Roles of maternal effects and nuclear genetic composition change across the life cycle of crop–wild hybrids

Abstract

• Premise of the study: The fi tness of an offspring may depend on its nuclear genetic composition (via both parental genotypes) as well as on genetic maternal effects (via only the maternal parent). Understanding the relative importance of these two genetic factors is particularly important for research on crop-wild hybridization, since traits with important genetic maternal effects (e.g., seed size) often differ among crops and their relatives. We hypothesized that the effects of these genetic factors on fi tness components would change across the life cycle of hybrids. • Methods: We followed seed, plant size, and reproductive traits in fi eld experiments with wild and four crop-wild hybrids of sunfl ower ( Helianthus annuus ), which differed in nuclear genetic composition and maternal parent (wild or F1 hybrid).• Key results: We identifi ed strong genetic maternal effects for early life cycle characteristics, with seeds produced on an F1 mother having premature germination, negligible seed dormancy, and greater seedling size. Increased percentages of crop alleles also increased premature germination and reduced dormancy in seeds produced on a wild mother. For mature plants, nuclear genetic composition dominated: greater percentages of crop alleles reduced height, branching, and fecundity.• Conclusions: Particular backcrosses between hybrids and wilds may differentially facilitate movement of crop alleles into wild populations due to their specifi c features. For example, backcross seeds produced on wild mothers can persist in the seed bank, illustrating the importance of genetic maternal effects, whereas backcross individuals with either wild or F1 mothers have high fecundity, resulting from their wild-like nuclear genetic composition.

Seed fates in crop–wild hybrid sunflower: crop allele and maternal effects

“…All paternal and maternal parents for seeds generated in 2010 were derived from a previous round of hand pollinations (2009) as described in Alexander et al. (). We generated seeds of 15 sunflower cross types on wild, F 1 crop‐wild hybrid, and crop maternal plants (Table ).…”

“…Removal dates were selected based on a previous seed burial study at this location conducted from 2009 to 2010 (Alexander et al. ; Mercer et al. ).…”

“…; Alexander et al. ). However, such field studies were carried out with a limited number of cross types and thus do not fully represent the genetic diversity likely present at early stages of crop‐wild hybridization.…”

“…; Teo‐Sherrill ; Alexander et al. , ). Third, laboratory research has highlighted variation in seed size and effects of seed coverings on germination behavior for crop, F 1 hybrid, and wild maternal parents (Brunick ; Weiss et al.…”

“…For example, we have learned that cross types precociously germinating in the fall should create a significant source of mortality for some hybrids (Alexander et al. ). Yet we do not understand how the maternal parent of crop‐wild hybrid seed may affect overwinter survival and entry into a persistent seed bank.…”