Abstract
The common bean is susceptible to drought conditions and the evaluation of plant responses to low water availability can be difficult. The quantification of chlorophyll fluorescence as a sensitive trait to environmental stresses is an important alternative in the characterization of drought-susceptible genotypes. The objective of this study was to evaluate mainly the use of chlorophyll α fluorescence (maximum efficiency of PSII (Fv/Fm), photochemical quenching (qP), non-photochemical quenching (NPQ)) and rapid light-response curves (RLCs) (initial slope of the curve (α), minimum saturation irradiance (Ik) and maximum relative electron transport rate (ETRmax)) parameters as tools for the identification of susceptible or tolerant bush bean cultivars to water deficit stress conditions in two different phenological stages. Using a randomized block design in a factorial arrangement, five bush bean cultivars (Cerinza, Bachue, NUA35, Bacata and Bianca) were evaluated under water deficit conditions by the suspension of irrigation for 15 days from 40 to 55 Days after Emergence (DAE) (vegetative stage) or 50 to 65 DAE (reproductive stage). The results showed that Fv/Fm and NPQ recorded the highest variation due to water deficit conditions, especially in the vegetative stage. The greatest reductions in Fv/Fm (0.67) and NPQ (0.71) were evidenced in cultivar NUA35 compared to its control plants (0.78 and 1.07, respectively). The parameters obtained from RLCs showed that cultivar Bacata registered the lowest α (0.17) and Ik (838.19 μmol∙m−2∙s−1) values compared to its control plants (α 0.23; Ik 769.99 μmol∙m−2∙s−1). Differences were only obtained in ETRmax in the reproductive stage (50–65 DAE) in which cultivar NUA35 reached values of 158.5 in stressed plants compared to control plants (251.22). In conclusion, the parameters derived from RLCs such as α and Ik can be used as tools to identify drought susceptibility in the vegetative stage, whereas ETRmax can be used in the reproductive stage. In addition, PSII photochemistry (Fv/Fm and NPQ) can also help to understand the agronomic responses of common bush bean cultivars to drought conditions.
Highlights
The common bean (Phaseolus vulgaris L.) is the most cultivated and consumed grain legume in the world and plays an important role in the human diet due to its high protein and mineral content [1,2].A worldwide production of 55,627 Mt in 38,038,865 ha was recorded for green and dry beans in 2017 [3].Studies have projected a reduction in climate conditions due to heat and drought stress in a large part of bean crops in South America [4].Plants are naturally exposed to different abiotic and biotic stress conditions [5]
PSII photochemistry (Fv /Fm and non-photochemical quenching (NPQ)) can help to understand the agronomic responses of common bush bean cultivars to drought conditions
It is important to point out that there was a greater reduction of the total chlorophyll content in cultivar Bacata plants that were subjected to water deficit stress conditions during the vegetative stage (1517.65 μg mg−1 Fresh Weight (FW))
Summary
The common bean (Phaseolus vulgaris L.) is the most cultivated and consumed grain legume in the world and plays an important role in the human diet due to its high protein and mineral content [1,2].A worldwide production of 55,627 Mt in 38,038,865 ha was recorded for green and dry beans in 2017 [3].Studies have projected a reduction in climate conditions due to heat and drought stress in a large part of bean crops in South America [4].Plants are naturally exposed to different abiotic and biotic stress conditions [5]. A worldwide production of 55,627 Mt in 38,038,865 ha was recorded for green and dry beans in 2017 [3]. Studies have projected a reduction in climate conditions due to heat and drought stress in a large part of bean crops in South America [4]. Plants are naturally exposed to different abiotic and biotic stress conditions [5]. Drought is the most decisive abiotic stress for crop yield and productivity, demanding a continuous knowledge of plant responses to this condition [6,7]. Plants under water deficit stress show a wide range of responses that include morphological, physiological, biochemical and molecular changes [8].
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