Antagonistic potential of an Egyptian entomopathogenic nematode, compost and two native endophytic bacteria isolates against the root-knot nematode (Meloidogyne incognita) infecting potato under field conditions

Abstract

Abstract Background The root-knot nematode, Meloidogyne spp., are one of the most dominant and dangerous group of pests. The deformations and discolorations make tubers unmarketable and/or of less quality. Therefore, management of Meloidogyne spp. becomes an obligatory challenge that warrants intervention. Biological control agents are the best alternative tools for controlling plant-parasitic nematodes that comply with the requirements of the development of the green agriculture and that reduce the reliance on these harmful chemicals. Therefore, this study aimed to evaluate the effectiveness of compost singly, and in combinations with the bio-agents Heterorhabditis bacteriophora, and two bacterial isolates Nem 212 and Nem 213 against the root-knot nematode Meloidogyne incognita infecting potato plants under field conditions. Results Among 15 bacterial isolates (Nem205-Nem219) obtained from the rhizosphere of tomato and eggplant from Giza, Egypt, the two isolates (Nem 212 and Nem 213) were molecularly characterized based on the partial 16S rDNA sequencing analysis. These two bacterial isolates were deposited in the GenBank as Bacillus cereus Nem 212 and B. cereus Nem 213 and were tested against M. incognita J2s in vitro. Results showed that the cell filtrates of B. cereus Nem 212 and B. cereus Nem 213 gave the highest percentage of M. incognita J2s mortality (100%), after 48 h of the in vitro application. Moreover, all the applied treatments significantly suppressed the reproductive of M. incognita on potato plants and enhanced the potato crop yield under the field conditions. Compost enriched with B. cereus Nem 212 cell suspension was the most effective treatment. The combination between the bacterial cell suspension and the compost offered an increase in the disease curing and the potato plant growth and yield production, compared to the treatment with compost alone. The entomopathogenic nematode, Heterorhabditis bacteriophora, was relatively less effective in controlling M. incognita on potato, compared to B. cereus Nem 212 and/or B. cereus Nem 213 treatments. However, when compost was enriched with H. bacteriophora, it increased its capability to control the nematodes. Conclusions This study provides insights into the practical usage of EPNs H. bacteriophora, and the endophytic bacteria (B. cereus Nem 212 or B. cereus Nem 213) as biocontrol agents against M. incognita on potato plants. The application of compost enriched with the bacterial cell suspensions of either B. cereus Nem 212 or B. cereus Nem 213 and H. bacteriophora within Galleria mellonella cadaver proved efficient control of M. incognita infecting potato plants and improved the growth and yield of potato plants under field conditions.