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Molecular Variation of the Northern Corn Leaf Blight Pathogen (Exserohilum turcicum) Population in Ontario (Preliminary).

Shoukouhi, P., Jindal, K., Reid, L.M., Woldermariam, T., Barasubiye, T., Dadej, K., Tenuta, A., Liu, M. 2017. Molecular Variation of the Northern Corn Leaf Blight Pathogen (Exserohilum turcicum) Population in Ontario (Preliminary). 70th Northeast Corn Improvement Conference, Ottawa, ON, Feb 21-22, 2017. Oral presentation.

Abstract

In the last 15 years, Northern Corn Leaf Blight has increasingly become problematic in corn production in Ontario. The breakdown of resistant genes indicates likely changes of the genetic structures in the pathogen population. Molecular techniques, i.e. RAPD, AFLP and isozyme, have been used to explore the genetic diversity of Exserohium turcicum populations in multiple countries i.e. China, Europe, Israel, Mexico and USA, but not yet in Canada. Haasbroek and colleagues (2014) developed 13 microsatellite markers to characterize E. turcicum isolates from South Africa with some success. We evaluated these markers with the 48 fungal isolates collected from Ontario 2014 and 2015 corn crops. Eight markers revealed polymorphisms for the samples tested. The number of alleles and the gene diversity range from 2 – 9, and 0.08 – 0.77 respectively. Although these markers cannot distinguish each individual race, they divided the races into two clusters: cluster 1 included the races that have overcome one to two R genes; cluster 2 two to four R genes, in a neighbor-joining tree. The subdivision was supported by the sub-population (K value) estimation using a model-based Bayesian clustering method (STRUCTURE 2.3.4). Analysis of Molecular Variation (AMOVA) test showed that the differentiation of these two populations is statistically significant, and population 1 has more alleles and higher gene diversity, likely representing more ancestral population, while population 2 is more derived.

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