Maternal control of early life history traits affects overwinter survival and seedling phenotypes in sunflower (Helianthus annuus L.)

Abstract

When cultivated and wild plants hybridize, hybrids often show intermediate phenotypic traits relative to their parents, which makes them unfit in natural environments. However, maternal genetic effects may affect the outcome of hybridization by controlling expression of the earliest life history traits. Here, using wild, cultivated and reciprocal crop–wild sunflower (Helianthus annuus L.) hybrids, we evaluated the maternal effects on emergence timing and seedling establishment in the field and on seedling traits under controlled conditions. In the field, we evaluated reciprocal crop–wild hybrids between two wild populations with contrasting dormancy (the high dormant BAR and the low dormant DIA) and one cultivar (CROP) with low dormancy. Under controlled conditions, we evaluated reciprocal crop–wild hybrids between two wild populations (BAR and RCU) and one CROP under three contrasting temperature treatments. In the field, BAR overwintered as dormant seeds whereas DIA and CROP showed high autumn emergence (~50% of planted seeds), resulting in differential overwinter survival and seedling establishment in the spring. Reciprocal crop–wild hybrids resembled their female parents in emergence timing and success of seedling establishment. Under controlled conditions, we observed large maternal effects on most seedling traits across temperatures. Cotyledon size explained most of the variation in seedling traits, suggesting that the maternal effects on seed size have cascading effects on seedling traits. Maternal effects on early life history traits affect early plant survival and phenotypic variation of crop–wild hybrids, thus, they should be addressed in hybridization studies, especially those involving highly divergent parents, such as cultivated species and their wild ancestors.

Rapid evolution of seed dormancy during sunflower de-domestication

“…Due to its crucial ecological role and its early expression in the life cycle, seed dormancy is expected to be under especially strong selection (Huang et al, 2010). Therefore, we recently reconstructed the genetic background of BRW by crossing a CROP as the female with BAR as the male and we observed an overall low seed dormancy with cascading effects leading to high autumn emergence, low overwinter survival, and poor establishment in the field (Hernández et al, 2021). This indicates that if genetic variation is present, selection against low dormant phenotypes can be strong.…”

“…Although this approach does not distinguish selection from genetic drift or gene flow (Franks et al, 2018), we gathered evidence in favor of selection. Firstly, the phenotype changed in the predicted sense, towards higher seed dormancy (Darmency et al, 2017; Hernández et al, 2021; Presotto et al, 2020). Secondly, the census size of both ancestor and descendant biotypes (>10,000 individuals) and the effective population size of the descendant biotype (inferred through genetic markers) are very large, minimizing the influence of genetic drift on phenotypic evolution (Kreiner et al, 2018).…”

“…Secondly, the census size of both ancestor and descendant biotypes (>10,000 individuals) and the effective population size of the descendant biotype (inferred through genetic markers) are very large, minimizing the influence of genetic drift on phenotypic evolution (Kreiner et al, 2018). Thirdly, although gene flow between weedy and cultivated sunflower probably occurred in the time frame between the collections, the cultivated sunflower showed mostly no, or low, dormancy (Hernández et al, 2017(Hernández et al, , 2021 and the weedy traits changed in the opposite direction, i.e. dormancy evolved despite, rather than aided by, gene flow.…”

“…Among these traits, seed dormancy and herbicide resistance are among the most important for the successful establishment of weeds. Seed dormancy plays a crucial ecological role, contributing to avoidance of out of season germination (Presotto et al, 2020; Hernández et al, 2021), and persistence in soil seed banks (Darmency et al, 2017; Pipatpongpinyo et al, 2020; Presotto et al, 2020). On the other hand, the high killing rates associated with herbicide applications exert strong selection pressure for herbicide resistance (Darmency et al, 2017; Kreiner et al, 2018; Tranel and Wright, 2002).…”

“…Seed dormancy plays a crucial ecological role, contributing to avoidance of out of season germination (Presotto et al . 2020; Hernández et al . 2021), and persistence in soil seed banks (Darmency et al .…”