Inefficient nodulation of chickpea (Cicer arietinum L.) in the arid and Saharan climates in Tunisia bySinorhizobium meliloti biovarmedicaginis

Abstract

The aim of this work is to study the genetic diversity and the symbiotic effectiveness of the natural populations of rhizobia nodulating chickpea (Cicer arietinum L.) in six locations of South Tunisia, where chickpea had never been cultivated. Nodules were observed only in the two soil samples from Gafsa (0.8 nodules per plant) and Tataouine (2 nodules per plant). PCR-RFLP typing of 165 rRNA genes of 42 isolates indicated that all analysed strains showed the same ribotype as the reference strainSinorhizobium meliloti RCR2011. These isolates induced ineffective nodules on chickpea andMedicago sativa; however nodules onMedicago laciniata were effective. Analysis of the symbiotic diversity by PCR-RFLP, of thenifDK spacer suggested that all chickpea isolates from the South belong to the biovarmedicaginis ofS. meliloti. The present paper is, to our knowledge, the first report showing that chickpea is selectively nodulated under soil conditions by a specific biovar ofS. meliloti showing specificity toM. laciniata. The specificity of this interaction as well the impact of this inefficient nodulation on chickpea cultivation needs to be investigated further.