Adaptation of common bean lines to high temperature conditions: genotypic differences in phenological and agronomic performanceThe International Center for Tropical Agriculture (CIAT) believes that open access contributes to its mission of reducing hunger and poverty, and improving human nutrition in the tropics through research aimed at increasing the eco-efficiency of agriculture.CIAT is committed to creating and sharing knowledge and information openly and globally. We do this through collaborative research as well as through the open sharing of our data, tools, and publications.

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In our study, we analyzed 30years of climatological data revealing the bean production risks for Western Amazonia. Climatological profiling showed high daytime and nighttime temperatures combined with high relative humidity and low vapor pressure deficit. Our understanding of the target environment allows us to select trait combinations for reaching higher yields in Amazonian acid soils. Our research was conducted using 64 bean lines with different genetic backgrounds. In high temperatures, we identified three water use efficiency typologies in beans based on detailed data analysis on gasometric exchange. Profligate water spenders and not water conservative accessions showed leaf cooling, and effective photosynthate partitioning to seeds, and these attributes were found to be related to higher photosynthetic efficiency. Thus, water spenders and not savers were recognized as heat resistant in acid soil conditions in Western Amazonia. Genotypes such as BFS 10, SEN 52, SER 323, different SEFs (SEF 73, SEF 10, SEF 40, SEF 70), SCR 56, SMR 173, and SMN 99 presented less negative effects of heat stress on yield. These genotypes could be suitable as parental lines for improving dry seed production. The improved knowledge on water-use efficiency typologies can be used for bean crop improvement efforts as well as further studies aimed at a better understanding of the intrinsic mechanisms of heat resistance in legumes.

The evaluation of disease resistance is considered an important aspect of phenotyping for crop improvement. Identification of advanced lines of the common bean with disease resistance contributes to improved grain yields. This study aimed to determine the response of the photosynthetic apparatus to natural pathogen infection by using chlorophyll (Chla) fluorescence parameters and their relationship to the agronomic performance of 59 common bean lines and comparing the photosynthetic responses of naturally infected vs. healthy leaves. The study was conducted over two seasons under acid soil and high temperature conditions in the western Amazon region of Colombia. A disease susceptibility index (DSI) was developed and validated using chlorophyll a (Chla) fluorescence as a tool to identify Mesoamerican and Andean lines of common bean (Phaseolus vulgaris L.) that are resistant to pathogens. A negative effect on the functional status of the photosynthetic apparatus was found with the presence of pathogen infection, a situation that allowed the identification of four typologies based on the DSI values ((i) moderately resistant; (ii) moderately susceptible; (iii) susceptible; and (iv) highly susceptible). Moderately resistant lines, five of them from the Mesoamerican gene pool (ALB 350, SMC 200, BFS 10, SER 16, SMN 27) and one from the Andean gene pool (DAB 295), allocated a higher proportion of energy to photochemical processes, which increased the rate of electron transfer resulting in a lower sensitivity to disease stress. This photosynthetic response was associated with lower values of DSI, which translated into an increase in the accumulation of dry matter accumulation in different plant organs (leaves, stem, pods and roots). Thus, DSI values based on chlorophyll fluorescence response to pathogen infection could serve as a phenotyping tool for evaluating advanced common bean lines. Six common bean lines (ALB 350, BFS 10, DAB 295, SER 16, SMC 200 and SMN 27) were identified as less sensitive to disease stress under field conditions in the western Amazon region of Colombia, and these could serve as useful parents for improving the common bean for multiple stress resistance.

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.

Changes in coverage affect the activity of soil's microbial communities, affecting the carbon and nitrogen cycle. The variability of biochemical properties in different coverages (native forest, forest plantation, silvopastoral system and pasture) located in the northwest of the Colombian Amazon was evaluated. Edaphic properties were determined as: organic carbon (OC), total nitrogen (TN), microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) using the fumigation method. A significant effect was found to land use × depth interaction for the variables moisture, pH, CO and MBC/OC ratio (p < 0.05), while MBC and dCO 2 showed differences only for land use and NT, MBN and MBN/TN ratio at depth (p < 0.05). In general, when modifying the soil cover, changes were made in the chemical properties that affected the microbial activity.

Intercropping the common bean (Phaseolus vulgaris L.) with maize (Zea mays L.) is a widely used agronomic practice in smallholder farms in different regions of the world. Although it is a common practice in the Colombian Amazon region, crop yields are low due to the degradation of low fertility, acidic soil and high-temperature stress. Studies are needed on how the integration of genetically adapted common bean breeding lines into an intercropping system can benefit smallholders. The objective of this study was to: (i) evaluate differences in agronomic performance of two common bean lines when intercropped with maize in two different patterns under two types of fertilizer applications; and (ii) identify which intercropping pattern is better to maximize productivity and land use in the Colombian Amazon region. To achieve these aims, 2 field experiments (October 2018 to January 2019, season 1; April to June 2019, season 2) were conducted in the Colombian Amazon region. A randomized complete block design (RCBD) with three replications in a nested trifactorial arrangement in a split-plot scheme was used. The experimental design consisted of 2 advanced bean breeding lines of BFS 10 and ALB 121 (main plots); 3 cropping system patterns, including a monoculture, intercropping pattern 1, and intercropping pattern 2 (subplots); and 2 types of fertilizer, inorganic and organic (sub-subplots), for a total of 12 treatments. The experiment was conducted in two growing seasons in low fertility, acidic soil. Different competition indices and monetary advantage index values were estimated depending on the yield and cost of production from maize and bean intercropping patterns (land equivalent ratio, LER; relative crowding coefficient, RCC; aggressiveness index, AI; competitive ratio, CR). A significant effect on grain yield was observed with both intercropping patterns compared to monocropping of beans and maize. Grain yields obtained for maize were similar under monoculture with both types of fertilizer application, while both bean lines yielded better in monoculture under the application of inorganic fertilizer. Under intercropping patterns, the yield reductions were from 8 to 30% for maize and from 43 to 72% for the 2 bean lines. LER values increased with intercropping patterns under both types of fertilization, which was supported by positive values in the actual yield loss index. The interaction indices between the two crop components showed a greater dominance of maize over beans (RCC, AI, CR). However, the intercropping systems increased the economic advantage (the monetary advantage index) over monocropping. Smallholders in the Amazon region can profit through increased grain yield as well as land-use efficiency by integrating a genetically adapted bean breeding line, BFS 10, as an intercrop with maize under the application of organic fertilizer.

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