Analysis of host genotype x rhizobial strain interaction in N2 fixation

Summary A method of analyzing host genotype x rhizobial strain interaction for N₂ fixation potential, based on the principle of structural relationship analysis, is proposed. When this interaction is significant, selecting genotypes for high N₂ fixation potential is incorrect, because the N₂ fixation efficiency is dependent on the rhizobial strain used. Under such circumstances, grouping genotypes based on average fixing ability (AFA), a linear response to the effectiveness of rhizobial strain, and specific fixing ability (SFA), deviation from the linear response in terms of the magnitude of the error variance, is useful before initiating a breeding program for enhanced N₂ fixation. Host genotype x strain interaction effect is partitioned into two components, and two parameters are derived which estimate AFA and SFA. N₂ fixation data from 3 mungbean genotypes and 6 rhizobial strains are used to illustrate this method.