Search

International audience; Low phosphorus (P) availability is a primary factor that limits the production of common bean (Phaseolus vulgaris L.) in many parts of the world, especially when plant growth depends on N2 fixation. In order to understand how common bean copes with this nutritional constraint, two recombinant inbred lines (RILs) of common bean namely RILs 115 and 147 were studied in the field conditions during three growing seasons from 2012 to 2014. At flowering stage, plants were harvested and analyzed for their nodulation, growth, P content and yield. Results showed that for RIL115, the nodulation (43%), shoot (28%) and root growth (32%) was higher than for RIL147 in a low-P availability soil whatever the growing season. In addition, RIL115 had better growth and efficiency in use of P for the rhizobial symbiosis (7.29 mg nodule dry weight mg−1 nodule P) about twice higher may be involved in tolerance to low-P, and to be a useful marker for field data. At harvest, the RIL115 showed higher grain yield (1146 kg ha−1) than the RIL147 (1045 kg ha−1). It is concluded that the genotype of RIL 115 had a higher yield and could best adapt to low-P availability under field condition.

International audience; While increased P-hydrolysing acid phosphatases (APase) activity in bean nodules is well documented under phosphorus (P) limitation, gene expression and subcellular localization patterns within the N2-fixing nodule tissues are poorly understood. The aim of this research was to track the enzyme activity along with the intra-nodular localization of fructose-1,6-bisphosphatase (FBPase), and its contribution to P use efficiency (PUE) under symbiotic nitrogen fixation (SNF) in Phaseolus vulgaris. The FBPase transcript were localized in situ using RT-PCR and the protein activity was measured in nodules of two contrasting recombinant inbred lines (RILs) of P. vulgaris, namely RILs 115 (P-efficient) and 147 (P-inefficient), that were grown under sufficient versus deficient P supply. Under P-deficiency, higher FBPase transcript fluorescence was found in the inner cortex as compared to the infected zone of RIL115. In addition, both the specific FBPase and total APase enzyme activities significantly increased in both RILs, but to a more significant extent in RIL115 as compared to RIL147. Furthermore, the increased FBPase activity in nodules of RIL115 positively correlated with higher use efficiency of both the rhizobial symbiosis (23%) and P for SNF (14% calculated as the ratio of N2 fixed per nodule total P content). It is concluded that the abundant tissue-specific localized FBPase transcript along with induced enzymatic activity provides evidence of a specific tolerance mechanism where N2-fixing nodules overexpress under P-deficiency conditions. Such a mechanism would maximise the intra-nodular inorganic P fraction necessary to compensate for large amount of P needed during the SNF process.