Soil fumigation with methyl bromide as a means of increasing the occurrence of the inoculum strain in peanut nodules
1992
Kishinevsky, B.D. | Lobel, R. | Gurfel, D. | Nemas, C.
A field experiment was carried out on sandy loam soil to determine the effect of different pesticides on the nodulation activity of peanut-specific local rhizobia and the recovery rate of the inoculum applied. The experiment included a pesticide-untreated control and the following six treatments: methyl bromide, Edabrom, Edigan (metham-sodium), ethoprophos, fenamiphos and a combination of Edabrom and Edigan. The ELISA (enzyme-linked immunosorbent assay) reactions of nodule antigens (38, 64, 86 and 128 days after planting) showed that despite the pesticides applied, the indigenous peanut Rhizobium population was active in nodulation. However, methyl bromide substantially decreased the number of nodules containing native rhizobial strains. The amount of nodules reacting with antibodies specific to the inoculum strain ranged from 47 to 63%, as compared with 25 to 40% in the control plots and other treatments tested. The positive effect of soil fumigation with methyl bromide on the occurrence of the introduced strain was confirmed in an additional field experiment. Serological evaluation by ELISA showed that 48% of the nodules formed on plants derived from inoculated + methyl bromide-treated plots contained the inoculum strain, as compared with 11% in the inoculated but non-fumigated plots. The highest values of nitrogenase activity and top dry weight were recorded in the inoculated but non-fumigated plots. Although this treatment produced the maximal yield of pods, the differences between inoculated and non-inoculated methyl bromide-treated plots did not reach the threshold of significance. Seed- and pod-weights in the fumigated and inoculated plots were significantly higher than in the other treatments.
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