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SPECIAL SESSION: Plant Pathologists of the Future: Showcasing Graduate Student Presentation Winners from APS Division Meetings

Evidence of a trans-kingdom plant disease complex between a fungus and plant-parasitic nematodes
David Wheeler - Montana State University.

Verticillium wilt reduces yields in mint fields. Management of wilt is limited because Verticillium dahliae (Vd) survives in soil for over a decade, synergistically interacts with the root-lesion nematode Pratylenchus penetrans (Pp), infects a wide range of crops, and resistance is not available in most mint cultivars. Risk assessment tools are required to inform management decisions concerning field selection and soil fumigation before planting. The objective of this research was to develop a model to predict the occurrence of wilt in mint fields. Soil samples were collected from 96 study sites in 30 mint fields in Oregon and Washington. Vd and Pp were quantified with quantitative real-time PCR or counted, respectively, and wilted stems were subsequently quantified in fields. Parametric and kernel-based non-parametric models were fit to the data, compared, and cross-validated. Although the parametric model was not misspecified (Jn = 0.11, p = 0.07), the non-parametric model had a slightly greater multiple R2 (0.58 vs 0.53) and a lower predicted square error (3.5 vs. 25.7) than the parametric model. Both models identified estimates of Vd DNA, counts of Pp, mint cultivar, and crop age as predictors of wilt in mint fields. These models (i) revealed the quantitative aspects of the four-way interaction between wilt, two pathogens, host cultivar, and host age and (ii) provide a foundation on which predictive forecasting tools can be developed for mint growers.