الفهرس 
REVIEW OF LITERATUREOnly 14 pages are availabe for public view
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Abstract
SUMMARY
Microorganisms that live in close association with the plant roots play a significant role in stress alleviation in crops, especially those grown in saline soils due to their unique properties of tolerance to extremities. About 2–5% of rhizobacteria, when reintroduced to the soil by plant inoculation in the rhizosphere containing competitive microflora, exert a beneficial effect on plant growth. these types of microorganisms are termed plant-growth-promoting rhizobacteria (PGPR).
Using plant-growth-promoting rhizobacteria exhibited promising alternative strategies to overcome the limitations of crop productivity caused by salt stress and they brought better plant health and protection. Additionally, they are environmentally friendly and cost effective. Which applied as bio fertilizer in salinity soils cultivated by sugar beet under green house and shows effective results.
This study included the following points:
1.Isolation of Plant Growth Promoting Rhizobacteria.
Fifteen bacterial isolates were successfully isolated and purified from the collected soil samples. The rhizobacterial isolates were categorized according to their isolation media and the EC of the soil samples that was isolated from. The examined isolates revealed clear morphological and biochemical properties belong to the members of the genus Bacillus B.M9, B.K12, B.E15 and B.S20, the genus Stenotrophomonas coded X.M9, X.K12, X.E15 and X.S20, the genus Azotobacter sp. the isolates were coded as A.M9, A.K12, A.E15 and A.S20, and the genus Pseudomonas were coded P.M9, P.K12, and P.S20. The growth performance of selected isolates was done in the form of microbial optical density as a function of time. Effect of different levels of salinity on the growth performance of the tested isolates was performed.
2.The growth performance of selected isolates.
Data presented revealed the growth pattern of eight isolates for Bacillus sp. and Stenotrophomonas sp. in the form of microbial optical density as a function of time during 30 hr. at 30ºC.The growth of the tested isolates for Bacillus sp. exhibited the maximum microbial growth of 0.195 OD for isolate B.M9 of after 21 hour and 0.135, 0.173 OD for isolate B.K12, and B.E15 after 18 hours. While the isolate B.S20 revealed the maximum growth of 0.183 OD after 15 hours and the isolates X.S20, X.E15, X.K12 and X.M9 for Stenotrophomonas sp. The maximum microbial growth of 0.243, 0.146, 0.277 and 0.264 OD respectively were recorded with in all isolates after 15hr.
Data show the growth pattern of seven isolates of Azotobacter isolates and Pseudomonas isolates in the form of culture optical density as a function of time during five days at 30ºC. Maximum growth was recorded within all Azotobacter isolates after three days being 0.210,0.105, 0.170, and 0.190 OD was recorded for isolates A.M9, A.K12, A.E15, and A.S20, respectively. Also, all Pseudomonas tested isolates P.M9, P.K12 and P.S20 were recorded after three maximum growth of 0.189, 0.164 and 0.164 OD respectively.
3. Growth performance of the tested isolates on different levels of salinity.
The Bacillus isolates B.K12 and B.M9 revealed the highest growth of 0.434 and 1.167 OD on the medium of EC5 respectively and recorded decrease in their growth by increasing the concentration of NaCl in the medium. The isolate Stenotrophomonas sp. X.M9 exhibited the highest growth performance in the form of OD in most salt concentrations compared to all tested isolates being 1.376, 1.326, 1.292, 1.053and 1.059 OD respectively. The isolate Azotobacter sp. AS20 exhibited the highest growth in the form of OD in all salt concentrations compared to all test isolates. The growth of the isolates A.S20, A.M9 decreased by increasing the concentration of NaCl as the highest growth was recorded with in EC 5 of 0.329 and 0.107 OD respectively. The Pseudomonas isolate P.S20 reveals the highest growth of 1.986 OD on the medium of EC15 and revealed decrease in the growth by increasing the concentration of NaCl in the medium. The isolate P.K12, P.M9 revealed the highest growth of 1.686 and 1.684 OD on the medium of EC 20 in respective order.
4. Effect of different levels of pH on the growth performance of isolates.
Bacillus isolates B.S20 and B.K12 revealed increasing growth by increasing the pH of the medium up to 6 pH and exhibited a decrease in the growth by increasing the pH up to 10 pH. The Stenotrophomonas isolates X. E15, X. K12 and X.M9 revealed increasing in the growth by increasing the pH up to pH 10. The Azotobacter isolate A.S20 revealed the highest resistance to most of pH levels compared to all tested isolates. The highest growth of the isolates A.S20, A.K12, A.M9 was recorded at the medium adjusted to pH 7 of 0.343, 0.181 and 0.182 OD in respective order. The Pseudomonas sp. isolates P.S20 and P.M9 showed an increase in growth by increasing the pH of the medium up to pH 8 since they showed the highest growth of 0.833 and 1.794 OD, and both showed a decrease in growth by increasing the pH value up to pH 10.
