IN INOCULANTS Nodulaid - 17th International Nitrogen Fixation ...

17 th International Congress on Nitrogen Fixation
Fremantle, Western Australia
27 November – 1 December 2011
Session Details: Thursday 1 December 2011
Concurrent Session 18 – P Nutrition & Symbioses
1100 – 1230
Authors: Bargaz Adnane 1,2 , Faghire Mustapha 1 , Mandri Btissam 1 , Farissi Mohamed 1 , Jean
Jacques Drevon 2 , and Ghoulam Cherki 1
1 Equipe de Biotechnologie Végétale et Agrophysiologie des Symbioses, Faculté des
Sciences et Techniques Guéliz-Marrakech, BP 549, 40000, Marrakech, Morocco.
2 INRA-IRD-SupAgro, UMR Eco&Sols - Ecologie Fonctionnelle & Biogéochimie des Sols
& Agroécosystèmes 2 Place Viala, F34060, Montpellier, France.
Presentation Title: Phosphorus deficiency affected conductance to O2 and ascorbate peroxydase gene
expression in nodules of Phaseolus vulgaris-rhizobia symbiosis
Presentation Time: 1200 – 1220
Although recent studies have addressed the effects of phosphorus (P) deficiency on nodule respiration and
oxidative stress, little attention has been given to elucidate the relationships between nodule permeability, nodule
P status, and antioxidative responses. To study these traits, two recombinant inbred lines, namely RILs L115 and
L147 were inoculated with Rhizobium tropici CIAT899, and grown in hydroaeroponic culture under P-sufficiency
(250) versus P-deficiency (75 µmol P plant -1 week -1 ) conditions. At the flowering stage, plants and nodules
biomasses, P contents and localization of nodule ascorbate peroxidase (APX) transcripts were determined after
measuring O2 uptake by nodulated roots and nodule conductance to O2 diffusion (gn). The results showed that Pdeficiency
significantly decreased plant growth and nodulation, with differences between bean genotypes. Pdeficiency
also induced a decrease in nodule P content (31%) in the sensitive L147 and tolerant line L115, a 42
and 27% reduction in shoots of sensitive and tolerant lines, respectively. Under P-deficiency, gn increased more
for the sensitive (39%) than for the tolerant lines (27%). This increase was linked to a rise both in the P levels in
nodules and shoots, as well as in the efficiency of symbiotic nitrogen fixation as determined by nodule-dependent
biomass production for the sensitive lines. Furthermore, positive correlations were found between O2
permeability, gn and P content both in nodules and shoots (r 2 = 0.94** and r 2 = 0.96**). Additionally, P-deficiency
increased electrolyte leakage, the oxidative stress and the transcripts for ascorbate peroxidase gene in nodules.
The later was more abundant in the inner cortex and the infected cells close to inner cortex. We conclude that gn
increased with increases in both nodule P content and antioxidative responses.
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