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United States Department of Agriculture

Agricultural Research Service

Research Project: BREEDING SELECTION AND MOLECULAR CHARACTERIZATION FOR IMPROVED SUGAR BEET GERMPLASM

Location: Sugarbeet and Bean Research

Title: Mating type idiomorphs distribution and their correlation to benzimidazole-resistance in Cercospora beticola from the Central High Plains Region, USA

Authors
item Obuya, James -
item Hanson, Linda
item Franc, Gary -

Submitted to: American Society of Sugar Beet Technologists
Publication Type: Abstract Only
Publication Acceptance Date: December 16, 2010
Publication Date: March 2, 2011
Citation: Obuya, J.O., Hanson, L.E., Franc, G.D. 2011. Mating type idiomorphs distribution and their correlation to benzimidazole-resistance in Cercospora beticola from the Central High Plains Region, USA. In: Proceedings of the American Society of Sugar Beet Technologists. 36th Biennial Meeting, March 2-5, 2011, Albuquerque, New Mexico. 2011 CDROM.

Technical Abstract: Cercospora leaf spot (CLS) of sugarbeet is caused by Cercospora beticola Sacc., and is one of the most destructive foliar diseases worldwide. Fungicides used for disease suppression include benzimidazoles. Resistance to benzimidazoles can develop quickly, and was first reported in C. beticola in 1973 from Greece. Despite reduced use, benzimidazole-resistance typically persists in the C. beticola population. We investigated the correlation between the distribution of mating types and benzimidazole-resistance in 179 C. beticola isolates recovered during prior CLS surveys. Representative isolates (173) were selected from 56 fields in 19 counties and four states in the Central High Plains (2004-2009), and six isolates were from Michigan (2008). Characterization revealed that 110 isolates were sensitive and 69 were resistant to benzimidazole. These isolates were then tested to determine the frequency of mating type idiomorphs by PCR amplification of mating type loci. Results revealed that c.a.80% of C. beticola isolates from the Central High Plains contained the MAT1-1 idiomorph in contrast to an equal distribution of mating type idiomorphs reported by a research group in Europe. Our results departed from the expected 1:1 ratio except for states that had low sample numbers, such as Wyoming (chi²=1.47, df=1) and Michigan (chi²=1, df=1, P=0.05), which had equal distributions of mating type idiomorphs. The latter observations are similar to that reported for C. beticola in the north central region of the United States. The unequal frequency of mating type idiomorphs indicated a potential lack of mating among the C. beticola population in sugarbeet growing areas of the Central High Plains region. Therefore, sexual recombination may not be occurring in a C. beticola population where benzimidazole resistance is known to persist.

Last Modified: 9/21/2014
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