Gene Flow in Phaseolus Beans and Its Role as a Plausible Driver of Ecological Fitness and Expansion of Cultigens

Abstract

The genus Phaseolus, native to the Americas, is composed of more than eighty wild species, five of which were domesticated in pre-Columbian times. Since the beginning of domestication events in this genus, ample opportunities for gene flow with wild relatives have existed. The present work reviews the extent of gene flow in the genus Phaseolus in primary and secondary areas of domestication with the aim of illustrating how this evolutionary force may have conditioned ecological fitness and the widespread adoption of cultigens. We focus on the biological bases of gene flow in the genus Phaseolus from a spatial and time perspective, the dynamics of wild-weedy-crop complexes in the common bean and the Lima bean, the two most important domesticated species of the genus, and the usefulness of genomic tools to detect inter and intraspecific introgression events. In this review we discuss the reproductive strategies of several Phaseolus species, the factors that may favor outcrossing rates and evidence suggesting that interspecific gene flow may increase ecological fitness of wild populations. We also show that wild-weedy-crop complexes generate genetic diversity over which farmers are able to select and expand their cultigens outside primary areas of domestication. Ultimately, we argue that more studies are needed on the reproductive biology of the genus Phaseolus since for most species breeding systems are largely unknown. We also argue that there is an urgent need to preserve wild-weedy-crop complexes and characterize the genetic diversity generated by them, in particular the genome-wide effects of introgressions and their value for breeding programs. Recent technological advances in genomics, coupled with agronomic characterizations, may make a large contribution.

Local to continental‐scale variation in fitness and heritability in common bean

“…Selection in common bean has occurred in many regional breeding programs with disparate goals, which commonly develop specific subraces or market classes (Vandermark et al, 2014); this may have enhanced regional adaptation in common bean. Additionally, recent work suggests that continued introgression has helped maintain genetic diversity in common bean, especially between genepool introgression, which may be helpful in maintaining genetic variance and continued yield gains (Chacón-Sánchez et al, 2021;Lobaton et al, 2018). Yet at the same time, several of these bean programs also employ shuttle breeding, which commonly leads to the development of more broadly adapted germplasm (Ortiz et al, 2007).…”

Effects of assisted gene flow on the flowering onset of the annual legumeLupinus angustifoliusL.: from phenotype to genotype

“…Several other studies have shown that gene flow leads to changes in different plant traits. For example, Chacón-Sánchez et al, (2021) reviewed the effects of gene flow between cultivated and wild types of several species of the genus Phaseolus (Leguminosae). Morphological, seed and other traits resulted to be influenced by gene flow events and with important consequences for the species performance.…”

Selection signatures and population dynamics of transposable elements in Lima bean

“…Recent progress in the development of high-throughput sequencing technologies has allowed the genome assembly of a large number of non-model species and significantly increased genomic information in important crops (Marks et al 2021). Recently, Chacón-Sánchez et al (2021) summarized the genomic resources generated in recent years within the Phaseolus genus, showing their importance to evaluate gene flow between gene pools and even between species. Chromosome-level genome assemblies are available for common bean (Schmutz et al, 2014), tepary bean (Phaseolus acutifolius A.…”