CROSS INOCULATION GROUP SPECIFICITY IN CICER‐RHIZOBIUM SYMBIOSIS

Abstract

SummaryCross‐inoculation group specificity in Cicer arietinum L. (chickpea) was studied. Seventy‐one strains of root nodule bacteria of C. arietinum were examined for nodulation on 87 species of legumes. These species represent all the known cross‐inoculation groups and were selected from various tribes and genera of family Fabaceae and Mimosaceae. In a reciprocal cross‐inoculation study, 287 strains of root nodule bacteria from 52 of the 87 species, were examined on various genotypes of C. arietinum. C. arietinum and its root nodule bacteria did not show cross inoculation affinity with any of the members of the known cross‐inoculation groups: alfalfa, clover, pea, bean, soybean, lupin‐lotus and cowpea miscellany; except for some loose non‐reciprocal kinship with Sesbania, which in its turn has strong affinity with the cowpea miscellany. However, under natural conditions in soil, even the loose non‐reciprocal kinship between Cicer and Sesbania was rare. For practical reasons, it is suggested that C. arietinum and its root nodule bacteria should be considered in a separate cross‐inoculation group.‘Cross‐inoculation host specificity’ appears to be of some help in the revision of the taxonomy of order Leguminosales and supports the placement of Cicer in a monogeneric tribe Cicereae.