Anatomical comparison of wild-type and non-nodulating mutant chickpea (Cicer arietinum)

Abstract

Non-nodulating chickpea (Cicer arietinum L.) mutant PM233B was characterized anatomically via comparison with its normally nodulating parent line ICC 640. Root hair and cortical cell infection threads, cortical cell division centers, and nodule formation were observed by light microscopy in serial root sections of ICC 640, but were absent in PM233B. Scanning electron microscope observations of inoculated root sections showed that ICC 640 and PM233B were indistinguishable in adsorption of chickpea Rhizobium strain CC1192. Thus, the rhizobial infection process was blocked in PM233B at a stage subsequent to root hair adsorption of bacteria, but prior to initiation of infection threads and root cortical cell division. Reciprocal shoot grafts between ICC 640 and PM233B demonstrated that the non-nodulation phenotype of PM233B was controlled by the root, and not the shoot, genotype. Key words: chickpea, Cicer arietinum, root nodule, symbiosis, non-nodulating mutant.