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Title: Studies on the use of Xenorhabdus spp. for the management of root-knot nematode (Meloidogyne javanica) on tomato
Author: Tabil, Magnus Amos
ISNI:       0000 0001 3495 3641
Awarding Body: University of Reading
Current Institution: University of Reading
Date of Award: 2007
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The effect of cells and toxins of Xenorhabdus spp. as biological .control on root-knot nematode (Meloidogyne javanica) was investigated. The mutualist b~cteria were obtained from two entomopathogenic nematodes, Steinemema abbasi and S. riobrave originating from the United Arab Emirates and were identified to the genus level using molecular techniques and the partial 16S rRNA gene sequences were deposited with the GENBANK. The bacteria were given Accession numbers as 00186672 for Xenorhabdus sp. RUAE (fro':l Steinemema abbasl) and 00186671, 00186674 and 00186673 for Xenorhabdus sp. 119, Xenorhabdus sp.120 and Xenorhabdus sp.124 from and S. riobrave. 00186672 was closely related to X. japonica and X. nematophila while the other three were found to be same species having 100% gene sequence homology. Cells and toxins of X. bovienii, X. nematophila and Xenorhabdus sp. RUAE (00186672) proved nematoxic to M. javanica. Higher concentrations of cells and toxins were more effective in immobilisation of juveniles and suppression of hatching of eggs than the lower concentrations. At 25°C, X. nematophila inhibited more egg hatch than ?. bovienii. The four newly isolated Xenorhabdus spp. equally inhibited egg' hatch and immobilised J2. At concentration of 2x1 07 cells/ml, X. nematophila, Xenorhabdus sp. 119 (00186671) and Xenorhabdus sp.120 (00186674) completely prevented egg hatch. Cell suspensions of all the Xenorhabdus spp. used caused more than 80-90% immobilisation of juveniles. On phytotoxicity, 30min exposure of roots of tomato seedlings recorded the highest survival at concentrations of 2x107 and 4x107cells/ml. X. nematophila and Xenorhabdus sp. RUAE (00186672) when stored in compost soil for 2 months caused over 60% mortality of larvae of Gallaria mellonella. When the same bacteria were stored in sealed bottles either in a fridge (at 5°C) or on the laboratory bench for one year recorded over 60% immobilisation of juveniles of M. incognita. When used as a soil drench, all the bacteria reduced penetration of roots and production of eggs. Similar results were obtained when tomato plants were treated with bacteria as bare-root dip for 30 min. When the bacteria were applied as bare-root dip for the tomato seedlings and transplanted into soil naturally-infested with root-knot nematode, the suppression of penetration and egg formation was less effective.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available