Abstract
The effect of different nitrogen sources (glucosamine sulfate, ammonium sulfate, aspartic acid, phenylalanine and peptone) in comparison to sodium nitrate, the major nitrogen compound in basal agar Czapek’s synthetic medium growth were studied on the linear growth of Rhizoctonia solani and its pathogenicity on faba bean germinated seeds. Ammonium sulfate exhibited faster liner growth and showed the same effect as the basal medium with sodium nitrate while glucosamine sulfate showed less growth rate compared with sodium nitrate. Glucosamine sulfate and ammonium sulfate showed a significant reduction in number of infection cushions which led to significant decrease of disease index in vitro. Under greenhouse conditions, glucosamine sulfate or peptone as a sole nitrogen sources in food requirements of Rhizoctonia solani inoculum depressed the virulence of the fungus. The effect of different amounts of glucosamine sulfate was determined on fungal growth rate, infection cushions, disease index in vitro and polyphenol oxidase activity. Increasing amount of glucosamine sulfate showed significant reduction of growth rate in comparison to the basal medium with sodium nitrate. All seeds subjected to R. solani grown on different amount of glucosamine sulfate showed the lower number of infection cushions, disease index and polyphenol oxidase activity compared with sodium nitrate. Under greenhouse conditions, disease index showed a significantly decreased effect when glucosamine sulfate used as soil applications and showed better effect on shoot weight and root weight compared with control plants treated with sodium nitrate. Our study proposes that glucosamine sulfate may act as controlling factor of pathogenicity genes of R. solani
Highlights
Nitrogen is an essential element for the growth of all living organisms including fungi and soil microorganisms
Since cultivated soil usually fertilized by different N sources includes nitrate, ammonium salts or organic amendments, the fungal inoculum will feed either of these fertilizers which may affect its pathogenicity
The first one is studying the effect of nitrogen sources included mineral i.e. sodium nitrate, ammonium sulfate or simple organic i.e. glucosamine sulfate, phenylalanine, aspartic acid and protein i.e. peptone on fungal growth and its pathogenicity on faba bean seeds
Summary
Nitrogen is an essential element for the growth of all living organisms including fungi and soil microorganisms. Effect of different amount of glucosamine sulfate on disease index and plant growth characters under greenhouse conditions Preparation of inoculum and infestation of sandy pots: Sand washed with hydrochloric acid and sterilized in the autoclave was placed in 9 cm Petri dishes (120 g sand/plate). RESULTS Five nitrogen sources: glucosamine sulfate, ammonium sulfate, aspartic acid, phenylalanine and peptone were replaced with the equivalent of nitrogen units in the basal agar Czapeks synthetic medium as the sole nitrogen source to determine their effect on growth rate and pathogenicity of Rhizoctonia solani as well as the basal constituent of Czapex’s medium. The effect of nitrogen sources on pathogenicity were determined in vitro, glucosamine sulfate and ammonium sulfate showed significant reduction of disease index on faba bean germinated seeds put on mycelial hyphal growth (2.3 and 2.6, respectively) compared with sodium nitrate (5.0). Aspartic acid, phenylalanine and peptone showed the same effect on disease index as NaNO3 (Figure 2)
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