Adaptation of rhizobium to subarctic environment in Scandinavia

Summary

Strains of clover rhizobia were isolated from northern Scandinavia (68–70° N.lat.) and, for comparison, also from some places in southern Scandinavia (S. of 63° N.lat.). Pure cultures were used for studies of 1) bacterial growth in liquid culture, 2) nodulation of host plants, and 3) nitrogenase activity, as measured by the acetylene reduction technique, of the host-bacterium association. The tests were performed both at 10°C and 20°C.

In all these respects, the isolates from the subarctic region showed on an average better adaptation to low temperature than the isolates from more southern areas. At 10°C, the former grew faster, nodulated their host plants somewhat earlier and showed a more vigorous acetylene reduction than the latter. At 20°C no significant differences were observed between isolates of different geographical origin.

An adaptation of Rhizobium to a cold climate and a short growing season might be useful for practical purposes, because soil temperatures are usually low at sowing-time in large areas of the temperate zones.