5. Effect the different incubation temperatures on the growth performance of tested isolates.
The optimum temperature for the Bacillus sp. isolate B. S20 and B. M9 was recorded as the highest growth of 1.764 and 1.381 OD at 35 ºC and 25ºC respectively. The optimal growth of the Stenotrophomonas isolates X. S20, X. E15 and X.M9 was 30⁰C. The optimum growth of the Azotobacter sp. isolates A. S20 and A. M9 was recorded as the highest OD values of 0.356 and 0.562, at 30⁰C. The optimum growth of the Pseudomonas isolates s P. K12 and P. S20 was recorded as the highest OD values of 2.059 and 1.960 OD at 30ºC.
6. Effect of different carbon and nitrogen sources on the growth performance of tested isolates.
The Bacillus isolate B.S20 exhibited the highest growth on lactose followed by maltose as carbon sources being 2.00 and 1.927 OD respectively. The Stenotrophomonas isolate X.S20 revealed the highest growth of 0.906 OD on the sucrose followed by lactose of 0.621 OD. The Azotobacter isolate (A.S20, A.E15, A.K12 and A.M9) recorded the highest growth on the mannitol and sucrose as a combination carbon source of 1.370, 1.215, 1.101 and 1.136 OD, followed by starch being 0.862, 0.800, 0.826 and 0.836 OD respectively. The Pseudomonas isolate P.K12 revealed the highest growth on maltose of 2.262 OD . The Bacillus isolate B.S20 and B.E15 revealed the highest growth performance on the beef extracts as nitrogen sources of 1.959 and 2.024 OD respectively. The highest growth of the Stenotrophomonas isolates X.S20 and X.E15 was recorded with in ammonium molybdate of 1.663 and potassium nitrate (KNO3) of 1.455 OD, respectively. The Pseudomonas isolates P.S20, P.k12 and P.M9 exhibited the highest growth performance on peptone extract as nitrogen sources of 2.153, 2.194 and 2.087 OD, respectively.
7. The efficiency of tested isolates in producing plant growth promoters (PGPRs).
All the Bacillus, Stenotrophomenas, Azotobacter and Pseudomonas isolates exhibited the capability to produce plant growth regulators (IAA, Kinetin, Zeatin, ABA and GA3). Generally, all the Azotobacter isolates were able to fix atmospheric nitrogen while only the isolates P.S20 and P.M9 of Pseudomonas sp. were able to fix atmospheric nitrogen. All the Bacillus isolates were able to solubilize potassium and phosphorus. The isolate B.K12 revealed the highest capability to solubilization phosphorus of 204.6 ppm. While The isolate B.E15 revealed the highest capability to solubilization potassium of 1219.75 ppm. All the Stenotrophomonas isolates revealed high capability to solubilize potassium and phosphorus.
8. Identification of the selected isolates.
According to the previous data, the isolates (B.S20, X.M9, A.S20, P.K12 and P.M9) was selected for identification. Using the Blast analysis of the 16S rRNA gene. The isolates (B.S20) was identified as Bacillus spizizenii strain, the isolates (X.M9) was identified as Stenotrophomonas rhizophila strain, the isolates (A.S20) was identified as Azotobacter vinelandii strain, the isolates (P.M9) was identified as Pseudomonas putida strain and the isolates (P.K12) was identified as Pseudomonas aeruginosa strain.
9. Pot experiment.
Effect of the plantation method, different salt concentrations in the irrigation water, and using PGPRs as a biofertilizer on the growth and yield parameters, sucrose % and proline contents of sugar beet cultivated in sandy soil. where showed the combined effect of the plantation method, salt concentration in the irrigation water, and using PGPRs as a biofertilizer revealed the highest significant increase in shoot height of 58 cm, root length of 24.33 cm, and shoot fresh weight of 203.33 g in plants cultivated by seeds, irrigation by tap water and inoculated by PGPRs compared to all the treatments. While the highest significant leaves number of 29.33 was recorded within sugar beet plants cultivated by seedlings, irrigated by tap water and inoculated by PGPRs. While the highest significant increase in root fresh weight of 186.67 g and root diameter of 6.30 cm within plants cultivated by seedling, inoculated by PGPRs and irrigated by tap water (control). The highest significant sucrose percentage of 14.61% was recorded within sugar beet plants cultivated by seedlings, inoculated by PGPRs as a biofertilizers and irrigated by 5000 ppm salt water. While the highest significant proline content of 12.04 mg/g dw was recorded within uninoculated sugar beet plants, cultivated by seedling, and irrigated by 5000 ppm.
At the end of pot experiment reveals the total count of the tested PGPR strains inoculated to sugar beet. Generally, the total count of all tested strains exhibited a decrease in their count by increasing the concentrations of salt in the irrigation water. The strain Stenotrophomonas rhizophila (X.M9) revealed the highest resistance to different salinities when compared to other PGPRs. These findings are consistent with prior research on the impact of various salt concentrations on the development of tested isolates.