Screening potatoes for resistance to late blight

Arier Lee
University of Auckland

C. M. Triggs
University of Auckland

J. A. D. Anderson
New Zealand Institute for Crop & Food Research Limited

World wide, potato (Solanum tuberosum L.) is considered one of the most important vegetable crops. Late blight caused by Phytophthora infestans is recognized as the most serious potato disease. A biennial field screening trial for resistance to late blight has been carried out at Pukekohe for over twenty years. Trials were laid out as latinised row and column designs in a single rectangular array of plots, indexed by rows and columns. In each trial disease severity based on the percentage of affected foliage was repeatedly assessed on a 1-9 ordinal scale from the first sign of infection in each trial and at 4 to 6 subsequent occasions.

Based on threshold model for ordinal responses, we developed a Bayesian nonlinear model which fits a logistic sigmoidal decay curve to the latent variable for repeated ordinal measurements and random effects arisen from latinised row and column design.

Session 3c, Environmetrics: 14:35 — 14:55, Room 445

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