Microbiological differences between limed and unlimed soils and their relationship with cavity spot disease of carrots (Daucus carota L.) caused by Pythium coloratum in Western Australia

Khaled A. El-Tarabily, Giles E.St J. Hardy, Krishnapillai Sivasithamparam, Ipek D. Kurtböke

Research output: Contribution to journalArticlepeer-review

47 Citations (Scopus)

Abstract

Application of lime (4000 kg ha-1) to a soil used for commercial carrot production (pH 6.9) significantly (p < 0.05) reduced the incidence of activity spot disease of carrots compared to unlimed soil (pH 5.1). It significantly (p < 0.01) increased soil microbial activity as measured by the hydrolysis of fluorescein diacetate and arginine ammonification. The application of lime resulted in a significant (p < 0.01) increase in the total numbers of colony forming units (cfu) of aerobic bacteria, fluorescent pseudomonads. Gram negative bacteria, actinomycetes and a significant (p < 0.01) decrease in the cfu of filamentous fungi and yeasts compared to unlimed soil. Liming also increased the cfu of non-streptomycete actinomycetes rarely reported in similar studies. These non-streptomycete actinomycetes were estimated and isolated using polyvalent Streptomyces phages and the dry heat technique to reduce the dominance of streptomycetes on isolation plates. The non-streptomycete actinomycetes isolated included species of Actinoplanes, Micromonospora, Streptoverticillium, Nocardia, Rhodococcus, Microbispora, Actinomadura, Dactylosporangium and Streptosporangium. The numbers of actinomycetes antagonistic to Pythium coloratum, a causal agent of cavity spot disease of carrots increased in soil amended with lime. Application of lime also reduced the isolation frequency of P. coloratum from asymptomatic carrot roots grown in soil artificially infested with the pathogen, 3, 4 and 5 weeks after sowing.

Original languageEnglish
Pages (from-to)279-290
Number of pages12
JournalPlant and Soil
Volume183
Issue number2
DOIs
Publication statusPublished - Jan 1 1996
Externally publishedYes

Keywords

  • Pythium coloratum
  • actinomycetes
  • antagonism
  • cavity spot
  • disease suppression
  • microbial activity

ASJC Scopus subject areas

  • Soil Science
  • Plant Science

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