A Time Course Study and Competition between Rhizobia-Affecting Nodulation in Two Soybean Genotypes

greenhouse experiment was conducted to evaluate the time
course of nodulation and completion between strains USDA 123
and CB 1809 on Williams soybean and on P1 377578 (#671). This P1
has been shown to restrict nodulation and competition of USDA 123.
The study was performed using vermiculite and fine sandy loam soil
as growth media. Nodulation and competition in both medium were
evaluated at 4, 6, 8 and 10 weeks. Three additional treatments
included delayed inoculation of CB 1809 at 1, 2 and 4 weeks after
inoculation the soil with USDA 123 were also performed. Averaged
over the dates, strain USDA 123 produced 35 and 37%, respectively
of the nodule mass and number on P1 377578 as compared to
CB1809. In competition for nodulation in vermiculite, USDA 123
formed 43, 80, 62 and 64% of the nodules on Williams at 4, 6, 8 and
10 weeks, respectively, while only formed 0, 16, 9 and 16 % of the
nodule on P1 # 671. In soil, USDA 123 formed 95% or more of the
nodule on Williams through 10 weeks, while it formed 29% or less of
the nodules on P1 # 671. In the delayed inoculation treatments a
maximum of 14% of the nodules on Williams were formed by CB
1809, whereas on P1 # 671 a ratio of 89% or more were colonized by
the same strain. The marked influence of the host on competition and
affinity to nodulate with certain strain is demonstrated in this study.