Role of fixing nitrogen in common bean growth under water deficit conditions

Abstract

In common bean (Phaseolus vulgaris L), limited information is available if potential of nodulation and symbiotic nitrogen fixation is associated with the expression of traits that confer better adaptation to drought conditions. Adaptive traits were therefore measured in N‐fixing bean lines BAT 477, DOR 364, and PAN 185 and in nonnodulating lines BAT 477‐NN and DOR 364‐NN. Drought affected growth in all bean lines and decreased chlorophyll content but more in DOR 364‐NN and BAT 477‐NN, and also reduced nodule size with highest reduction in DOR 364 (21.6%). Loss of nitrogen fixation under drought conditions was further associated with lower water use efficiency, measured as carbon isotope ratio of 13C/12C, and lower %N in shoots when compared to capability to fix nitrogen. Loss of symbiotic nitrogen fixation in mutant bean lines DOR 364‐NN and BAT 477‐NN negatively affected root architectural traits under drought. Under drought conditions, line BAT 477‐NN had about 50% lower values for all root architectural traits, such as root angle, strongly emphasizing an association of capability to fix nitrogen with root development. An association between capability to fix nitrogen and maintaining a better harvest index and seed yield was also found in the study. Under well‐watered conditions, all N‐fixing lines had a higher harvest index and seed yield (2.6–2.8 t of seed yield/ha) in comparison with the two nonfixing bean lines (1.4 t/ha). Although the harvest index and seed yield declined due to drought in all tested lines, this decline was only significant for line DOR 364‐NN (harvest index) and lines DOR 364‐NN and BAT 477‐NN (seed yield). Our study has overall demonstrated an important association between the capability of maintaining atmospheric N‐fixation and expression of traits conferring better adaptation to drought conditions with any change in nitrogen fixation affecting these traits.

The sweet side of misbalanced nutrients in cadmium‐stressed plants

“…Root development depends on modifications in the patterns of cell multiplication, growth and specialisation (Niu et al, ), which may change root architecture to enhance nutrient and water acquisition given the environmental challenges (Fenta, Beebe, & Kunert, ). Recently, two distinct Mg‐dependent mechanisms for the regulation of root development have been detected in plants under Cd exposure: (a) the enhanced formation of root hairs under an increased Mg concentration, and (b) the delayed development of root hairs under maintained or reduced Mg status in Cd‐treated plants in relation to the control plants (Carvalho et al, ).…”

Root‐omics for drought tolerance in cool‐season grain legumes

“…Genetic variation for nodule numbers has been reported among chickpea varieties under drought conditions, and has been used as an indicator trait for drought tolerance (Labidi et al, 2009). In common bean, drought conditions affect nodule size and nitrogen fixation, leading to poor water use efficiency (Fenta et al, 2020). Moreover, drought conditions changed the root architectural traits in non‐nodulating lines with no symbiotic nitrogen fixation (Fenta et al, 2020).…”

Genome-wide association analysis of bean fly resistance and agro-morphological traits in common bean

“…Common bean ( Phaseolus vulgaris L., 2n = 2x = 22) is one of the most important grain legume crops globally. The crop is cultivated for food, cash income, and improves soil fertility through biological nitrogen fixation [ 1 , 2 ]. It is a primary source of dietary protein for many people in Latin America and sub-Saharan Africa (SSA) [ 3 , 4 ].…”