Identification and pathogenicity of Fusarium species associated with cotton seedling roots, and their interactions with biocontrol agents and other soil-borne pathogens /
Fusarium oxysporum, F solani, F. equiseti, F. nygamai, F
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1995.
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| Subjects: | |
| Online Access: | Link to OAKTrust copy http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=742536521&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Fusarium oxysporum, F solani, F. equiseti, F. nygamai, F semitectum and F. moniliforme were recovered from apparently healthy cotton seedling roots growing in soil (Lufkin fine sandy loam) collected from a cotton field. Fusarium oxysporum and F solani were the dominant species. Fusarium nygamai is a new species record for the United States. Pathogenicity tests showed that several F solani and a few F oxysporum isolates were pathogenic to cotton, but F equiseti, F. nygamai or F semitectum were not pathogenic. Fusarium solani was more virulent than F oxysporum to cotton seedlings. Fusarium nygamai produced phytotoxins in selected culture conditions, and symptoms produced by the phytotoxins could be mistaken for pathogenesis. Under growth chamber conditions, the biocontrol agent Gliocladium virens colonized both taproots and secondary roots after seed treatment with the fungal preparation. Colonization of taproots by G. virens increased over time, and decreased with root depth. Under field conditions, colonization of the taproots by G. virens occurred primarily in the upper 5 cm and declined sharply with depth. The percentage colonization of secondary roots by G. virens was extremely low. Gliocladium virens strains varied in ability to colonize cotton roots. The total colonization of taproots and secondary roots of cotton seedlings by Fusaria was reduced by seed treatment with biocontrol agents G. virens strains G-4 and G-6, and B. subtilis strains GBO3 and GBO7. The proportion of F. solani in the total Fusarium population was reduced by B. subtilis. Gliocladium virens did not affect the proportion of any individual Fusarium species in the total Fusarium population on cotton roots. Seed treatments with strains G-4 and G-6 of G. virens, strains GBO3 and GBO7 of B. subtilis, or several nonpathogenic isolates of Fusarium species suppressed, under greenhouse conditions, the incidence and severity of Fusarium wilt of cotton in soil infested with Fusarium oxysporum f. sp. vasinfectum and Meloidogyne incognita. Gliotoxin, produced by 'Q'-group strains of G. virens, is the antibiotic responsible for inhibiting F. o. vasinfectum in vitro. Seed treatments with G. virens or B. subtilis did not affect the reproduction of root-knot nematodes on cotton. |
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| Item Description: | Vita. "Major Subject: Plant Pathology". |
| Physical Description: | xiii, 99 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |