Natural endophytic association between Rhizobium leguminosarum bv. trifolii and rice roots and assessment of its potential to promote rice growth

The beneficial plant growth-promoting association of Rhizobium leguminosarum bv. trifolii with rice roots

“…We took an ecological approach involving two cycles of field and laboratory studies to detect, enumerate, and isolate rhizobial endophytes from surface-sterilized roots of field-grown rice to confirm our previous finding (Yanni et al 1997) and to expand the diversity of our culture collection of rice-adapted rhizobia. Rice plants of approximately the same height were sampled at five different field sites during two rotations with berseem clover in the Nile delta.…”

“…Methods previously described (Yanni et al 1997) were used to enumerate, isolate and characterize the natural endophytic populations of clover-nodulating rhizobia within field-grown surface-sterilized rice roots. The diversity and relatedness of strains was assessed by pattern analysis of their plasmid profiles and BOX-polymerase chain reaction (PCR) genomic fingerprints followed by computer-assisted cluster analysis (Espuny et al 1987;Rademaker et al 1998;Rademaker et al 1999).…”

“…Rice was grown in either large enclosed test tubes (Yanni et al 1997) or Sarstedt pre-sterilized, 120-mL plastic cylinder jars (Prayitno et al 1999) In some experiments, the solidified growth medium in the culture vessels was overlaid with sterilized acid-washed quartz sand (ca 5 g for tube cultures and 22 g for jars), and 5 mL sterile water. Other variables examined included plant nutrient concentration (half-vs full-strength Hoagland's No.…”

“…Growth and yield parameters plus calculations of the agronomic fertilizer N-use efficiency (kg grain yield per kg fertilizer N applied) were subjected to statistical analysis with the rates of fertilizer N as the main-plot treatments and inoculation with the rhizobial rice-root endophytes as the subplot treatments. Significances of the mean squares of the main and subplot treatments were compared using the F-test and the least significant differences between means were calculated using the t-values at 95 and 99% confidence levels as described previously (Yanni et al 1997).…”

“…trifolii, and rice roots, which develops intimately without induction of root nodules or obvious disease symptoms on this cereal host (Yanni et al 1997;. Studies described in this paper include the natural abundance and diversity of rhizobial endophytes within field-grown rice roots, their expression and possible underlying mechanisms of plant growth-promoting (PGP) activity, their patterns of rice root colonization and ecophysiological activities, and their performance under field conditions as potential biofertilizer inoculants capable of increasing rice grain yield and agronomic fertilizer N-use efficiency, thus reducing dependence on chemical fertilizer inputs.…”