Influence of rhizosphere antagonists on suppression of cucumber wilt, increased cucumber growth and density fluctuation of Fusarium oxysporum f. sp. cucumerinum Owen
1988
Kim, H.K. | Jee, H.J. (Kyongsang National Univ., Chinju (Korea R.). Coll. of Agriculture)
When antagonistic microorganisms to Fusarium oxysporum f.sp. cucumerinum were introduced into natural field soil artificially infested by the pathogen, initial symptoms appeared late and progress of cucumber wilt was relatively slow. Disease severity and incidence were significantly reduced. In addition, cucumber growth in antagonist-treated plots was superior to that in untreated plot. Pseudomonas fluorescens and Trichoderma harzianum presented most predominant disease control effect over 50% compared to non-treated plots. There was no suppressive effect on disease by antagonists in steam sterilized soil, where all the plots were severely diseased and cucumber growth was remarkably retarded. Possible mechanism to explain such an observation are evidenced and discussed. Cucumber seedling growth was significantly promoted by antagonists being about 20-50% greater in natural field soil and steam sterilized soil. Increased cucumber growth was greater in field soil plots than in steam sterilized plots. Antagonists that revealed outstanding inhibition to F. oxysporum f. sp. cucumerinum also promoted cucumber growth remarkably. Antagonists, Serratia sp. and P. putida were successfully colonizing the cucumber rhizosphere over 1.1 x 10** (4) cfu/g soil until 21 days after inoculation while the population size was abruptly declined in non-rhizosphere soil 7 days after inoculation. Population densities of the pathogen, when introduced into natural field soil, increased tenfold in 7 days in all plots regardless of presence or absence of antagonists
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