Distribution pattern of nodules in Phaseolus species and Glycine max

Three distinct patterns of distribution of nodules indicating preferential siting, i.e., localised, diffused and mixed types, could be distinguished in different species of Phaseolus and in Glycine max. These preferential sitings were statistically significant except in the case of P. sublobatus and P. calcaratus I.C. 25. Control experiments in sand cultures also confirmed the above finding. Crosses made between localised (P. aureus N.P. 28) × diffused (P. trilobus) showed dominance of the diffused type over the localised in the F₁. As the F₁ was sterile the segregation of this character could only be studied from backcross progenies of F₁ × P. aureus N.P. 28; this fitted very well with 1:1 ratio indicating that this character is controlled by a single gene difference between the host species.