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TECHNICAL SESSION: Epidemic analysis

Wheat blast dynamics within the plant canopy: A spatio-temporal analysis
Carlos Cecilio Gongora-Canul - Purdue University. Barbara Valent- Kansas State University, Laurence Madden- The Ohio State University, Pierce Paul- The Ohio State University, Jorge David Salgado- The Ohio State University, Christian Cruz- Purdue University

Understanding the spatio-temporal dynamics of wheat blast (WB), a devastating disease caused by the Triticum pathotype of Magnaporthe oryzae (MoT), will provide information useful for developing effective WB management strategies. Field experiments were conducted in 2014 at two locations in Bolivia to study the vertical spread of MoT and WB within the canopy of susceptible cultivar Arex, influenced by in-field crop residue as a source of inoculum. WB severity and MoT spore density were quantified following systematic assessments and sampling on leaves and spike, and negative exponential models were fit to the data to quantify disease gradient. The models showed a significant inverse vertical gradient of WB severity and spore density (P <0.05) from lower leaves up to the spike, using data collected at seven sampling dates after emergence. Repeated measures analyses showed significant differences in severity and spore density among plant organs at all seven sampling dates (P < 0.001). The effect of crop residue on severity and spore density was statistically significant in the lower canopy but not in the middle or upper canopy. Correlations between leaf layers in the canopy at a given sampling date and between sampling dates within same leaf layers were moderate to strong for both severity and spore density. These results provide invaluable insights into the spread of MoT inoculum and WB from leaves to spikes within the canopy, and the significance of auto-infection at the canopy level for wheat blast development.