| Abstrakt: |
Two field experiments were carried out in Northern Argentina, during the 1989–1990 and 1990–1991 growing seasons, on Argentinian and Brazilian maize genotypes. The inoculant consisted of a mixture of four Azospirillum brasilense strains isolated from surface-sterilized maize roots in Argentina and three A. lipoferum strains isolated from surface-sterilized maize or sorghum roots in Brazil. Establishment of the inoculated strains was confirmed by the antibiotic resistance of the strains in the highest dilution vials. In all treatments, numbers of Azospirillum spp. were increased and the inoculated strains were found in the highest dilutions. While grain yields of the different genotypes varied between 1700 and 7300?kg?ha –1, total N accumulation was much less variable. Significant inoculation effects on total N accumulation and on grain yields were consistently negative with one Argentinian genotype and positive with four Argentinian and two Brazilian genotypes. Significant inoculation effects on leaf nitrate reductase activity at the flowering stage, observed in the range –55% to +176%, indicated the presence of various interactions between the plant NO metabolism and Azospirillumspp. Three Brazilian and one Argentinian maize genotype showed significant decreases in leaf nitrate reductase due to inoculation while four Argentinian genotypes showed significant increases in leaf nitrate reductase activity. The results of the present study, were consistent over the two field experiments and strongly indicate that more detailed plant genotype– Azospirillum spp. strain interaction studies, taking the entire N metabolism in the plant into account, are needed to allow better inoculation results of cereal crops. |
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