EFFECTS OF RHIZOBIOPHAGES AND FUNGICIDES ON GROWTH OF BRADYRHIZOBIUM JAPONICUM AND RH1ZO- BIUM MELILOTI AS WELL AS NODULATION AND GROWTH OF SOYBEAN AND ALFALFA

SHAHABY, AHMED F.; EMAM, NADIA F.; HASSAN, MOHAMED E.; EL-SAWI, MAGDY M.; ZAHRA, MOAWAD K.

doi:10.21608/ejar.1999.326145

EFFECTS OF RHIZOBIOPHAGES AND FUNGICIDES ON GROWTH OF BRADYRHIZOBIUM JAPONICUM AND RH1ZO- BIUM MELILOTI AS WELL AS NODULATION AND GROWTH OF SOYBEAN AND ALFALFA

Document Type : Original Article

Authors

¹ Department of Microbiology, Faculty of Agriculture, Cairo University, Giza, Egypt

² Agricultural Microbiology Research Department, Soils, Water and Environment Institute, Agricultural Research Center, Giza, Egypt

10.21608/ejar.1999.326145

Abstract

The effects of rhizobiophages and fungicides (Rizolex and Ben-late) on Bradyrhizobiurn japonicum and Rhizobium meliloti as well as nodulation, N7-fixation and growth of soybean and alfalfa were investigated. Both phage-and fungicide resistant rhizobia and bradyrhizobia mutants were secured. Rhizobium and Bradyrhizobium strains showed variable sensitivity to phages. Rhizobiophages effective on rhizobia strains produced clear, round and variable size of plaques. strains and their phageresistant isolates exhibited marked variations in their responses to different concentration of the tested fungicides depending on the strain and the type of fungicide used and its level of application. Rizolex at 75 ppm concentration decreased the growth of rhizobial strains and their phage-resistant isolates. No growth was obseved for all tested strains when the lethal level (125 ppm) of Rizolex was used. All rhizobial strains and their phage-resistant isolates showed good growth at 700 and 800 ppm of Benlate, but 900 ppm reduced the growth of all tested strains. Benlate at 1200 ppm concentration was lethal for all strains. Inoculation of both legumes with their specific rhizobia promoted nodulation, growth and increased nitrogen content of plants. Increases in plant parameters depended on the type of inoculant with or without phage, Rhizolex or both. The highest nodulation, growth and nitrogen content were recorded when parent strains were applied without any additives compared to their phage-resistant isolates (PRI), Rizolex-resistant isolates (RRI) and phage-Rizolex-resistant isolates (PRRI). Addition of phage, Rhizolex or both to the parent strains or their resistant isolates caused more decreases in all plant parameters. Inoculated plants receiving fungicides recorded the least values of nodulation, plant biomass and nitrogen content. The numbers of R. Meliloti TAL380 and B. Japonicum USDA 218 sharply decreased after 50 and 45 days of planting, respectively; and more decreases were recorded at the second period of analysis, 90 and 75 days, in the same order. Marked reductions in rhizobia populations were recorded when phage was added to its homologous rhizobia. The phage particles in the inoculated treatments increased at 45-and 50-day periods compared to the initial levels then sharply decreased with progressive growth. Numbers of phages were particularly high in treatments received phages.