الفهرس 
The role of plant growth promoting rhizobacteria (PGPR) as a bio-control agents in plants.Only 14 pages are availabe for public view
 |  | from | 193 |  |  |
| | | from | 193 | | |
Abstract
Tomato (Lycopersicon esculentum Mill.) is considered a main contributor to food of humans. It is mainly grown in all countries whether in fields or protected cultures. Tomato is considered one of the most essential vegetable crops. It is grown in Egypt in different seasons throughout the year basically in newly reclaimed desert lands. Tomatoes are known that a protective supplementary food because they are considered a rich source of minerals such as iron and phosphorus, organic acids and essential amino acids . As well as a rich source of vitamins such as vitamin A which helps in bone growth, cells division, regulation of immune system and maintaining linings of eyes. Also, vitamin C is important in forming collagen and protein that enters into bone structures , cartilages , muscles and blood vessels . It also helps maintaining teeth and aids in the absorption of iron. In addition to, they contain some antioxidant compounds such as Lycopene that protects from carcinogenic diseases.
Tomato plants are infected by several diseases such as fungal, bacterial , viral & nematode diseases which cause fatal losses to this crop.
Management of plant diseases produced by parasitic organisms has come to be a challenging task to the researchers for sustainable agriculture. Root-knot nematodes, Meloidogyne
spp. are considered one of the most economically important pest because their damage , infection level , wide host range and minimize the quality and quantity of the crop . So it was used several chemical compounds to fight this nematode and eliminate it. As a result of this excessive use which led to occur most harms to human, animals and environment. To avoid this, security and friendly environment methods were searched such as plant growth promoting rhizobacteria (PGPR).
Rhizobacteria is naturally exists in soil that aggressively colonizes plant roots and benefits plants by growth promotion and augments the productivity and immunity. Rhizobacteria is classified as plant health-promoting rhizobacteria (PHPR) or plant growth-promoting rhizobacteria (PGPR). PGPR directly affects the plant growth by fixing the atmospheric nitrogen in soil, solubilizing the minerals and facilitating uptake them by plant and producing phytohormones and siderophores which helps chelating of iron and makes it available to plant roots , on the other hand indirectly by secreting of antibiotics, organic acids, lytic enzymes and inducing the systemic resistance of plant which makes it a safe alternative and environmentally friendly instead of the nematicides.
Formulation of (PGPR) as carriers is a promising industrial art for converting it from laboratory form to a commercial field product. Immobilization of bacterial cells into
polymer matrix has proved to be beneficial over direct soil inoculation.
The major objectives of this work were:
1- Evaluation four plant growth promoting rhizobacteria Pseudomonas fluorescens, Azospirillum brasilense, Azotobacter chroococcum & Bacillus megaterium as bio- control agents against Meloidogyne spp. in vitro and in vivo on tomato plants.
2- Select the best active rhizobacteria and encapsulated it by sodium alginate.
3- Evaluation encapsulated B. megaterium by using it as bio- control agents against Meloidogyne spp. on tomato plants under greenhouse conditions.
4- Assessing of B. megaterium viability inside the capsules at 150 days in vitro.
5- Assessing of this bacterium for secreting of protease enzyme in vitro.
This study can be summarized as follows :
1- Experimentally, the culture broth of four bacterial isolates
i.e. P. fluorescens, A. brasilense, A. chroococcum & B. megaterium was used to test their effect on egg hatching and juveniles mortality of Meloidogyne spp. under room temperature after 24,48,72 & 168h of exposure.
2- The present results exhibited that all bacterial isolates affected nematode eggs and juveniles especially B.megaterium where fulfilled the least percentage of egg hatching and the highest percentage of juveniles mortality after 168 h of exposure by
17.3 & 92 %, respectively compared to control.
3- This has been inferred through doing an experimentally test for this bacterium on King’s B medium in Petri dishes and incubated it for 48 h at 27ċ where the results exhibited that this bacterium had the ability to analyze the protein existed in this medium by exhibiting a clear halo zone around the bacterial colony.
4- The same four bacterial isolates were used as a culture broth at three application times ( one week before, at the same time and one week after ) of nematode inoculation to study their effect on Meloidogyne spp. on tomato plants under greenhouse conditions.
5- These results exhibited that all bacterial isolates significantly affected the nematode and vegetative parameters especially during adding them at one week before of nematode inoculation where B.megaterium fulfilled the highest reduction percentages of nematode parameters and highest increase in vegetative parameters , antioxidant enzymes and pigments concentrations.
6- Other experiment was done under greenhouse conditions by applying B.megaterium in two forms i.e. liquid and capsules contained and uncontained humic acid at the rate of 3,5,10 ml or capsules /plant to know which two forms are the most effect .
7- These present results exhibited that both forms fulfilled a significant effect in inhibiting the nematode parameters and increasing the vegetative parameters of plant but using the capsules is better than a liquid form.
8- Applying this bacterium at the rate of 10 capsules / plant fulfilled the highest reduction percentage to nematode parameters and highest increase percentage in vegetative parameters, antioxidant enzymes (peroxidase & polyphenol oxidase) and pigments concentrations especially during adding humic acid.
9- Other experimental test was done to study the effect of storage time (150 days) on the viability of bacteria inside capsules, where the present results exhibited that capsules contained humic acid preserved the bacterial viability for a long time arrived at 150 days whereas the capsules uncontained this component preserved the viability for just 90 days then the viability gradually declined.
10- We recommended with using of this group of bacteria especially in capsules form with adding a catalyst component such as humic acid to control the pests and pathogens
principally root-knot nematodes because it is considered as a safe alternative and environmentally friendly.