Rhizosphere microbial community dynamics and the potential impact of organic matter amendment and Trichoderma ghanense Yoshim. Doi, Y. Abe and Sugiy. on the control of disease associated with soil sickness
2011
Bawagan-Banaay, C.G.O.
Aerobic rice is a water-saving technology where improved varieties are cultivated under non-flooded conditions. Initial observations indicate that continuous aerobic cultivation leads to soil-sickness. This thesis aims to determine the biotic factors contributing to soil-sickness and assess efficacy of organic matter (OM) amendments in alleviating this problem. The population dynamics and contribution of Pythium (particularly P. arrhenomanes) and Meloidogyne graminicola (RKN) to soil-sickness in aerobic rice were determined in the field and under controlled conditions. Pythium occurrence was correlated with stunting and root discoloration in seedlings while RKN was also correlated with both, but in older plants. Both pathogens have the potential to interact synergistically but may also be antagonistic with each other depending on the host. They are amenable to biological control using OM amendment through composting and application of Trichoderma ghanense CDO. Reduction of root galls and isolation frequency of Pythium with OM amendment were shown. One basis for disease control seems to be related to increased bacterial and fungal diversity. Under controlled conditions, CDO reduced the disease symptoms in P. arrhenomanes-infected seedlings. Potentially, CDO may control the disease through mycoparasitism, antibiosis, inhibitory metabolite production, and growth-promotion. CDO was also shown to induce systemic resistance in rice against blast and sheath blight pathogens.
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