DIAZOTROPH – BIOAGENT – PATHOGEN PANORAMA TOWARDS THE PRODUCTION OF ENVIRONMENTALLY SAFED CUCUMBER | ||||
| Journal of Agricultural Chemistry and Biotechnology | ||||
| Article 1, Volume 32, Issue 5, May 2007, Page 3693-3709 PDF (925.85 K) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/jacb.2007.201167 | ||||
 View on SCiNiTO | ||||
| Authors | ||||
| Heba E. Ramadan1; M. A. Ali2; Heba Shehata3; M. El-Kattan1; M. Fayez2 | ||||
| 1Biological Agricultural Research Dept., Central Laboratory for Agricultural Climate (CLAC). Agric. Research Center, Giza, Egypt. | ||||
| 2Agric. Microbiol. Dept., Fac. Of Agric., Cairo Univ., Giza, Egypt. | ||||
| 3Soils, Water and Environment Research Institute. Agric. Research Center, Giza, Egypt. | ||||
| Abstract | ||||
| The interactions among some bacterial bioagents, diazotrophs and phytopathogenic fungi were in vitro examined adopting the dual plate culture technique. Pseudomonas aurogonosa inhibited all the examined diazotrophs with an average inhibition zone measured 8 mm in diameter. In contrast, all diazotrophs could persist the antagonistic effect of Pseudomonas putida. Azotobacter chroococcum was the most sensitive to mixed cultivation with the bioagents wherease Bacillus polymyxa was the most tolerant. The bioagents antagonized all the examined fungal pathogens. Pseudomonas fluorescense exhibited the highest antagonistic capabilities against all pathogens with an average inhibition zone diameter of 21 mm followed by Bacillus subtilis (A) and (B). Interestingly, the examined diazotrophs suppressed growth of the pathogens; the measured inhibition zones averaged 12, 9 and 9 in diameter with Azotobacter chroococcum, Azospirillum brasilense and Bacillus polymyxa, respectively. The bioagents and diazotrophs were in vitro screened for IAA, gibberellins, sidrophores and hydrogen cyanide production. All the examined bacteria were active producers of IAA, gibberellins and siderophores, while hydrogen cyanide was exclusively detected with the bacteria of the genus Pseudomonas. In the greenhouse, the bioagents and diazotrophs improved plant survival, shoot biomass, nitrogen uptake and yield of cucumber plants. The improvements in the measured parameters were more pronounced when the bioagent mixture, composite of diazotrophs and their combinations were used for combating the root – rot disease in cucumber. With these inocula, the disease incidence was diminished to a minimum of 10 % whether the soil was infested with the pathogens or not. Shoot – dry matter production by cucumber plants was greatly affected by all inocula particularly, when both bacterial groups were combined in an inoculum. Such inoculum increased shoot biomass by 145 and 94 % over control plants in plain and fungi–infested soil, respectively. Moreover, the yield was maximized to reach < 2 and 4-folds higher than control plants grown with or without fungi, respectively. The obtained results refer to a possible integration of the examined diazotrophs as biofertilizers and bioagents in a combined inoculum for biological control of root–rot disease and improved growth and yield of cucumber plants under greenhouse conditions. | ||||
| Keywords | ||||
| Diazotrophs; bacterial biagents; phytopathogenic fungi; interactions; cucmber growth; yield and root-rot incidence | ||||
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