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Limitations of the enzyme‐linked immunosorbent assay for routine determination of legume inoculant quality
Author(s) -
Lochner H.H.,
Strijdom B.W.,
Kishinevsky B.,
Steyn P.L.
Publication year - 1988
Publication title -
journal of applied bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 0021-8847
DOI - 10.1111/j.1365-2672.1988.tb03377.x
Subject(s) - microbial inoculant , legume , inoculation , rhizobium , bradyrhizobium , horticulture , seedling , biology , chemistry , agronomy
Peat inoculants containing strains of either Rhizobium or Bradyrhizobium spp. were used to determine correlations between cell numbers and A 405 values obtained with double antibody sandwich enzyme‐linked immunosorbent assay (DAS ELISA) and indirect ELISA. ELISA values of inoculants containing strains of Rhizobium were weak and non‐specific; with Bradyrhizobium spp. strains, readings were higher and cross‐reactions negligible when heated inoculant suspensions were allowed to stand for 3 h before ELISA determinations were made. With soybean inoculant, correlation coefficients of r = 0.93 and 0.83 were obtained with DAS and indirect ELISA, respectively. A linear curve relating log cell numbers to A 405 values was used to determine the reliability of DAS ELISA values obtained over 2 years with tests on commercially produced soybean inoculants. In the range 5 times 10 8 ‐ca 3 times 10 9 cells/g inoculant, DAS ELISA estimates closely followed plate counts but no significant correlation was found when inoculants contained >ca 3 times 10 9 cells/g. With a minimum requirement of 1 times 10 9 cells/g inoculant, discrepancies between DAS ELISA estimates and plate counts obtained with inoculants produced with gamma‐irradiated peat would have resulted in the erroneous rejection or acceptance of 14.5% of all inoculants tested, based on DAS ELISA estimates. With inoculants produced with steam‐sterilized peat, which was unfavourable for survival of strain WB1, 70.0% of the inoculants rejected because of low plate counts would have been acceptable on the basis of DAS ELISA estimates.