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

Abstract

Cultivated sunflowers (Helianthus annuus L.) display variable degrees of achene dormancy at harvest and persistence during storage, interfering with high-quality hybrid seed production. Information on intraspecific variability for dormancy among cultivated sunflowers is scarce and was the subject of this work. A set of 21 sunflower genotypes of diverse origins (18 crop and 3 wild) was used for phenotyping dormancy traits. Experimental data included achene and embryo germination at different incubation temperatures, in water or abscisic acid (ABA), and different storage times postharvest. Multivariate analyses produced dormancy groups differing mostly in their patterns for dormancy expression along the thermal range and their dormancy release rate. The observed variability was interpreted as resulting from the overlap of two mechanisms: low temperature-expressed dormancy (LTED), common to all genotypes; and thermo-inhibition (TI) at high incubation temperatures, exclusive to some genotypes. Embryo responsiveness to ABA varied among genotypes and was positively related to LTED and TI, supporting that both responses share a common regulatory pathway operating in the embryo. We show that there is considerable intraspecific variability for dormancy attributes among cultivated sunflowers.

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

“…A decrease in ABA responsiveness in accordance to a lower dormancy level as a result of variation in the environmental conditions explored by seeds during their development and maturation has been previously reported in other species (Benech-Arnold et al, 1991, 1995Contreras, 2007) and suggested for sunflower (Bodrone et al, 2017). In addition, embryo sensitivity to ABA was also related to changes in achene dormancy level during dry storage, as was observed in Arata et al (2021) and reported previously by Le Page-Degivry et al (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 (2021).…”

“…For LMA and BAR (wild genotypes), germination values were lower at 25 than 10 ˚C and remained below 30% in both sowing dates even after 150 d of storage. These wild genotypes exhibit strong thermo-inhibition, as shown in Arata et al (2021).…”

“…The opposite occurred in 1579 genotype (Figure 5B; Supplemental Figure S4; Supplemental Table S6), in which the wider range in late sowings was a consequence of a higher mean T h [T h (50)]. This suggests that this genotype loss the TI documented in Arata et al (2021) with the delay in the sowing date. Wild population AAL (Figure 5C; Supplemental Figure S4; Supplemental Table S6) increases the thermal range when cultivated in late sowings either through a lower T l (50) and higher T h (50).…”

“…Effect of sowing date on embryo responsiveness to ABA: Experiment II Embryo responsiveness to the inhibitory effect of ABA decreased both with storage time (accompanying achene dormancy release, as shown in Arata et al, 2021) and with the delay in the sowing date (Figure 4). However, embryos from the January sowing presented a significant lower sensitivity to ABA than embryos from the earlier sowings.…”

“…Intraspecific variability for dormancy mechanisms was the subject of Arata et al (2021), in which different dormancy attributes were measured in a set of diverse sunflower genotypes. Results showed that tested genotypes present two different thermal expression responses: low temperature-expressed dormancy (LTED) and thermoinhibition (TI).…”