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ARS Home » Southeast Area » Tifton, Georgia » Crop Protection and Management Research » Research » Publications at this Location » Publication #340648
Title: Influence of root exudates and soil on attachment of Pasteuria penetrans to Meloidogyne arenaria

Author
item LIU, CHANG - University Of Georgia
item Timper, Patricia - Patty
item JI, PINGSHENG - University Of Georgia
item MEKETE, TESFAMARIAM - University Of Florida
item JOSEPH, SOUMI - University Of Florida

Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/5/2017
Publication Date: 9/25/2017
Citation: Liu, C., Timper, P., Ji, P., Mekete, T., Joseph, S. 2017. Influence of root exudates and soil on attachment of Pasteuria penetrans to Meloidogyne arenaria. Journal of Nematology. 49:304-310.

Interpretive Summary: Pasteuria penetrans is a bacterium that parasitizes root-knot nematodes (RKN). Spores of P. penetrans attach to the cuticle of RKN juveniles and subsequently sterilize infected females. When encumbered by large numbers of spores, juveniles are less mobile and their ability to infect roots is reduced. This study looked at different factors that influence spore attachment of P. penetrans to RKN. Incubating RKN juveniles with root exudates of eggplant reduced spore attachment compared to incubation with saline, suggesting the nematode surface coat was altered or the spore recognition sites on the nematode surface were blocked. Spore attachment was equally reduced following exposure to root exudates from both host and non-host plants for RKN, indicating that there is a common signal that affects spore attachment. Although plant hormones have been shown to influence the surface coat of nematodes, they did not affect spore attachment compared to saline. Root exudates reduced spore attachment more in sterilized soil than in natural soil. Sterilization may have eliminated microbes that consume root exudates, or altered the chemical components of the soil solution or root exudates. Root exudates had a greater decrease in spore attachment in sand than in clay. With better adsorbent ability, clay is likely to adsorb more components from root exudates that may have affected spore attachment. The results of this study demonstrate that root exudates can decrease attachment of P. penetrans spores to root-knot nematodes, indicating that when these nematodes enter the root zone their susceptibility to spore attachment may decrease.

Technical Abstract: Pasteuria penetrans is a parasite of root-knot nematodes (Meloidogyne spp.). Endospores of P. penetrans attach to the cuticle of second-stage juveniles (J2) and subsequently sterilize infected females. When encumbered by large numbers of spores, juveniles are less mobile and their ability to infect roots is reduced. This study looked at different factors that influence spore attachment of P. penetrans to M. arenaria. Incubating J2 with root exudates of eggplant (Solanum melongena) reduced spore attachment compared to incubation with phosphate-buffered saline (PBS), suggesting the nematode surface coat was altered or the spore recognition domains on the nematode surface were blocked. Spore attachment was equally reduced following exposure to root exudates from both host and non-host plants for M. arenaria, indicating that there is a common signal that affects spore attachment. Although phytohormones have been shown to influence the lipophilicity of the surface coat, auxins and kinetins did not affect spore attachment compared to PBS. Root exudates reduced spore attachment more in sterilized soil than in natural soil. Sterilization may have eliminated microbes that consume root exudates, or altered the chemical components of the soil solution or root exudates. Root exudates had a greater decrease in spore attachment in sand than in clay. With better adsorbent ability, clay is likely to adsorb more components from root exudates that may have affected spore attachment. The components of the root exudates could have also been modified by soil type. The results of this study demonstrate that root exudates can decrease attachment of P. penetrans endospores to root-knot nematodes, indicating that when these nematodes enter the root zone their susceptibility to spore attachment may decrease.