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United States Department of Agriculture

Agricultural Research Service

Title: Understanding the molecular basis of the resistance of Phytophthora infestans to fungicides by functional genomics

Authors
item Champaco, Ethel
item Larkin, Robert
item DE Los Reyes, Benildo

Submitted to: Northeast Potato Technology Forum Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: March 4, 2012
Publication Date: March 7, 2012
Citation: Champaco, E., Larkin, R.P., De Los Reyes, B.G. 2012. Understanding the molecular basis of the resistance of Phytophthora infestans to fungicides by functional genomics. Northeast Potato Technology Forum Abstracts. p. 34.

Technical Abstract: Development of resistance to fungicides is a major concern in managing potato late blight disease caused by Phytophthora infestans. The problem is P. infestans is capable of sexual recombination contributing to increased strain variability and high adaptability that hastens the development of resistance to fungicides. Many of the fungicides currently being used do not have curative activity, so frequent applications are necessary, as often as every 3-5 days to protect against infections. The impact on the environment is therefore of great concern. Using a functional genomics approach, preliminary research was conducted to develop some insights on how P. infestans adapts to strong selection pressures imposed by constant fungicide application. Two isolates with subtle differences in Mefenoxam resistance were exposed to low and moderate concentrations of Mancozeb (Dithane 75DF Rainshield, 75% active ingredient) or Mefenoxam (97% active ingredient). A high titer cDNA library consisting of 1.3 x 107 primary clones was obtained and subsequently amplifed to achieve almost 5.0 x 1019 clones representing all the genes that are expressed by the two strains challenged with these fungicides. The constructed library is composed of lambda bacteriophage containing cloned cDNA inserts ranging in size from 500 to 1,000 bp. A total of 560 clones were randomly selected from both the primary and amplified secondary library. Plasmid DNA was prepared from each clone, digested with restriction enzymes EcoRI and XhoI, electrophoresed on an agarose gel and those plasmid prep showing insert sizes of >500 bp were selected for partial sequencing. Approximately 400 ESTs were obtained and putative gene identification and function were determined.

Last Modified: 11/28/2014
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