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United States Department of Agriculture

Agricultural Research Service

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Research Project: Novel Strategies for Managing Blast Disease on Rice and Wheat

Location: Foreign Disease-Weed Science

Project Number: 8044-22000-041-10
Project Type: Reimbursable

Start Date: Jan 01, 2013
End Date: Dec 31, 2014

Objective:
1) Establish nursery plots in South America to screen U.S. wheat cultivars for resistance to wheat blast. 2) Characterize the pathogenic and genetic relationship among different Magnaporthe pathotypes. 3)Develop a diagnostic tool for differentiating the wheat blast pathogen from other Magnaporthe pathotypes. 4) Determine the potential survival rate of the pathogen as mycelium in infected host tissue in field soil as it relates to the overwintering potential of the pathogen. 5) Determine the effects of dew period and temperature on disease development, comparing an original 1988 Brazilian isolate with two isolates collected after 2010.

Approach:
1) In our BSL-3 containment greenhouses we have completed screening 270 winter wheat cultivars for resistance to 2 isolates of wheat blast and have begun testing spring wheat cultivars. Working with Kansas State University we will sellect cultivars which consistantly show less than 5% head infection for planting at nursery sites in Bolivia and Brazil. Selected cultivars will be tested in the field for at least 3 seasons. 2) We will obtain a collection of commonly occuring grass species prevelent in wheat fields as well as those listed as a host for Magnaporthe. In a replicated experiment grass species will be inoculated at both the 3-4 leaf stage and at flowering with pathotypes on Magnaporthe from Millet, Setaria, Rice, Wheat, Lolium and St. Augustine grass. Infection will be scored by leason type and density. The study will be conducted at 18, 24 and 28 C. 3) DNA will be extracted in the From the closely related Lolium and wheat blast pathotyes and DNA fingerprinting performed with the MGR583 and Pot2 markers (Farman 2002). We will perform genome sequencing of representative isolates from the predominant Mot/Mol lineages (5 from wheat and 5 from perennial/annual ryegrass – to be selected based on DNA fingerprints). The genome sequence information will be analyzed with the SNPsfinder program to identify suitable marker loci (~100, including the mating-type locus) capable of distinguishing among lineages/populations. Genotyping of up to 1,000 Lolium/Wheat isolates will then be performed using an amplicon-based, multiplexed/barcoded sequencing strategy on the GS FLX 454 Pyrosequencer in the University of Kentucky Advanced Genetic Technologies Center where Farman is director. 4) Utilizing growth chambers and programmable incubators in a BSL-3 laboratory in Ft. Detrick, we will layer plant material infected with a wheat blast isolate of M. oryzae (transformed with a plasmid imparting G418 antibiotic resistance) into containers of Maryland field soil. Replicated treatments will consist of 6 temperatures between -5 and 28°C. For each temperature, 3 soil moisture profiles will be tested.Infected plant debris will be sampled at 21 d intervals. Debris will be rinsed in sterile water and transferred to antibiotic-augmented oatmeal agar.for fungal recovery. The study will be repeated with two additional soil types. 5) Utilizing temperature controlled dew chambers in a BSL-3 laboratory, replicated studies will be conducted to characterize the relationship between dew period and temperature in the infection process. We will repeat this study to compare results using several recently acquired wheat blast isolates and an isolate originally collected in Parana, Brazil in 1988.

Last Modified: 10/22/2014
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