Genomic and environmental selection patterns in two distinct lettuce crop–wild hybrid crosses

Abstract

Genomic selection patterns and hybrid performance influence the chance that crop (trans)genes can spread to wild relatives. We measured fitness(-related) traits in two different field environments employing two different crop–wild crosses of lettuce. We performed quantitative trait loci (QTL) analyses and estimated the fitness distribution of early- and late-generation hybrids. We detected consistent results across field sites and crosses for a fitness QTL at linkage group 7, where a selective advantage was conferred by the wild allele. Two fitness QTL were detected on linkage group 5 and 6, which were unique to one of the crop–wild crosses. Average hybrid fitness was lower than the fitness of the wild parent, but several hybrid lineages outperformed the wild parent, especially in a novel habitat for the wild type. In early-generation hybrids, this may partly be due to heterosis effects, whereas in late-generation hybrids transgressive segregation played a major role. The study of genomic selection patterns can identify crop genomic regions under negative selection across multiple environments and cultivar–wild crosses that might be applicable in transgene mitigation strategies. At the same time, results were cultivar-specific, so that a case-by-case environmental risk assessment is still necessary, decreasing its general applicability.

Hybridisation is associated with increased fecundity and size in invasive taxa: meta‐analytic support for the hybridisation‐invasion hypothesis

“…, ; Hartman et al . ); in all cases, differences in λ between taxa reflected differences in survival but not in seed output, suggesting that for Lactuca , survival is a better indicator of λ than is fecundity. Unfortunately, without estimates of λ and individual fitness components from other systems, questions remain about the degree to which these alternative performance metrics may indicate differences in population growth rates.…”

“…; Hartman et al . ). In Raphanus , λ did not differ between paired field populations of resynthesised hybrids and their better performing parental taxon over the second through fourth years post‐hybridisation in Michigan (Campbell et al .…”

“…; Hartman et al . ). Third, the environmental context can determine relative performance of hybrids vs. parents (Arnold & Martin ), and in at least one case, hybrids outperform their parental taxa by way of different traits in different environments (Hovick et al .…”

Intellectual property rights and native traits in plant breeding : a quick scan of patents involving products of conventional plantbreeding

“…regions with QTLs for various types of traits, may be found in particular parts of genomes (e.g. Hartman et al 2013). Thus, it is conceivable that other desirable traits may be identified using a QTL approach in a region where a proprietary trait was already localized.…”

Assessing fitness parameters of hybrids between weed beets and transgenic sugar beets

“…However, in the absence of selective pressure, hybrids can exhibit fitness cost due to the hybridization process and transfer of non‐favourable genes from the crop that consequently inhibit or slow down the introgression phenomenon. Conversely, higher hybrid fitness can occasionally be noted in addition to the new property related to the transgene, for example for radish x wild radish hybrids (Heredia & Ellstrand, ) and lettuce crop x wild backcrossed progeny (Hartman et al., ) as well as increased competitive effects against the crop. Consequently, documenting the relevance of segregating hybrids for resistance is of utmost importance to understand the fate of these hybrids in the presence of selective pressure, and more importantly in the absence of it: most if not all studies dealing with the fitness of herbicide‐resistant variants use herbicide‐free conditions to estimate the cost of resistance (Vila‐Aiub, Neve, & Powles, ).…”