Effect of biofertilization and organic manuring on soil dehydrogenase activity, macronutrients and essential oil content of marjoram

Two field experiments were carried out at an organic farm [Minoufia Governorate] during 2005- 2006 and 2006-2007 seasons to study the interaction effect of biofertilization and organic manuring on dehydrogenase, polyphenol oxidase and peroxidase activity, macronutrients uptake, oil yield and oil composition of marjoram. Greater activities of dehydrogenase, peroxidase and polyphenol oxidase were obtained in soil and marjoram treated with combination of biofertilizers and organic manure than soil treated with biofertilizers or organic manure. The greatest activities of peroxidase and polyphenol oxidase were obtained with the treatment of biofertilization combined with full dose of organic manure. Similar results trend was observed with N, P and K uptake because N, P and K uptake by marjoram were greater with dual application of biofertilization and organic manure than other treatments. There is no significant difference between oil yield obtained with chemical fertilization treatment and biofertilizers combined with full dose of organic manure treatment. Fourteen compounds, accounting for more than 97% of the total volatiles components in most marjoram samples were detected and identified. Dual application of organic manure and biofertilization to soil and marjoram produced maximum percent of terpincn-4-ol [the major compound in marjoram oil] compound in marjoram

Optimal environmental conditions for production of plant growth regulators by rizobacteria

This study was carried out to isolate and identify some plant growth promoting rhizobacteria [PGPR]. The optimum incubation condition, i.e. temperature and fermentation period, for plant growth regulators [PGRs] production were limited. Obtained data revealed that rhizosphere of cereal crops showed higher PGPR isolates compared to rhizosphere of other crops. Among the examined isolates, fifteen were highly efficient for auxins production. The most potent isolates for indoles production were chosen and these isolates were identified as Azotobacter chroococcum [R19] and Bacillus megaterium var, phosphaticum [R44]. The optimum incubation temperature for highest production of auxins, gibberellic acid [GA[3]] and cytokinins were 32 and 30°C for A. chroococcum and B. megaterium var. phosphaticum, respectively. In addition, the highest production of these phytohormones were obtained by the two strains after four and two days fermentation period, respectively

Effect of carbon source and precursors on the production of plant growth regulators by azotobacter chroococcum [R19] and bacillus megaterium var. phosphaticum [R44]

An experiment was carried out to examine the effect of carbon source, tryptophan and adenine concentrations on the production of growth regulators by A. chroococcum [R19] and B. megaterium var. phosphaticum [R44]. Mannitol and glucose were the best carbon sources for the production of plant growth regulators [PGRs] by A. chroococcum and B. megaterium var. phosphaticum, respectively. A. chroococcum produced higher amounts of zeatin and kinetin compared to those produced by B. megaterium var. phosphaticum while B. megaterium var. phosphaticum produced higher amounts of [9R] benzyl adenine and [9G] bcnzyl adenine compared with those produced by A. chroococcum. Production of auxins, gibberellic acid [GA[3]] and cytokinins was increased with increasing tryptophan concentration. The highest amounts of PGRs produced by the two strains were obtained with tryptophan at 1000 micro M. Highest amounts of PGRs produced by A. chroococcum and B. megaterium var. phosphaticum at 10 and 100 micro M of adenine, respectively. Also, the produced amounts of gibberellic acid and cytokinin than that produced by B. megaterium var. phosphaticum. Generally, obtained data showed that the application of the optimal conditions together gave highest amounts of PGRs as compared with the other individual factors. This result is logic and was anticipated

Interaction between growth regulators-producing bacteria and root-rot fungi on tomato growth

The current study was carried out to study the interaction effect between plant growth promoting rhizobacteria [PGPR] and soil-borne pathogenic fungi on growth performance of tomato. PGPRs Azotobacter chroococcum [R19] and Bacillus megaterium var. phosphaticum [R44] strains used in the current study were isolated and identified in previous research by the same authors. Results obtained showed that A. chroococcum and B. megaterium var. phosphaticum gave high suppression against tomato root pathogenic fungi, i.e Fusarium oxysporum f.sp lycopersici and Fusarium solani. In vitro tests, clear zones around PGPR colonies can be attributed to the production of antibiotics-like substances, siderophores and cyanogens by suppressive PGPR strains. A lower percentage of tomato plants inoculated with a mixture of A. chroococcum and B. megaterium var. phosphaticum were infected than those inoculated with individual PGPRs . Growth characteristics, macro-nutrient content, endogenous phytohormones and photosynthetic pigments of tomato were significantly increased in the dual inoculated treatments compared to plants inoculated with either A. chroococcum or B. megaterium var. phosphaticum singly