Variation within Strains of Clover Nodule Bacteria in Size of Nodule Produced and in “Effectivity” of Symbiosis

Biochemical and Symbiotic Properties of the Rhizobia 1

“…This condition was retained for several years although effective forms again appeared upon paing certain of these mutants through the plant. In the light of these results the skepticism with which certain investigators (259,336,362) have viewed previous plant passage experiments (15) seems somewhat paradoxical. The original cultures employed in all aforementioned studies were admittedly not progenies of single cells.…”

“…Virtanen (362) considers ineffectiveness a strain property of greater constancy than effectiveness. Indeed, the loss of effectiveness precedes that of infectiveness among strains altered by prolonged cultivation in unfavorable media (218) and storage in sterilized soil (259,290). After storage of an effective strain for 9 months in sterilized soils, Thornton reports (337, 338) that 30 to 35 per cent of the colonies recovered were ineffective.…”

Plasmids and stability of symbiotic properties of Rhizobium trifolii

“…The use of commercial inocula in the legume industry has long been plagued by an inability of Rhizobium strains tq maintain their symbiotic properties upon introduction to the soil (6,10,11,14). In particular, certain strains were shown to rapidly deteriorate in either their nitrogenfixing capacity or their ability to nodulate the legume host.…”

Symbiotic effectiveness in nodulated red clover

“…of strain and host; uninoculated clover is included as control for bacterial strain. The bacterial strains employed were strains A, CIF and Hannay 7 as effectives, strains Haldon i, SU.297/3 (Baird, iç) and Rothamsted 42 as intermediates, and Rothamsted strains HKC and f12 as ineffectives (the strain f12 is a mutant ineffective derived from strain A and has been found to give a generally similar response to the standard ineffective strain HKC- Nutman, 1946). The results of the experiments are in agreement and show that the ie line responds in an almost completely ineffective manner with all strains of less effectiveness than A.…”