Early Metabolic and Photosynthetic Responses to Drought Stress in Common and Tepary Bean

Abstract

Common bean (Phaseolus vulgaris L.) is an important food crop, especially in East Africa and Central and South America. Subsistence farmer yields in these areas are limited by the many common bean cultivars that are drought sensitive. Consequently, a major goal of breeding programs is to improve drought tolerance. Our objective was to identify and compare physiological components of drought stress among common bean genotypes varying in stress tolerance. We also included the closely related and highly stress‐tolerant tepary bean (P. acutifolius A. Gray). Compositional parameters often related to drought tolerance revealed no drought effect on free proline, but malate, glucose, fructose, inositol, and raffinose all increased, sometimes enough to osmotically adjust leaf tissues. Abscisic acid (ABA) was especially drought responsive. Although genotypic differences were unrelated to tolerance, grafting revealed that shoot identity controlled ABA levels in stressed roots and that root identity had little or no effect on stomatal behavior. Photosynthetic parameters derived from photosynthesis versus intercellular CO2 concentration curves were not related to drought tolerance, but some traits were related to productivity. Stomatal control and low conductance were clearly associated with tolerance, conserving water during stress, and increasing water use efficiencies. This study should provide guidance in selection of traits associated with enhanced drought tolerance in common bean.

Drought tolerance evaluated in common bean genotypes

“…Thus, reduction in growth in response to the decrease in water availability in the soil can be attributed to a decline in photosynthetic activity through stomatal closing (Chaves;Oliveira, 2004). For Traub, Kelly and Loescher (2017), stomatal conductance is an important parameter for determination of the degree of drought tolerance of a common bean genotype. According to Bragg et al (2004), measurements obtained by the porometer assist in analysis of the physiological status of the plants.…”

“…The expressive mean of stomatal conductance exhibited by the irrigated treatment in relation to water deficit, according to Traub, Kelly and Loescher (2017), occurs because stomatal conductance is closely correlated with soil water status. According to Oliveira, Fernandes and Rodrigues (2005), stomatal conductance can be considered a serious factor that indicates water stress in common bean.…”

Screening for Heat Tolerance in Phaseolus spp. Using Multiple Methods

“…The 10 lines chosen represent a broad range of yield responses to nonstress and drought stress conditions (Table 1, Supplemental Table S3). The five other genotypes were chosen from previous stress experiments (Traub et al, 2017): 'Jaguar' and 'Fuji' are susceptible to drought stress in the field (Kelly et al, 2001(Kelly et al, , 2009b, 'Zorro' is a modern commercial cultivar with moderate drought tolerance (Kelly et al, 2009a), SER 95 is a line that came out of CIAT's drought tolerance breeding program, and TB1 is tepary bean accession that has shown superior drought tolerance in the field (Kumar et al, 1988;Porch et al, 2009). The 15 genotypes were planted sequentially in four time blocks with 1 wk of spacing between each block and two replications of each genotype per block.…”

“…Gray) genotypes or common bean genotypes with tepary in their pedigree were well represented among the heat-tolerant group (Rainey and Griffiths, 2005b;CIAT, 2015). Compared with common bean, tepary bean has a greater tolerance to both heat and drought stress, but the actual resistance mechanisms have been only partially resolved (Castonguay and Markhart, 1992;Udomprasert et al, 1995;Rao et al, 2013;Traub et al, 2017). Compared with common bean, tepary bean has a greater tolerance to both heat and drought stress, but the actual resistance mechanisms have been only partially resolved (Castonguay and Markhart, 1992;Udomprasert et al, 1995;Rao et al, 2013;Traub et al, 2017).…”

“…Tepary bean originated in the Sonoran Desert, located in present-day northwestern Mexico and the southwestern United States and was used as a reliable staple crop in this region for hundreds of years (Nabhan and Felger, 1978). Compared with common bean, tepary bean has a greater tolerance to both heat and drought stress, but the actual resistance mechanisms have been only partially resolved (Castonguay and Markhart, 1992;Udomprasert et al, 1995;Rao et al, 2013;Traub et al, 2017). Tepary bean nonetheless serves as a useful check and ideotype for abiotic stress tolerance in beans (Porch et al, 2009;Beebe et al, 2013).…”