Resistance to Meloidogyne incognita in cotton genotypes /
Root-knot nematodes (Meloidogyne incognita) are aggressive and wide spread pathogens of cotton (Gossypium hirsutum L.). To control the root-knot nematode disease, cotton genotypes with resistance to M. incognita have been released recently. To estimate the durability of the nematode resistance, aggr...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1999.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=731686121&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Root-knot nematodes (Meloidogyne incognita) are aggressive and wide spread pathogens of cotton (Gossypium hirsutum L.). To control the root-knot nematode disease, cotton genotypes with resistance to M. incognita have been released recently. To estimate the durability of the nematode resistance, aggressiveness of populations of M. incognita against the resistant cotton genotypes was measured. Nematode isolates were collected from 12 counties throughout the cotton production region of the southern high plains and several other counties Texas, and from several locations in other states. Root galling and nematode reproduction by these nematode isolates were consistently the lowest on M-3l5, the highest on DP90, and were intermediate and more variable on NemX and LA887. Analysis of variance indicated that the effects nematode isolates, cotton genotypes and the isolate-genotype interaction were significant (P < 0.05). Four isolates from a field in Texas were highly aggressive on the resistant cotton genotypes LA887 and NemX. Initial nematode population density was found to have a greater effect on yield of susceptible cultivar Paymaster HS26, than on yield of NemX and LA887 (P = 0.01). Increase in initial nematode population density (Pi) resulted greater reduction yield of susceptible cultivar than that of the resistant cultivars NemX and LA887 (10-15% greater at high Pi). The damage threshold parameter T for the resistant cultivars was not different from that for the susceptible cultivar HS26. The minimum yield parameter, however, was smaller for H526 than the resistant cultivars (P = 0.05). The results also showed that the resistant genotypes supported significantly less nematode growth and had significantly lower root galling than the susceptible genotype (P = 0.05). The inheritance of resistance to M. incognita in the cotton genotypes was determined. The results indicated the presence of one single recessive gene for resistance to M. incognita in the cotton cultivars NemX and LA887; and two major genes for resistance in one breeding line M-240, with one gene partially dominant and the other recessive. Most importantly, the results showed that the same single recessive resistance gene controls the resistance to N. incognita in NemX and LA887. |
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| Item Description: | Vita. "Major Subject: Plant Pathology". |
| Physical Description: | xv, 105 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 94-104). |