The rhizosphere of four host desert plants (Hordeum murinum,
M. crystallinum, Z. album and Stipagrostis scoparia) and one
cultivated Nile valley crop (Hordeum vulgare) was examined.
Total RMO in the ecto- and endo-rhizospheres were determined
using the ice plant juice (crude juice diluted 1:40 distilled
water, v/v)-based agar medium and were compared with the
reference media of nutrient agar, soil extract agar CCM.
Ecto-rhizosphere samples were prepared [13] by transferring
sufficient portions of root systems with closely adhering soil
into sampling bottles containing the basal salt solution of
CCM, as diluent. Bottles were shaken for 30 min and serial
dilutions were prepared. The endo-rhizosphere samples were
prepared [17] by washing another set of roots with tap water,
then with 95% ethanol for 5–10 s, followed by 3% sodium
hypochlorite for 1.5 h. Surface sterilized roots were then thoroughly
washed with sterile water and crushed for 5 min in a
Waring blender with adequate volume of basal salts of CCM
medium. Further serial dilutions were prepared, and suitable
dilutions of both spheres were surface-inoculated on agar
plates prepared from all tested culture media. Incubation took
place at 30 C for 2–7 days and cfu were counted. Dry weights
for suspended roots (80 C) and rhizosphere soil (105 C) were
determined