Inefficient nodulation of chickpea (Cicer arietinum L.) in the arid and Saharan climates in Tunisia by Sinorhizobium meliloti biovar medicaginis

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 16S rRNA genes of 42 isolates indicated that all analysed strains showed the same ribotype as the reference strain Sinorhizobium meliloti RCR2011. These isolates induced ineffective nodules on chickpea and Medicago sativa; however nodules on Medicago laciniata were effective. Analysis of the symbiotic diversity by PCR-RFLP of the nifDK spacer suggested that all chickpea isolates from the South belong to the biovar medicaginis of S. meliloti. The present paper is, to our knowledge, the first report showing that chickpea is selectively noduiated under soil conditions by a specific biovar of S. meliloti showing specificity to M. laciniata. The specificity of this interaction as well the impact of this inefficient nodulation on chickpea cultivation needs to be investigated further.