in the ISTA Germination Committee, to 
add this method to the current methods already 
prescribed in the ISTA Rules for H. annuus.
Material and Methods 
Seed Material 
Helianthus annuus L. seed lots were supplied 
by two different seed companies, with five seed 
samples from each company. The samples were 
encoded H1 to H10.
Participant Laboratories
A total of seven laboratories participated in the 
validation study. The laboratories were located in 
Germany, Italy, The Netherlands and France.
Germination Methods
All participants in this study compared four 
methods: three dormancy-breaking methods 
including the two recommended ISTA methods 
(prechilling and preheating) and the new 
method proposed with ethephon, as well as the 
standard germination test to assess the initial 
dormancy of seed lots.
• Method 1 (SD): ISTA germination test with no 
dormancy treatment
• Method 2 (PREHEATING): ISTA germination 
test after preheating
• Method 3 (PRECHILLING): ISTA germination 
test after prechilling
• Method 4 (ETHREL): ISTA germination test 
after ethephon treatment
The ETHREL method is as follows: the seeds are 
soaked in a 0.3 g/l (300 ppm) active ingredient 
ethephon solution for 18 h (±1 h) at room 

View this content as a flipbook by clicking here.