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United States Department of Agriculture

Agricultural Research Service

Research Project: INTEGRATED MANAGEMENT OF PLANT-PARASITIC NEMATODES IN COTTON AND PEANUT Title: Population dynamics of Dactylella oviparasitica and Heterodera schachtii: Toward a decision model for sugar beet planting

Authors
item Yang, J -
item Benecke, S -
item Jeske, D -
item Rocha, F -
item Smith-Becker, J -
item Timper, Patricia
item Becker, J -
item Borneman, J -

Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 30, 2012
Publication Date: September 15, 2012
Citation: Yang, J., Benecke, S., Jeske, D.R., Rocha, F., Smith-Becker, J., Timper, P., Becker, J.O., Borneman, J. 2012. Population dynamics of Dactylella oviparasitica and Heterodera schachtii: Toward a decision model for sugar beet planting. Journal of Nematology. 44:237-244.

Interpretive Summary: A series of investigations were performed to examine the population dynamics of the sugarbeet cyst nematode (SBCN) and the nematode-parasitic fungus Dactylella oviparasitica. After two nematode generations, the population densities of SBCN were measured in relation to various initial infestation densities of both the fungus and the nematode. In general, higher initial levels of the fungus were associated with lower final levels of SBCN. The study found that initial densities of the fungus were only able to predict the final densities of SBCN eggs and juveniles as well as fungal egg parasitism, while the initial densities of SBCN juveniles were able to predict all final population measurements of the nematode. We also showed that the densities of the fungus within cysts fluctuate greatly, with very little of the fungus found in cysts from field soil and large amounts of the fungus found in cysts isolated directly from root surfaces. Finally, phylogenetic analysis of rRNA genes suggested that D. oviparasitica belongs to a group of nematode-parasitic fungi with a wide geographical distribution. We believe that these findings will provide foundational data facilitating the development of more effective decision models for sugar beet planting.

Technical Abstract: A series of investigations were performed to examine the population dynamics of the sugarbeet cyst nematode, Heterodera schachtii, and the nematophagus fungus Dactylella oviparasitica. After two nematode generations, the population densities of H. schachtii were measured in relation to various initial infestation densities of both D. oviparasitica and H. schachtii. In general, higher initial levels of D. oviparasitica were associated with lower final levels of H. schachtii. Regression models showed that the initial densities of D. oviparasitica were only significant when predicting the final densities of H. schachtii J2 and eggs as well as fungal egg parasitism, while the initial densities of J2 were significant for all final H. schachtii population density measurements. We also showed that the densities of H. schachtii-associated D. oviparasitica fluctuate greatly, with rRNA gene numbers going from zero in most field-soil-collected cysts to an average of 4.24 x 108 in cysts isolated directly from root surfaces. Finally, phylogenetic analysis of rRNA genes suggested that D. oviparasitica belongs to a clade of nematophagous fungi with a wide geographical distribution. We suggest that these findings will provide foundational data facilitating the development of more effective decision models for sugar beet planting.

Last Modified: 10/20/2014
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