Effects of assisted gene flow on the flowering onset of the annual legume Lupinus angustifolius L.: from phenotype to genotype.

Abstract

Current climate change may impede species to evolutionary adapt quickly enough to environmental changes, threatening their survival. In keystone populations, it may be necessary to consider the introduction of adaptive alleles through assisted gene flow. Considering that flowering time is a crucial trait in plant response to global warming, the objective of our study was to test the potential benefits and limitations of assisted gene flow for enhancing the evolutionary potential of Lupinus angustifolius L. (Fabaceae) populations through the advancement of flowering time in the context of global warming. Previous studies have shown that southern populations of L. angustifolius flower earlier than northern populations. We collected seeds from four populations in Spain from two different latitudes, and we established them in a common garden environment. To advance the flowering onset of northern populations, we used pollen from southern individuals to pollinate plants from northern populations, creating an F1 gene flow line. In the following season, the F1 gene flow line was self-pollinated to create an F2 self-pollination line. In parallel, individuals from the F1 gene flow line were pollinated again with pollen from northern plants, thus creating a backcross line. We also included a control line resulting from a random selection of individuals in each population in the first generation and their descendants from self-crosses in the second generation. We measured flowering onset, reproductive success and other plant traits in all individuals resulting from these lines. To characterize the effects of the assisted gene flow line at the genomic level, we carried out a gene capture analysis to sequence genes related to reproduction, growth, stress, nitrogen, and alkaloids in individuals from the F1 gene flow line and the control line in the first generation. All gene flow-derived lines flowered significantly earlier than the control line. Furthermore, plants from the F1 gene flow line produced heavier seeds and had a lower shoot growth than the control line. Genomic analyses identified 36 SNPs outliers that were associated to flowering onset, seed weight, and shoot growth. These results highlight that assisted gene flow can increase the evolutionary potential of populations by modifying the values of a specific trait. However, the modification of one trait may affect the values of other plant traits. The characteristics of the populations will have a fundamental effect on the results of assisted gene flow. Therefore, the selection of the donor population is a critical step in this process.