Potential of actinomycetes isolated from earthworm castings in controlling root-knot nematode Meloidogyne incognita
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Morphological and molecular analyses of 25 actinomycete isolates from five commercial earthworm castings in Thailand indicated that all isolates belonged to the genus Streptomyces. From primary screens of spore suspensions and culture filtrates of the isolates for in vitro effects on egg hatch and juvenile mortality of Meloidogyne incognita, 12 isolates that gave significant control of M. incognita were confirmed to reduce root penetration by M. incognita in a secondary screen using green bean. The 12 isolates were also evaluated for their efficiency against root-knot disease on chili in the greenhouse. Streptomyces sp. KPS-E004 reduced the egg hatch rate the most (by 55.8 % using spores, 62.4 % using culture filtrate) and increased the juvenile mortality rate the most (by 63.9 % with spores, 73.9 % with culture filtrate). In the secondary screen, all infective second-stage juveniles of M. incognita treated for 72 h with a spore suspension of KPS-E004 lost the ability to penetrate plant roots. Moreover, this strain had the highest root-knot disease control efficiency on chili (71.2 %). Thus, Streptomyces sp. KPS-E004 has potential as a biocontrol agent to control root-knot disease in organic and sustainable agricultural systems.
KeywordsActinomycetes Biological control Earthworm casting Meloidogyne incognita Root-knot nematode
The authors thank the Kasetsart University Research and Development Institute (KURDI) for financial support.
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