Biological Control of Meloidogyne hapla Using an Antagonistic Bacterium

Abstract

We examined the efficacy of a bacterium for biocontrol of the root-knot nematode (RKN) Meloidogyne hapla in carrot (Daucus carota subsp. sativus) and tomato (Solanum lycopersicum). Among 542 bacterial isolates from various soils and plants, the highest nematode mortality was observed for treatments with isolate C1-7, which was identified as Bacillus cereus based on cultural and morphological characteristics, the Biolog program, and 16S rRNA sequencing analyses. The population density and the nematicidal activity of B. cereus C1-7 remained high until the end of culture in brain heart infusion broth, suggesting that it may have sustainable biocontrol potential. In pot experiments, the biocontrol efficacy of B. cereus C1-7 was high, showing complete inhibition of root gall or egg mass formation by RKN in carrot and tomato plants, and subsequently reducing RKN damage and suppressing nematode population growth, respectively. Light microscopy of RKN-infected carrot root tissues treated with C1-7 showed reduced formation of gall cells and fully developed giant cells, while extensive gall cells and fully mature giant cells with prominent cell wall ingrowths formed in the untreated control plants infected with RKNs. These histopathological characteristics may be the result of residual or systemic biocontrol activity of the bacterium, which may coincide with the biocontrol efficacies of nematodes in pots. These results suggest that B. cereus C1-7 can be used as a biocontrol agent for M. hapla.

Comparisons of Pathological Responses in Carrot to Root-knot Nematodes

“…It was known that M. hapla produces tiny galls, while M. incognita produces larger galls and more severe stunting, yellowing and wilting symptoms on a wide variety of vegetable crops including the carrot ( Sardanelli et al, 1983 ). It is also noticed in our previous studies that remarkably larger galls are formed in susceptible carrot lines infected with M. incognita ( Seo et al, 2014 ) than those infected with M. hapla ( Park et al, 2014 ). It has been experienced that the root-knot galls formed on carrots grown in Jeju province (open fields) were characteristically small as those formed by M. hapla in the present study (unpublished data, 2014).…”

“…Among them, the use of resistant cultivars for rotation is an ideal method of controlling the nematodes on carrot with no or little additional cost required for the nematode control ( Kinlock and Hinson, 1972 ; Rhoades, 1976 ). However, there is currently no cultivar available in Korea with high level of resistance to M. incognita and M. hapla , but only two studies were conducted in relation to the screening of Korean carrot lines against the infections of M. incognita ( Seo et al, 2014 ) and M. hapla ( Park et al, 2014 ).…”

“…A commercial carrot cultivar Shinheukjeon-5-chon (SHC) and a currently-developed hybrid line MJ 11-8 (F 1 ) and the crossing parental lines {MJ 11-8 (♀) and MJ 11-8 (♂)} developed in KC Carrot Breeding Institute, Korea, were used for the nematode inoculation. The root-knot nematodes M. incognita Race 1 and M. hapla were used as inocula as used in the other previous studies ( Park et al, 2014 ; Seo et al, 2014 ). Seeds of the carrot lines were germinated in vermiculite at 20°C for 1 week and then planted in 9 cm (diameter) × 8 cm (depth) plastic pots filled with 1:1 mixture of river sand and potting soil mixture sterilized at 121°C for 15 min.…”

Biological Control of Root-Knot Nematodes by Organic Acid-Producing Lactobacillus brevis WiKim0069 Isolated from Kimchi

“…The root-knot nematodes M. incognita , M. hapla , and M. arenaria were acquired from the Korea Research Institute of Chemical Technology (Republic of Korea), Seoul National University (Republic of Korea), and National Institute of Agricultural Science and Technology (Republic of Korea), respectively (Hwang et al, 2014; Kim et al, 2001; Park et al, 2014). …”

Biological Control of Meloidogyne incognita by Aspergillus niger F22 Producing Oxalic Acid

“…Meloidogyne hapla was isolated from root galls of ginseng cultivated in Jinan-gun, Jeon-buk, Korea [ 26 ]. Four-week-old tomato plants ( Solanum lycopersicum cv.…”