Drought stress and high heat tolerance in domesticated Phaseolus beans

Abiotic constraints, such as drought and heat driven by climate change,
negatively impact the production of the common bean (Phaseolus vulgaris
L.), an essential grain legume worldwide. The ability to tolerate drought
and heat stress in common bean can be improved by introducing genetic
variation from related species, such as tepary bean (Phaseolus acutifolius
A. Gray), which has recently gained attention because of its adaptation to
drought and heat stresses and potential use as a genetic resource and
alternative crop. To better understand the phenotypic response of tepary
bean to drought and heat stress in multiple environments and trials and to
select highly adapted tepary beans, we conducted two field experiments. In
Experiment 1, we compared the adaptation to drought stress of tepary bean
(n = 10), common bean (n = 10), and Lima bean (Phaseolus lunatus L.; n =
9) by assessing the reduction in grain yield under terminal drought
compared to well-irrigated conditions in two California locations with
arid summer conditions. Of the three species, tepary bean showed the
statistically strongest adaptation to terminal drought, followed by Lima
bean and common bean. In Experiment 2, we evaluated a set of 22 tepary
beans from contrasting origins for drought and heat stresses across
multi-environment trials (METs), in California, Nebraska, and Colombia,
with common bean as a control. We found a considerable variation in the
tepary bean phenotypic response to these MET conditions, as a result of a
strong genotype x environment (G x E) interaction. Also, we identified
tepary bean accessions adapted to drought, heat, and well-irrigated
conditions across multiple climate zones. Understanding the performance of
tepary bean across multiple environments and identifying tepary beans with
broad and target-specific adaptation will maximize the potential use of
the species.