Selection on Crop-Derived Traits and QTL in Sunflower (Helianthus annuus) Crop-Wild Hybrids under Water Stress

Abstract

Locally relevant conditions, such as water stress in irrigated agricultural regions, should be considered when assessing the risk of crop allele introgression into wild populations following hybridization. Although research in cultivars has suggested that domestication traits may reduce fecundity under water stress as compared to wild-like phenotypes, this has not been investigated in crop-wild hybrids. In this study, we examine phenotypic selection acting on, as well as the genetic architecture of vegetative, reproductive, and physiological characteristics in an experimental population of sunflower crop-wild hybrids grown under wild-like low water conditions. Crop-derived petiole length and head diameter were favored in low and control water environments. The direction of selection differed between environments for leaf size and leaf pressure potential. Interestingly, the additive effect of the crop-derived allele was in the direction favored by selection for approximately half the QTL detected in the low water environment. Selection favoring crop-derived traits and alleles in the low water environment suggests that a subset of these alleles would be likely to spread into wild populations under water stress. Furthermore, differences in selection between environments support the view that risk assessments should be conducted under multiple locally relevant conditions.

Genome‐wide analysis of allele frequency change in sunflower crop–wild hybrid populations evolving under natural conditions

“…Quantitative trait locus (QTL) mapping studies in highly recombined (recombinant inbred line; RIL) sunflower and lettuce crop‐wild hybrids have begun to associate crop‐derived alleles with selectively advantageous phenotypes at a genome‐wide scale (Baack, Sapir, Chapman, Burke, & Rieseberg, ; Dechaine et al., ; Hartman et al., ; Owart, Corbi, Burke, & Dechaine, ), but these studies did not monitor allele frequency change over time. The one study to examine genome‐wide, year‐to‐year evolution of crop alleles under wild conditions found several genomic hotspots and cold areas for crop allele introgression in selfed and backcrossed crop‐wild hybrid lettuce populations (Hooftman et al., ).…”

Contemporary evolution and the dynamics of invasion in crop–wild hybrids with heritable variation for two weedy life–histories

“…For instance, altered germination and survival of crop-wild hybrids were associated with higher relative fitness of hybrid radish in Texas, a newly invaded location (Hovick et al 2012). Similarly, crop-wild hybridization in Helianthus has contributed to adaptive evolution in water stressed environments, by not only selecting for new leaf traits but also larger inflorescence size, a trait likely to change the demography of weedy sunflower population (Owart et al 2014). Thus, rates of adaptive evolution that result in crop allele introgression depend on the rate of gene flow, the mode of inheritance of traits, and the relative fitness of heritable crop versus wild phenotypes in a weed population (Nuismer et al 2012).…”

“…; Owart et al. ). Indeed, over short‐time scales, crop‐to‐wild gene flow can be a more significant source of adaptive genetic variation than mutation (Gomulkiewicz et al.…”

“…The impact of crop-wild gene flow depends on rates of gene flow and the relative success of heritable, migrant phenotypes when compared with the recipient population's adaptive optima (Snow et al 2003;Hooftman et al 2005;Mercer et al 2006). Studies on crop-wild hybrid populations show that the successful phenotypes are not always a random subset of genotypes from parental populations (Ellstrand and Schierenbeck 2000;Hovick and Whitney 2014), and hybrid populations may facilitate the transfer of novel, adaptive traits to recipient weed populations (e.g., Snow et al 2003;Hooftman et al 2011;Owart et al 2014). Indeed, over short-time scales, crop-to-wild gene flow can be a more significant source of adaptive genetic variation than mutation (Gomulkiewicz et al 1999;Holt et al 2004).…”

Assessing the effects of hybridization and precipitation on invasive weed demography using strength of selection on vital rates

“…In drought conditions, water loss is highly detrimental to fitness, so drought tolerance should be strongly favoured [24]. As well, crop plants are thought to have better drought tolerance than their wild relatives [25, 26], so altered precipitation patterns by human-mediated global climate change may have a substantial effect on selection between wild and hybrid weeds [27, 28]. In agricultural plant communities, where crop and compatible weedy relatives coexist, we may expect different life-history responses to identical environmental cues [29].…”