ENVIRONMENTAL-FACTORS INFLUENCING THE SURVIVAL OF RHIZOBIUM-LEGUMINOSARUM BV VICEAE

Investigations were carried out to monitor the sensitivity of Rhizobiu m leguminosarum bv. viceae strains to various environmental stress-fac tors (salinity, pH, Al3+, Ca2+, Mg2+) and select them as potential can didates for Vicia faba inoculation. In the range between pH 5.0 and 10 .0, the salt effect of 10-500 mM NaCl, Ca2+, Mg2+ (as chlorides and su lphates), Al2O3 and KAl(SO4)(2) (25-400 mu M) were tested in modified yeast-mannitol (YEM) liquid medium. Cell density of the suspensions in oculated with R. leguminosarum bv. viceae strains (initial cell-number 10(6) CFU/ml) were measured spectrophotometrically after 48 h incubat ion in a rotary shaker (rpm 150) at 28 degrees C. Data of optical dens ity (OD550) are shown as percent of control (inoculated, free from tre atments, pH 7.0) tubes. It was established, that results of tolerancy were in agreement with those found earlier for Rhizobium sensitivity. Strain of Lobab Z (isolated in Hungary) however proved to have an espe cially outstanding survival in any media tested in vitro. Lowest obser ved effect concentrations (LOECs) were: 500 mM NaCl, 200 mu M Al3+ (as Al2O3 or KAl(SO4)(2)), 50-100 mM Mg2+, and 200-300 mM Ca2+. Far the A l3+, Ca2+ and Mg2+ cations, there was no variation between the stress- effect of sulphate and chloride anions. Both forms of Ca2+, however si gnificantly reduced the growth potential of R. leguminosarum bv. vicea e strains.