Physiological Characteristics of Cultivated Tepary Bean (Phaseolus acutifolius A. Gray) and Its Wild Relatives Grown at High Temperature and Acid Soil Stress Conditions in the Amazon Region of Colombia

Abstract

Common bean (Phaseolus vulgaris L.) is sensitive to different types of abiotic stresses (drought, high temperature, low soil fertility, and acid soil), and this may limit its adaptation and consequently to its yield under stress. Because of this, a sister species, tepary bean (Phaseolus acutifolius A. Gray), has recently gained attention in breeding for improved abiotic stress tolerance in common bean. In this study, we evaluated the adaptation of 302 accessions of tepary bean (Phaseolus acutifolius A. Gray) and its wild relatives (grouped in four types of tepary bean genetic resource: cultivated, acutifolius regressive, acutifolius wild, tenuifolius wild) when grown under high temperature and acid soil conditions with aluminum toxicity in the Amazon region of Colombia. Our objective was to determine differences among four types of tepary bean genetic resource in their morpho-phenological, agronomic, and physiological responses to combined high temperature and acid soil stress conditions. We found that cultivated P. acutifolius var acutifolius presented a greater number of pods per plant, as well as larger seeds and a greater number of seeds per pod. Some traits, such as root biomass, days to flowering and physiological maturity, specific leaf area, and stomatal density, showed significant differences between types of tepary bean genetic resource, probably contributing to difference in adaptation to combined stress conditions of high temperature and acid soil conditions. The photochemical quenching (qP) was higher in cultivated P. acutifolius var. acutifolius, while energy dissipation by non-photochemical quenching (NPQ) in the form of heat and the coefficient of non-photochemical dissipation (qN) were higher in acutifolius regressive and tenuifolius wild accessions. We have identified 6 accessions of cultivated and 19 accessions of tenuifolius wild that exhibited grain yields above 1800 kg ha^-1. These accessions could be suitable to use as parents to improve dry seed production of tepary bean under combined stress conditions of high temperature and acid soil.

Keywords: agronomic characteristics; chlorophyll fluorescence; energy use; heat tolerance; yield.

Figure 1

Box plots of the scatter plot for agronomic characteristics at the plant (a–d), pod (a,e,f), and seed (g,h) levels among the tepary bean genetic resource. Dotted line means the overall mean for each variable. Different letters between tepary bean genetic resource indicate different means (p < 0.05).

Figure 2

Box plots of the scatter plot for agronomic grain characteristics in terms of viable and non-viable seeds per plant (a–d), viable and non-viable seeds per pod (e,f), 100 seeds weight (g) and grain yield (h) of tepary bean genetic resource. Dotted line means the overall mean for each variable. Different letters between tepary bean genetic resource indicate different means (p < 0.05).

Figure 3

Box plots of the scatter plot for morphological (a–d), phenological (days to flowering (e) and days to physiological maturity (f)) and physiological (g,h) characteristics of tepary bean genetic resource. Dotted line means the overall mean for each variable. Different letters between tepary bean genetic resource indicate different means (p < 0.05).

Figure 4

Images of chlorophyll a fluorescence parameters taken in fully developed leaves at the onset of physiological maturity the tepary bean genetic resource: (a) Initial fluorescence (F₀), (b) maximum fluorescence (F_m), (c,d) maximum quantum efficiency of PSII (F_v/F_m). (d) An example of the area of interest (AOI) tested on each leaf to obtain the fluorescence variables is shown. Gradient in color change from violet to red means higher to lower value for each variable.

Figure 5

Behavior of the photosynthetic machinery as a function of PAR among the tepary bean genetic resource. (a) Photochemical yield (Y(II)), (b) electron transport rate (ETR). In the upper panel, gradient in color change from violet to red means higher to lower value for each variable. Means and error bars correspond to 20 AOI (area of interest) from four leaves of each accession, i.e., 5 AOI were tested on each leaf.

Figure 6

Different energy pathways as a function of PAR among the tepary bean genetic resource. (a) Photochemical quenching (qP), (b) non-photochemical quenching (NPQ), (c) coefficient of non-photochemical dissipation (qN). In the upper panel, gradient in color change from violet to red means higher to lower value for each variable. Means and error bars correspond to 20 AOI (area of interest) from four leaves of each accession, i.e., 5 AOI were tested on each leaf.

Figure 7

Chord diagram of correlation coefficients between agronomic, phenological and physiological variables the tepary bean genetic resource. Ribbons inside the circle correspond to significant correlations with a p-value < 0.05; blue ribbons indicate positive coefficients and red ribbons indicate negative coefficients. Width of pods (WP), length of pods (LP), pods mass (Podg), viability of pods (ViaP), seeds per pod (SepP), weight (g) of 100 seeds (SW), viability of seeds in the pod (ViaP), pollen viability (PV), grain yield (GY), photochemical pathway (qP), fraction dissipated as heat (NPQ), relative chlorophyll (RC), maximum fluorescence level (F_m), photochemical yield (Y(II)), and electron transport rate (ETR).

Figure 8

Distribution of rainfall and maximum/minimum temperatures during the crop growing period at the Macagual Research Center in Colombia in two seasons: October 2019–January 2020 (left); and October–January 2021 (right).