الفهرس 
Saline soils definitionOnly 14 pages are availabe for public view
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Abstract
In this study, several fungi were found in the rhizosphere of cotton plants grown in saline soil. These fungi were isolated and identified to species level, and then screened for their potentially to antagonize pathogenic fungi causing cotton diseases in vitro. These species assayed also for their role in controlling infection of cotton plants by soil borne pathogenic fungi, improving cotton plant growth and increasing yield production under greenhouse conditions.
The selected antagonistic fungal species were tested to study their ability to antagonize the soil borne pathogenic fungi that caused cotton damping-off and root rot diseases under different NaCl concentrations.
Briefly, our results can be summarized in the following points:
1- Four soil borne pathogenic fungi, Fusarium moniliforme, F. oxysporum, F. solani and Rhizoctonia solani were isolated from naturally diseased cotton plants (showing symptoms of damping-off and root rot diseases) grown in saline soil.
2- Fifty eight fungal species belonging to 18 genera were isolated from rhizosphere of saline soil of El-Behera and El-Fayoum governorates. Aspergillus and Penicillium were the most prominent among other isolates where both quantitative (1420 and 541 cfu respectively) and qualitative counts with species richness 25 and 10 respectively.
3- In vitro antagonistic activity of 58 fungal isolates against the pathogenic fungi (F. moniliforme, F. oxysporum, F. solani and R. solani) indicated that only 5 rhizosphere fungal isolates (Aspergillus carneus, Cephalosporium acremonium, Penicillium implicatum, Penicillium madriti and Trichoderma lignorum) showed the highest inhibitory activity against the tested pathogens growth and the results showed that:
a- T. lignorum was found to have the most potent and remarkable antagonistic activities causing the highest percentage of inhibition to the tested pathogens and the maximum percentage of inhibition was obtained with R. solani (89.36%).
b- C. acremonium followed T. lignorum in inhibition of growth of F. moniliforme, F. oxysporum and R. solani with values of 54.05%, 48.83% and 44.68% respectively. While, P. madriti followed T. lignorum in case of F. solani (50%).
c- P. implicatum was the least inhibitory bioagents to all pathogens tested and gave the lowest inhibitory effect against R. solani (19.14%).
4- Greenhouse experiments
a- Greenhouse tests on the study of the effect of the selected rhizosphere fungi on cotton damping-off revealed the following:
(i) The presence of pathogenic fungi in the saline soil led to increase in the percentage of pre- and post-emergence damping-off.
(ii) C. acremonium and T. lignorum were the most efficient in controlling both pre- and post-emergence damping-off caused by F. moniliforme, F. oxysporum and F. solani while C. acremonium and P. implicatum gave the highest reduction values of pre-emergence and post-emergence damping-off caused by R. solani.
b- Greenhouse tests also revealed that the selected rhizosphere fungi were effective in reducing cotton diseases caused by pathogenic fungi and showed variable values of percentage of disease control and indicated that:
(i) P. madriti gave the highest value of disease control against with F. moniliforme and F. solani with percentage of 83.33% and 75% respectively.
(ii) T. lignorum was the superior in controlling cotton diseases against F. oxysporum and R. solani with a percentage value of 75% against both pathogens.
(iii) A. carneus was the least antagonizing species against both F. moniliforme and F. oxysporum with disease control percentages of 47.22% and 44.44% respectively, while P. implicatum gave the lowest percentage of disease control against F. solani and R. solani with percentages of 33.33% and 38.88% respectively.
c- Greenhouse tests also include the study of the effect of the selected fungal species on some growth parameters of cotton plants grown in saline soil and results showed their significant role in increasing the tested growth parameters of cotton plants which included: shoot height, root length and fresh and dry weights of shoots and roots. The relatively healthy appearance in the morphological feature of cotton plants was associated with the presence of antagonistic fungi in saline soil. Generally, P. implicatum and P. madriti gave the highest values of most parameters tested with various pathogens while, A. carneus and C. acremonium gave the lower values.
5- Some physiological studies were carried out with the most potent selected fungi against cotton pathogens in vitro and the results showed that:
a- The effect of different NaCl concentrations (0 ppm, 500 ppm, 1000 ppm, 2500 ppm, 5000 ppm and 10000 ppm) on the antagonistic activity of C. acremonium and T. lignorum. T. lignorum is most suppressive on the growth of cotton pathogenic fungi followed by C. acremonium under the same NaCl concentrations. Also, increasing NaCl concentrations did not show significant change in antagonistic activity of two selected fungi.
b- The effect of different NaCl concentrations (0 ppm, 500 ppm, 1000 ppm, 2500 ppm, 5000 ppm and 10000 ppm) on the production of metabolites by C. acremonium and T. lignorum against cotton pathogens showed that the toxic effect of C. acremonium metabolites was disappeared at all NaCl concentrations in case of R. solani while metabolites effect of T. lignorum was disappeared with increasing NaCl concentrations in case of F. moniliforme, F. oxysporum and F. solani but R. solani was the most sensitive to metabolites of T. lignorum.
c- Effect of different NaCl concentrations (0 ppm, 500 ppm, 1000 ppm, 2500 ppm, 5000 ppm and 10000 ppm) on the production of some enzymes by C. acremonium and T. lignorum indicated that activity of both glucanase and chitinase of both selected fungi were not affected by increasing NaCl concentrations.