Survival of clover rhizobia under drought and heat stress in soil and on arrowleaf clover seed /
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1990.
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| Subjects: | |
| Online Access: | ProQuest, Abstract Link to OAKTrust copy |
| Abstract: | Successful inoculation of arrowleaf clover (Trifolium vesiculosum Savi) is dependent on early nodulation of emerging roots by effective clover rhizobia (Rhizobium leguminosarum biovar trifolii). However, in early fall, when arrowleaf clover is sown, the prevailing environmental conditions often are detrimental to survival of inoculant rhizobia. Additionally, arrowleaf clover seed is toxic to rhizobia. In this study, 150 isolates from 15 field locations in northeast Texas and 10 commercial strains of clover rhizobia were evaluated for tolerance of drought (<-1.5 MPa; 28°C) stress and heat stress (37°C; -0.03 MPa) conditions when incubated for various periods in sterilized soil. Ten soil isolates from each of 15 field locations were obtained from nodules grown aseptically under controlled conditions. No commercial strain was tolerant of either drought or heat stress. Four soil isolates were tolerant of both stresses. Thirty-five soil isolates were tolerant of either drought or heat stress and were characterized into 16 distinct plasmid groups by plasmid profile analysis. Selected soil isolates and commercial strains were examined for identity by multilocus allozyme electrophoresis and were distinct from commercial clover strains. Growth of all commercial clover strains was inhibited by arrowleaf clover seed. Forty-five soil isolates were insensitive to inhibitory substances in arrowleaf clover seed. Single strain peat inoculants prepared using 18 stress tolerant soil isolates and two strains of commercial clover rhizobia were used to inoculate seed or glass beads that were incubated under conditions of heat (37°C), desiccation (75% R.H.) or without environmental stress. Populations measured on glass beads were generally 1.0 log unit greater than on seed. One soil isolate, W-8-1, was tolerant of both drought and heat stresses and possessed reduced sensitivity to inhibitory substances in arrowleaf clover seed. Soil isolate W-8-1 was also symbiotically highly effective. Further research will be necessary to determine how stress tolerant isolates influence the efficacy of inoculation of arrowleaf clover under field conditions. |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Soil science." |
| Physical Description: | xiii, 209 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |