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Fusarium wilt of radish (Raphanus sativus L.) is caused by the Fusarium oxysporum f. sp. raphani (FOR) which mainly attacks Raphanus spp. The pathogen is a soil-borne and forms chlamydospores io infected plant residues in soil. Infected pathogen colonizes the vascular tissue, leading to necrosis of the vascular tissue. Growth promoting beneficial organisms such as Pseudomonas fluorescens WCS374 (strain WCS374), P. putida RE10 (strain RE10) and Pseudomonas sp. EN415 (strain EN415) were used for microorganisms-mediated induction of systemic resistance in radish against Fusarium wilt. In this bioassy, the pathogens and were treated into soil separately or concurrently, and mixed the bacteria with the different level of combination. Significant suppression of the disease by bacterial treatments was gravy observed in pot bioassy. The disease incidence of the control recorded 46.5 % in the internal observation and 21.1 % in the external observation, respectively. The disease incidence of P. putida RE10 recorded 12.2% in the internal observation and 7.8% in the external observation, respectively. However, the disease incidence of P. fluorescens WCS374 which was proved to be highly suppressive to Fusarium wilt indicated 45.6% in the internal observation and 27.896 in the external observation, respectively. The disease incidence of P. putida RE10 mixed with P. fluorescens WCS374 or Pseudomonas sp. EN415 was in the range of 10.0-22.1 %. On the other band, the disease incidence of P. putida RE10 mixed with Pseudomonas sp. EN415 was in the range of 7.8-20.2%. The colonization by FOR was observed in the range of 2.4-5.1×10³/g on the root surface and 0.7-1.3 × 10³/g in the soil, but the numbers were not statistically different. As compared with 3.8×10³/g root of the control, the colonization of infested ROR indicated 2.9×10³/g root in separate treatments of P. putida RE10, and less than 3.8×10³/g root of the control. Also, the colonization of FOR recorded 5.1×10³/g root in mixed treatments of 3 bacterial strains such as P. putida RE10, P. fluorescens WCS374 and Pseudomonas sp. EN415. The colonization of FOR in soil was less than that of FOR in root part. Based on soil or root part, the colonization of ROR didn´t indicate a significant difference. The colonization of introduced 3 fluorescent pseudomonas was observed in the range of 2.3-4.0×10^7/g in the root surface and 0.9-1.8×10^7/g in soil, but the bacterial densities were significant different. When growth promoting organisms were introduced into the soil, the population of Pseudomonas sp. in the root part treated with P. putida RE10 was similar in number to the control and recorded the low numerical value as compared with any other treatments. The population density of Pseudomonas sp. in the treatment of P. putida RE10 indicated signifiant differences in the root part, but didn´t mow significant differences in soil. The population densities of infested FOR and introduced bacteria on the root were high in contrast to those of soil P. putida RE10 and Pseudomonas sp. EN415 used in this experiment appeared to induce the resistance of the host against Fusarium wilt.
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