Paired Rhizobia General and Specific Effects on Subterranean Clover Seedling Growth
- M. D. Rumbaugh *,
- K. L. Lawson and
- D. A. Johnson
The relationships among rhizobial strains and their interactions with genetically different legume cultivars should be evaluated before formulating and producing inocula. Diallel analysis procedures were used to compare the performance of one- and two-strain Rhizobium leguminosarum biovar trifolii inocula and to quantify the general and specific interaction effects of the strains on seedling growth of subterranean clover Trifolium subterraneum L. subsp. subterraneum and subsp. brachycalycinum Katzn. and Morley). Ten isolates of rhizobia from the Mediterranean Region were tested as one- and two-strain inocula on three cultivars of subterranean clover grown in tube culture. Two-strain inocula were 2.5% superior to onestrain inocula in increasing clover shoot weight and 2.4% superior in increasing effectiveness of N2 fixation when evaluated for three cultivars. Except for root weight and the number of nodules per plant, the general effects of strains were approximately twice as important as their interaction effects. Rhizobial strain performance was not consistent among the three clover cultivars. Diallel analysis procedures appear to offer promise in quantifying the relationships between legume-Rhizobium combinations and in identifying the most beneficial host-strain combinations for maximizing N2 fixation. A two-stage screening process for inocula development was suggested. Preliminary tests to select strains of high average effectiveness should be followed by diallel performance trials with several cultivars to choose two-strain combinations having high positivespecific interaction effects. One or more two-strain combinations might be used in mixed strain inocula with confidence that they should perform well if sufficiently competitive with indigenous rhizobial populations.
Copyright © 1990 by the Crop Science Society of America, Inc.