A mathematical model for the Rhizobium-legume mutualism

DIANA MARCO; JUAN PABLO CARBAJAL; SERGIO A. CANNAS

Zaragzoa

Congreso; XIII National Meeting of the Spanish Society of Nitrogen Fixation and II Portuguese-Spanish Congress on Nitrogen Fixation; 2010

Spanish Society of Nitrogen Fixation

We analyze the ecology stability of Rhizobium-legume symbiosis, using population dynamic models. We include in the model two rhizobial strains differing in their ability to fix N2 for the plant, and explored the case of sanctions applied by the plant to ineffective rhizobia. Other factors addressed are horizontal transfer of sym genes, competition between fix+ and fix- for nodulation, co-occupation of the same nodule by the two strains, and plant stress. Our model predicts a critical a fraction of fixing rhizobia in soil, represented by the fixing rhizobia needed to provide a minimum N2 amount for plant population persistence. We show that a simple population model can explain the coexistence between fixing and non-fixing strains observed at field, without the need of incorporating any sanction towards non-fixing rhizobia.