Allelic Diversity at Abiotic Stress Responsive Genes in Relationship to Ecological Drought Indices for Cultivated Tepary Bean, <i>Phaseolus acutifolius</i> A. Gray, and Its Wild Relatives

• Main Authors: María A. Buitrago-Bitar, Andrés J. Cortés, Felipe López-Hernández, Jorge M. Londoño-Caicedo, Jaime E. Muñoz-Florez, L. Carmenza Muñoz, Matthew Wohlgemuth Blair
• Format: Article
• Language: English
• Published: MDPI AG 2021-04-01
• Series: Genes
• Subjects: abscisic acid-, stress-, and ripening-induced (<i>Asr</i>) gene; candidate gene approach; climate adaptation; dehydration responsive element binding (<i>Dreb</i>) gene; drought tolerance; environmental indices
• Online Access: https://www.mdpi.com/2073-4425/12/4/556

Some of the major impacts of climate change are expected in regions where drought stress is already an issue. Grain legumes are generally drought susceptible. However, tepary bean and its wild relatives within <i>Phaseolus acutifolius</i> or <i>P. parvifolius</i> are from arid areas between Mexico and the United States. Therefore, we hypothesize that these bean accessions have diversity signals indicative of adaptation to drought at key candidate genes such as: <i>Asr2</i>, <i>Dreb2B</i>, and <i>ERECTA</i>. By sequencing alleles of these genes and comparing to estimates of drought tolerance indices from climate data for the collection site of geo-referenced, tepary bean accessions, we determined the genotype x environmental association (GEA) of each gene. Diversity analysis found that cultivated and wild <i>P. acutifolius</i> were intermingled with var. <i>tenuifolius</i> and <i>P. parvifolius</i>, signifying that allele diversity was ample in the wild and cultivated clade over a broad sense (<i>sensu lato</i>) evaluation. Genes <i>Dreb2B</i> and <i>ERECTA</i> harbored signatures of directional selection, represented by six SNPs correlated with the environmental drought indices. This suggests that wild tepary bean is a reservoir of novel alleles at genes for drought tolerance, as expected for a species that originated in arid environments. Our study corroborated that candidate gene approach was effective for marker validation across a broad genetic base of wild tepary accessions.