Effects of agroclimatic conditions on sunflower seed dormancy at harvest

Abstract

At harvest sunflower seeds (Helianthus annuus L.) are dormant and poorly germinate at 10 and 25 °C. Seed sensitivity to low temperatures (10 °C) results from an embryo dormancy whereas the envelopes (pericarp and seed coats) inhibit the germination at 25 °C. Removal of pericarp greatly improved seed germination when the germination of whole achenes was higher than the critical value of 20 %. Using 107 seed batches corresponding to 26 genotypes cultivated in 2015, 2016 and 2017 in various production areas in France (Center and South) and Spain (South), we investigated the effects of agro-environmental factors on the depth of dormancy at harvest. A principal Component Analysis (PCA) performed with all the seed batches did not show any significant effect of the genotype (variety or female) and year of production on the intensity of dormancy, but it revealed the role of agro-climatic conditions. Experimental field trials performed with plants treated by a chemical desiccant after flowering demonstrated that accelerated desiccation during seed maturation on the mother plant was associated with lower dormancy. Our data also suggest that the longest the duration of the developmental cycle from sowing to harvest, the lowest the dormancy at harvest. We provide new insights into the modulation of dormancy intensity by genetic and environmental factors which might have practical applications in seed production.