Nature of indigenous rhizobia from Arachis hypogaea L. in some Philippine soils
1990
Gaminde, E.G.C.
The indigenous peanut rhizobia from fields with three different cropping histories had 17 intrinsic antibiotic resistance (IAR) patterns out of 31 possible patterns. Only thru IAR pattern were common to isolate from the three different fields. Seventeen percent of the isolates showed tolerance to acidity in culture. Most of these isolates produced large, gummy, and wet colonies in contrast to the intolerant which formed small, pinpoint, and dry colonies. Seventy-five percent of the acid tolerant isolates were fast growers and twenty-five percent were slow growers. Cropping history did not influence the frequency of acid tolerant isolates. They showed 9 IAR patterns with the fast and slow growers having distinctly different IAR patterns. Serological assay using immuno diffusion (GID) further proved the diversity and unrelatedness of the isolates to the reference strains RP182-13, CB756, P3, and 3G4B20. Symbiotic effectiveness of the isolates was not influenced by cropping history. Tolerance of the native rhizobia to combined nitrogen was shown up to 120 kg N/ha. With sufficient soil moisture rhizobial growth was substantial, but a rapid decline in cell density was noted with the decrease in soil moisture content. The effect of flooding on survival of the isolates varied. Some strains showed tolerance of high moisture level. The selected effective isolates RPG 24, RPG 149, RPG 103, RPG 112, and RPG 211 were as competitive as the reference strains. The selected native peanut rhizobia showed essential and desirable qualities of a competitive inoculum for a successful inoculation program.
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