|
Genetic
identification and symbiotic efficiency of Sinorhizobium
meliloti indigenous to Saudi Arabian soils
Abdel-Aziz R.
A.*, Al-Barakah F. N. and Al-Asmary H. M.
Department of Soil Science, College of Food and Agricultural
Science, King Saud, University, P.O. Box, 2460, Riyadh
11451, Saudi Arabia.
*Corresponding author. E-mail:
abdel_aziz_reda@hotmail.com.
Fax: 00966 1 4678440.
Accepted 26 June, 2008 |
|
Soil bacteria Sinorhizobium meliloti are of
enormous agricultural value, because of their ability to fix
atmospheric nitrogen in symbiosis with an important forage
crop legume-alfalfa. The main aim of this study was (i) to
isolate indigenous S. meliloti strains from different
field sites in Saudi Arabia, (ii) to assess genetic
diversity and genetic relationships amongst strains of
natural populations and (iii) to provide information about
nodulation and symbiotic efficiency of indigenous S.
melitloti strains. Nineteen strains isolated from
alfalfa nodules collected from different field sites and one
reference strain were analyzed. Genetic characterization by
rep-PCR and RAPD-PCR was applied to study the status of
S. melitloti populations inhabiting nodules of alfalfa.
Cluster analysis of rep-PCR profiles showed significant
differences among S. meliloti isolates. Both methods
resulted in almost identical grouping of strains. Among
indigenous strains two divergent groups could be determined.
The biggest differences were detected among the reference
strains along with two local isolates and all field
isolates. Quantitative expression of symbiotic efficiency
was evaluated by measurement of total nitrogen in plants and
dry matter yield of plants. All strains nodulated alfalfa
cultivar CAF 101 but with different efficiency. Significant
differences in dry mater yield of alfalfa as well as total
nitrogen content were determined depending on the strain
used. The results indicate that sixty one percent of
indigenous S. meliloti strains can be characterized
as low efficient strains.
Key words:
Alfalfa, Sinorhizobium meliloti, symbiotic
efficiency, genetic diversity. |
