Persistence of sunflower crop traits and fitness in Helianthus petiolaris populations

Abstract

Transgenic plants have increased interest in the study of crop gene introgression in wild populations. Genes (or transgenes) conferring adaptive advantages persist in introgressed populations, enhancing competitiveness of wild or weedy plants. This represents an ecological risk that could increase problems of weed control. Introgression of cultivar alleles into wild plant populations via crop-wild hybridisations is primarily governed by their fitness effect. To evaluate this, we studied the second generation of seven wild-crop interspecific hybrids between weedy Helianthus petiolaris and cultivated sunflower, H. annuus var. macrocarpus. The second generation comprised open-pollinated progeny and backcrosses to the wild parent, mimicking crosses that occur in natural situations. We compared a number of morphological, life history and fitness traits. Multivariate analysis showed that the parental species H. annuus and H. petiolaris differed in a number of morphological traits, while the second hybrid generation between them was intermediate. Sunflower crop introgression lowered fitness of interspecific hybrids, but fitness parameters tended to recover in the following generation. Relative frequency of wild/weedy and introgressed plants was estimated through four generations, based on male and female parent fitness. In spite of several negative selection coefficients observed in the second generation, introgressed plants could be detected in stands of <100 weedy H. petiolaris populations. The rapid recovery of fecundity parameters leads to prediction that any trait conferring an ecological advantage will diffuse into the wild or weedy population, even if F1 hybrids have low fitness.

Crop‐to‐wild gene flow and its fitness consequences for a wild fruit tree: Towards a comprehensive conservation strategy of the wild apple in Europe

“…Hybridization from cultivated to wild populations can threaten the persistence of wild taxa, through either (i) demographic swamping, in which hybrids with reduced fitness decrease population growth rates, or (ii) genetic swamping, in which hybrids with moderate‐to‐high fitness replace pure wild genotypes over time (Todesco et al., ; Wolf, Takebayashi, & Rieseberg, ). It has long been assumed that crop–wild hybrids would have a lower fitness than their wild parent in natural habitats as has been shown, for instance, in sunflowers (Gutierrez, Cantamutto, & Poverene, ). However, in many other cases, hybrids showed no decrease in fitness, for instance in Sorghum (Arriola & Ellstrand, ).…”

Effect of a Geographic Barrier on Adaptation in the Dwarf Sunflower (Helianthus pumilusNutt.)

“…Fecundity is commonly used to measure fitness in Helianthus (Burke and Rieseberg 2003;Mercer et al 2006;Whitney et al 2006;Gutierrez et al 2011). However, fecundity may only rarely be the best predictor of population growth rates (Crone 2001).…”

Gene Flow from Herbicide-Resistant Crops to Wild Relatives

“…It long dominated the view that crop-wild hybrids have a lower fitness than their wild parent [75,76]. But, many studies confirmed that some hybrids display increased [47], while the other display reduced [77] fitness in comparison with their parents. Displayed fitness depends not only on the crop traits introduced to wild relatives, but also on environmental conditions.…”