Effect of storage temperature on dormancy release of sunflower (Helianthus annuus) achenes

Abstract

Published information regarding the effect of storage temperature on dormancy alleviation of sunflower achenes is contradictory and ambiguous. In the present study we explored the effect of temperature during dry storage on dormancy release in two sunflower genotypes, including a commercial hybrid and an inbred line. Dry storage at 25°C consistently accelerated dormancy release of achenes compared with 5°C. This response fits the general pattern reported for dry after-ripening in seeds of many other species. Depending on the genotype and the dormancy factor prevailing, higher temperature alleviated embryo dormancy and coat-imposed dormancy. Hormonal pathways involved in these changes were investigated at the physiological level. In both genotypes, sensitivity to abscisic acid (ABA) was reduced by storage at 25°C. Also, but only in one genotype, storage at 25°C reduced ABA levels upon imbibition and increased the response to a gibberellin (GA) synthesis inhibitor and to applied GA3, compared with storage at 5°C; these results support the idea that temperature affects both ABA and GA metabolism and signalling pathways during after-ripening. This information will be useful to define storage conditions for commercial sunflower achenes, and will also help focus future research on the underlying mechanisms of dormancy release during dry after-ripening in sunflower.

Dormancy attributes in sunflower achenes (Helianthus annuusL.): I. Intraspecific variability

“…This central role of ABA signalling in the embryo is in agreement with previous works by our group (Bodrone et al, 2017;Rodríguez et al, 2018). In these works, embryo responsiveness to ABA was also related to differences in achene dormancy (as affected by the maternal environment or by storage temperature).…”

“…In sunflower, deep-embryo dormancy during achene development depends on active ABA synthesis in the embryo axis (Le Page-Degivry & Garello, 1992). A role for ABA metabolism in achene dormancy at harvest maturity and during postharvest dry storage is less clear and may have a minor contribution only in some genotypes (Rodríguez et al, 2018). Instead, dormancy release during dry storage has been consistently related to a progressive decline in embryo responsiveness to applied ABA (Le Page-Degivry et al, 1996;Rodriguez et al, 2018).…”

“…Although some detailed studies on physiological aspects of dormancy have been conducted in sunflower, most studies are based on a few genotypes, for example, 'Mirasol' (Le Page-Degivry et al, 1989, 1992, 1996Corbineau et al, 1990;Gay et al, 1991;Bianco et al, 1994), and 'LG5665' (Oracz et al, 2008;Bazin, Batlla et al, 2011;Bazin, Langlade et al, 2011). In other works which included at least two genotypes, different responses to growth regulators suggest the existence of variability in dormancy mechanisms among cultivated (crop) sunflowers (Roselló et al, 2016;Bodrone et al, 2017;Rodríguez et al, 2018;Dominguez et al, 2019). Thus, studies over a wider germplasm base are required to understand the basic mechanisms involved in dormancy regulation in cultivated sunflowers.…”

“…It is well known that seed dormancy is a complex, heritable trait, and its intensity at harvest and persistence afterwards depends on the genotype but can also be modulated by the maternal (in the field) and post-harvest (storage) environments (Bazin, Batlla et al, 2011;Bodrone et al, 2017;Finch-Savage & Leubner-Metzger, 2006;Rodríguez et al, 2018). Domestication process has resulted in decreased seed dormancy levels in many crop species (Hancock, 2012;Rodríguez et al, 2015).…”

Dormancy attributes in sunflower achenes (Helianthus annuus L.): II. Sowing date effects

“…(1996) and Rodríguez et al. (2018). Thus, embryo responsiveness to ABA appears as a major factor controlling achene dormancy and appears to be regulated not only by the maternal environment and after‐ripening time, but also reflects intraspecific variability, as shown in Arata et al.…”