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

Abstract

Sunflower (Helianthus annuus L.) seed industry needs nondormant seeds (i.e., seeds with the capacity to germinate in a wide range of environmental conditions) for processing and packaging. Thus, the presence of persistent seed dormancy is an undesirable trait. Dormancy level depends on the genotype and on the maternal environment. The aim of the present work was to study, in a wide range of sunflower genotypes, the effect of variations in sowing date on achene dormancy level and to investigate if these changes are related to variations in (a) embryo or coat‐imposed dormancy, (b) dormancy expression at high or low incubation temperatures, and (c) embryo sensitivity to abscisic acid (ABA). Two experiments were performed. In Experiment I, 20 sunflower genotypes were sown in two contrasting planting dates during three consecutive years, whereas in Experiment II, 1579 genotype was sown in five dates along a 5‐mo period. At harvest and during postharvest storage, fruit structures were incubated at different incubation temperatures in water and ABA. Descriptive multivariate analyses showed that late sowings provoked an enhancement of achene germination at harvest and a faster dormancy release during postharvest storage in all genotypes. However, the magnitude of the response, the temperature at which dormancy was expressed, and the tissue responsible for achene dormancy varied among genotypes. The mechanism that partially explains this dormancy alleviation appears to be the sensitivity of embryo germination to ABA inhibition. Result suggest that sowing date can be managed to obtain less‐dormant sunflower seed lots without significant yield loss.

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

“…The maternal environment is also known to affect deep dormancy traits in sunflower as first suggested by Bodrone et al (2017) and more recently by Lachabrouilli et al (2021) and Riveira-Rubin et al (2021). In this work, Experiments I and II were sown in a similar date within the growing season, and environmental variables indicate that meteorological conditions were similar in both years (Supplemental Table S1).…”

“…The parameters T l (50), T h (50), and θT (50) values with its standard deviations are exposed in Supplemental Table S2. Observed and calculated germination curves are presented in Supplemental Figure S9 generating different environments) should be considered carefully, as late sowings can significantly reduce dormancy and contrast between genotypes is attenuated (see Riveira-Rubin et al, 2021). Ongoing research by our group also points to the necessity of very strict post-harvest manipulation of ach-enes, as achene moisture content during storage can deeply affect the after-ripening process (Bazin, Batlla et al, 2011).…”

“…However, remaining dormancy levels in modern sunflowers may be due to a shorter domestication history for this species (Radanović et al, 2018), or also because selection pressure did not focus on rapid germination shortly after harvest as in other crops species, where grains are used for malting (e.g., barley [Hordeum L.], wheat [Triticum aestivum]; Barrero et al, 2012;Rodriguez et al, 2015). In addition, strong interactions with the maternal environment (Bodrone et al, 2017;Riveira-Rubin et al, 2021) can make it difficult to track dormancy traits along a breeding programme. Very few works have addressed intraspecific variability for dormancy in cultivated sunflower (Maiti et al, 2006;Subrahmanyam et al, 2002;Vujaković et al, 2012) using different criteria for phenotyping, and a more comprehensive approach is still missing.…”

Transgenerational Genetic Effects Help Explain Latitudinal Variation in Seed Mass and Germination Timing in Plantago lanceolata

“…Many studies have documented genetic variation in seed traits in and among local populations [23,77,106,[113][114][115][116][117][118][119][120]. Parental environment and maternal genotype in P. lanceolata can influence seed mass and germination, as evidenced by both controlled and field experiments [73,77,82,114]. Studies have provided evidence that (1) cool parental temperature increases total seed weight and reduces germination relative to the effects of warm parental temperature [73,82], (2) maternal families differ in thermal response [73,82], and (3) an increase in seed coat mass, but not embryo/endosperm mass, explains the increase in total seed mass at cooler temperature [76].…”

“…Thus, maternal and paternal parents and the zygotic tissues can contribute separately, or interactively, in different ways to seed traits, and contributions could be genetic or environmentally induced. In addition, tissues could differ in their phenotypic plasticity, i.e., in their responses to local environmental change [71][72][73]. The above contributions have evolutionary and conservation implications because only the genetic variation in a trait is available for natural or artificial selection.…”