Le, Thi Thu Huong: Activity of fungal and bacterial endophytes for the biological control of the root-knot nematode Meloidogyne graminicola in rice under oxic and anoxic soil conditions. - Bonn, 2010. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn.
Online-Ausgabe in bonndoc: https://nbn-resolving.org/urn:nbn:de:hbz:5N-21592
urn: https://nbn-resolving.org/urn:nbn:de:hbz:5N-21592,
author = {{Thi Thu Huong Le}},
title = {Activity of fungal and bacterial endophytes for the biological control of the root-knot nematode Meloidogyne graminicola in rice under oxic and anoxic soil conditions},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2010,
month = jun,

note = {Two endophytic Fusarium moniliforme isolates Fe1 and Fe14, an endophytic bacterium Bacillus megaterium Bm and a rhizosphere Trichoderma isolate T30 with known antagonistic activity toward the root-knot nematode Meloidogyne graminicola were studied for bio-enhancement of rice under glasshouse conditions.
The level of colonization of Fe1 and Fe14 in the rice root under oxic and anoxic soil environments was investigated. The fungi were inoculated twice to the rice seeds using seed treatment and soil drenching methods at a rate of 106 cfu/ seed and 105 cfu/ seedling respectively. Both Fe1 and Fe14 isolates colonized well in the rice roots under oxic and anoxic soil water regimes with colonization rate ranged between 50-89%. The fungi colonized all parts of the roots though the preferable zone was the root periphery. The level of colonization decreased over time, from 56% after 8 weeks to 27% after 12 weeks of incubation. Both isolates did not show consistent effect on the growth of rice.
The mechanisms of action of the endophytic F. moniliforme isolate Fe14 was studied intensively under glasshouse conditions. In these experiments, Fe14 was also inoculated twice by seed coating and soil drenching techniques. The fungus reduced nematode penetration into the rice root significantly by up to 55% compared to the control. In a split-root experimental design, the fungus showed induced systemic resistance in rice when one half of the root system was treated with fungal spores while the other half was inoculated with the root-knot nematode. Root exudates from fungal treated plants showed repellent effect toward M. graminicola in a plastic test chamber. Fe14 also altered nematode development expressing by significantly higher number of males in fungal treated plants. Furthermore, Fe14 reduced the number of females and number of eggs per female compared to those of the control treatment. In addition, Fe14 exhibited high level of biocontrol under anoxic soil conditions by reducing the total number of nematodes in the endorhiza significantly by 45%.
Influence of inoculation time and method on biocontrol efficacy of Fe14 was also evaluated. In the first test, the ability of Fe14 for early protection of M. graminicola was tested in comparison to other antagonistic fungi. Out of the five fungi tested, F. moniliforme Fe1 and Fe14, F. oxysporum Fo162, Fusarium F28 and Trichoderma T30, only Trichoderma T30 was able to reduce nematode infestation in rice seedlings when both nematode and fungi were inoculated at sowing. However, Fe14 remained its biocontrol activity against the rice root-knot nematode 10 weeks after fungal inoculation. The effectiveness of different inoculation methods of Fe14 was also investigated. Both seed treatment and soil drenching methods led to similarly significant reductions in nematode damage. Double inoculations of Fe14, one at sowing and the other one repeated three weeks later did not result in significantly higher biocontrol level compared to single inoculation at sowing.
To enhance biocontrol efficacy, Fe14 was combined with Trichoderma T30 and the endophytic bacterium B. megaterium Bm in various greenhouse experiments. The three antagonists were first tested for their compatibility in vitro. No clear mutual exclusive was observed in any pair tests. Dual application of Fe14 and T30 in vivo reduced nematode infestation significantly compared to the control but the difference between single and combined treatments was not significant. Similarly, when Fe14 was combined simultaneously or in a staggered time manner with T30 and Bm, galling severity caused by M. graminicola significantly reduced by 20-70% compared to the control. However, none of the combinations led to significantly higher level of biocontrol compared to single applications and thus, single treatments of each biocontrol agent was adequate.},

url = {http://hdl.handle.net/20.500.11811/4204}

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