Location: Horticultural Crops ResearchTitle: Developmental dynamics of Globodera ellingtonae in field-grown potato
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/15/2017
Publication Date: 7/1/2017
Citation: Phillips, W.S., Kitner, M.L., Zasada, I.A. 2017. Developmental dynamics of Globodera ellingtonae in field-grown potato. Plant Disease. 101(7):1182-1187. doi: 10.1094/PDIS-10-16-1439-RE.
Interpretive Summary: The potato cyst nematodes (PCN) Globodera rostochiensis and G. pallida occur worldwide and can cause over 80% yield loss of potato. Both of these nematodes are regulated pests in the U.S. Recently, a very similar nematode to PCN, G. ellingtonae was found in Oregon and Idaho. Little information exists regarding the developmental biology of this nematode. To address this question, field experiments were conducted and the development of G. ellingtonae on potato was monitored. It was found that this nematode invades the roots of potato very rapidly and the amount of time required for the nematode to complete a generation occurred after approximately 800 degree days above 6°C. Additionally, it was observed that there was a 50% reduction in the number of eggs of this nematode in soil not planted to potato. These results are significant because they provide the first report on the development of G. ellingtonae in a field environment. This research will be used by scientists and regulators to make decisions regarding the regulation of this nematode in the U.S.
Technical Abstract: Globodera ellingtonae is a recently described nematode parasite of potato, which is closely related to the economically-significant potato cyst nematodes, G. rostochiensis and G. pallida. Because of the close relationship of G. ellingtonae to the potato cyst nematodes, a greater understanding of its biology is critical. Three years of field research was conducted in Oregon exploring the hatching and developmental dynamics of G. ellingtonae in potato. In two trials, potato was inoculated with G. ellingtonae cysts and soil and root samples were collected weekly. Life stages (second-stage juvenile (J2) in soil and roots; third-stage juveniles (J3) and fourth-stage (J4) females and males in roots; males and females/cysts in soil; and egg number and developmental state) were quantified. In two additional trials, we performed weekly counts of eggs/cyst from packages containing high cyst density soil that were buried under potato or in bare soil at the time of planting. Second-stage juveniles of G. ellingtonae were found in soil 0 to 49 DAP, and occurrence appeared to be related to precipitation, with peak densities of J2 appearing after precipitation events. Two peaks of J2 invasion of roots were observed. Normalizing across year using accumulated developmental degree days above 6°C (DD6), the first adult females were observed at 387 and 449 DD6 in 2013 and 2014, respectively. The next generation of eggs was first observed from 675 to 854 DD6 and 50% egg development (containing a vermiform juvenile) occurred at approximately 920 DD6. A second J2 hatch was observed in both years at 927 to 1,073 DD6. Across years, a significant reduction in eggs/cysts under potato (> 50%) was observed 35 DAP, and at 63 DAP eggs/cyst were reduced by 76 to 96% compared to initial egg/cyst densities. In bare soil, the maximum reduction in densities of eggs/cyst ranged from 55 to 73%. These data provide optimal time frames for management practices designed to reduce nematode population densities, such as the application of nematicides or termination of trap crops.