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Title: IDENTIFICATION AND SELECTION OF SALT- AND HEAT-TOLERANT LEUCAENA-NODULATINGRHIZOBIUM

Author
item HASHEM, F
item SWELIM, D
item Kuykendall, Larry

Submitted to: Biology and Fertility of Soils
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/17/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Although Rhizobium-legume symbioses are important for their input of biologically fixed nitrogen, salinity and elevated temperature in arid and semi-arid areas limit both Rhizobium effectiveness and plant growth and productivity. Sixteen Rhizobium sp. (Leucaena) strains were studied for the degree of salt and heat tolerance and in their symbiotic ability with Leucaena leucocephala under adverse conditions of saline and or elevated temperatures. Broad-host-range Rhizobium strains DS 78 and DS 158 that effectively nodulate Leucaena under these adverse environmental conditions were successfully identified. These strains could be used as inoculants by growers of Leucaena where the soil is highly saline or where high temperatures persist, or both.

Technical Abstract: Rhizobium-legume symbioses are important for their nitrogen input, but salinity and elevated temperature in arid and semi- arid areas limit both Rhizobium effectiveness and plant growth and productivity. Sixteen Rhizobium sp.(Leucaena) strains varied in the degree of salt tolerance and in their symbiotic ability with with Leucaena leucocephala under saline conditions. Three strains were tolerant of >3% NaCl. L. leucocephala grown in the greenhouse at concentrations of NaCl up to 1.00% and inoculated either with strain DS 78 or strain DS 158 displayed significantly better growth than those plants grown at the same levels of salinity and inoculated with reference strain TAL 583. Although nine of the Rhizobium strains grew at 42 degrees C, their generation times were lengthened two- to four-fold. When temperature was elevated from 30 to 42 degrees C, nodule number and mass, nitrogenase activities and shoot dry weight of plants inoculated with strains DS 78, DS 157 and DS 158 significantly increased, whereas these parameters declined in plants inoculated with strain TAL 583. Broad-host-range Rhizobium strains that effectively nodulate Leucaena under adverse environmental conditions were identified.