الفهرس 
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Effect of bioagents on fungal growth of pathogens in vitro.Only 14 pages are availabe for public view
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Abstract
The disease of root rot in the grain of the black cumin caused by some species of Fusarium spp. is one of the most serious diseases affecting the plants of black cumin in the Arab Republic of Egypt where it leads to a significant reduction in the seed production and fixed and volatile oilsquantity.
Several recommendations for controlingFusarium spp. fungi through the use of Agricultural operations, chemical control and cultivation of resistant varieties. The effect of these processes is limited, because the chlamydospores of the fusarium remain long time in the soil.
This study was conducted with the aim of:-
Isolation and definition of plant growth-promoting rhizobacteria (PGPR) of rhizosphere of the black cumin plants,in addition to assessing the capacity of these isolates on Promoting growth and reduce the prevalence of the root rot diseaseunder greenhouse and field conditions,study of the effect of (PGPR) on pathogens in vitro, and their impact on vegetative growth and seed production,as well as the quantity of fixed and volatile oils.
Results of this study can be summarized as follows:
1- Eight fungal isolates were obtained from diseased plants collected from Assiut Governorate. These isolates were found to follow the genus Fusarium sp. They were defined as fourFusarium camptoceras, three F. solani and one isolate Fusarium lateritium.
2- Pathogencity tests indicated that all tested fungal isolates were able to infect plants causing symptoms of root rot in black cumin.
3- The isolated Fusarium camptoceras No.1 gave the highest percentage of infection by (50%), followed by isolates 3 and 6 F. solani and F. camptoceras (15 % and 17%) while isolate No. (8) Fusarium lateritium gave (5%), other isolates gave moderate effect.
4- Fifteen bacterial isolates were obtained from rizosphere of black cumin plants. Antagonistic capability of 15 isolates (PGPR) was tested in vitro. against growth of three isolates of Fusarium spp. Results showed that isolate P. fluorescens No.1, P. fluorescens No.2, Bacillus simplex No.1, Bacillus simplex No.2 and Pseudomanas earuginosa gave the highest effect (72.88, 71.66, 65,33, 64,44 and 63,33) while isolates Nos. (8 and 11) gave the lowest effect inhibition (44.30and 34,60) while other isolates gave medium effect.
5- Treatment of the black cumin seeds with (PGPR) as a suspension and cultivated in the soil infected with fungi pathogens under greenhouse gave the lowest percentage of infection.The highest reduction in % infection was recorded by treatments B. simplex No.1/F. camptoceras and P. aeruginosa / F. lateritiumcompared to infected control.Alsogavetreatments B. simplex No.1/ F. lateritium and B. simplex No.2 / F. solani as aformulation gave the highest reduction of % infection was recorded.
6- Treatment of the black cumin seeds with (PGPR) as a suspension and cultivated in the soil infested with fungal pathoges under greenhouse gave the lowest disease severity P. fluorescens No.2/ F. camptoceras, gave highest reduction of the disease severity. Alsotreatments of P. fluorescens No.1, B. simplex No.2, P. aeruginosa, and P. fluorescens No.2, gavethe highest reduction ofthe disease severity as aformulation was recorded.
7- Proved the results showed that black cumin seeds treated by bioagents (PGPR) as a suspension gave positive effect in reducing the number fungalgrowth in vitro. The treatments, B. simplex No.1 with F. camptoceras, F. solani, and F. lateritium gave the lower effect on number of colony (28.30, 27.00 and 26.33), while the treatment ,B.simplex No.2/ F. solanias aformulation gave highest reduction of number fungalmass(6.00) and the B. simplex No.2/ F. lateritium gave less fungal mass number (21.33).
8- PGPR increased the growth of plants roots and foliar length, all bioagents as a suspension or formulation significantly increased the root and foliar length as compared with infected control.
9- All bioagents treated as a suspension increased the root fresh weight, the treated with P. fluorescens No.2 gave the highest root fresh weight (0.88) gm/plant as compared to infected control (0.35). Also B. simplex No.1 gave the highest root fresh weight when treated as a formulation (0.35) gm/plant as compared to control (0.19) gm/plant.
10- Seeds black cumin plant treated by isolate P. fluorescens No.2 as a suspension gave the highest foliarfresh weight 8.04 .However the other isolates significantly increased the foliar fresh weight. Also, P. fluorescens No.1and B. simplexNo.1 as formulation increase the foliar fresh weight significantly as compared to infected control
11- Seeds of black cumin plant treated by bioagents isolate B. simplex No.1as a suspension gave the highest foliar dry weight (2.27). The other treatments gave average effect in the increasing of foliar dry weight Application of P. fluorescens No.1 as a formulation gave the highest foliar dry weight (1.94)followed by otherisolates bacterial on foliar dry weight.
12- All (PGPR) isolates have ability to phosphate solubilizatation with different degree among them. Pseudomanas earuginosa gave highest amount of phosphate solubilization followed by P. fluorescens No.2 and Bacillus simplex No.1, while P. fluorescens No.1 and Bacillus simplex No.1 show a weak productivity.
13- All PGPR isolates have ability to produce siderophores with different degrees among them. B. subtilis No.1 gave highest amount of siderophores followed by P. fluorescens No.1 B. simplex No.2 and P. earuginosa.HoweverP. fluorescens No.1 show a weak produce of siderophores.
14- The four isolates of have ability to produce (IAA) with different degree among them self. Bacillus simplex No.1 gave highest amount of indole acetic acid (IAA) followed by P. florecens No.2 and Bacillus simplex No.2.However P. florecens No.1 show a weak whereas P. earuginosa scored as nil since there is no production of (IAA) based on the color development.
15- Results also showed that all treatments as a suspensionhave reduced the root rot, disease severity % compared to infected control except the following treatments, B. simplex No.1/ F. lateritiumand B. simplex No.2/ F. lateritium, Also indicate that all tested bacterial isolates as a formulation effective on disease severity of black cumin when treated, which reduced the disease severity without significant difference between them, except isolate B. simplex No.2which gave the highest reductionof disease severity.
16- All bacterial isolates gave an increase in the proportion of fixed and volatile oils in varying proportions as compared to infected control. The results showed that P. floresense No.2 (suspension or formulation) gave the highest amount of volatile oil (0.90).|HoweverP. floresense No.1 with F. solani fungi showed the lowest amount of volatile oil(0.60).Under electronic microscope, all isolates distorted the fungus mycelium, shrink and shrivel of pathogen hyphae, hyphal lysis and breakage and colonization over the hyphae.