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United States Department of Agriculture

Agricultural Research Service

Research Project: Disease Modeling and Genetic Approaches to Enhance Wheat and Grass Seed Crop Biosecurity

Location: Forage Seed and Cereal Research

2012 Annual Report

1a. Objectives (from AD-416):
Objective 1. Discover and test germplasm that has genetic resistance to principal or emerging diseases in forage seed and wheat production. Subobjective 1.A. Develop an approach for evaluation of orchardgrass germplasm for resistance to choke disease. Subobjective 1.B. Identify germplasm of Lolium with resistance to rust diseases. Subobjective 1.C. Identify germplasm and increase seed for wheat and barley lines with resistance to stem rust Ug99. Subobjective 1.D. Identify genomic sequences in Brachypodium associated with non-host resistance to the wheat stem rust pathogen. Objective 2. Develop plant disease modeling tools to protect food supply and implement biosecurity strategies against rusts and other diseases of grass and wheat. Subobjective 2.A. Develop a model for timing of application of fungicides for control of ergot in Kentucky bluegrass. Subobjective 2.B. Determine the role of aphids in infection of orchardgrass by Epichloe typhina. Subobjective 2.C. Implement weather-based epidemiological model for stem rust of perennial ryegrass. Subobjective 2.D. Adapt ryegrass stem rust models to wheat stem rust.

1b. Approach (from AD-416):
Genetic resistance to stem rust will be investigated in cereal crops by selection, breeding and field evaluations, and in grasses by genetic mapping, quantitative trait loci analysis and transcriptome analysis. Molecular markers for stem rust resistance in Lolium will be chosen and validated. Genetic sequences associated with initial response of Brachypodium to the stem rust pathogen will be determined. Greenhouse and field experiments will be used to detect genetic resistance to the choke pathogen in grasses, and to determine whether aphids play a role in the infection process for this pathogen. An epidemic model for stem rust in grasses will be validated and expanded to include overwintering phenomena, and the grass stem rust model will be applied to wheat stem rust by experimental determination of critical parameters in greenhouse and field tests. Field experiments will be used to create a predictive model for infection by the ergot pathogen.

3. Progress Report:
This project replaces research project 5358-22000-035-00D (normal progression) and was initiated in April of 2012. It has been operational for less than six months and progress is proportional to this partial-year time period. Objectives 1A, 1B, 2A, 2B, 2C and 2D follow from research completed in the previous 5-year project period. Objectives 1C and 1D represent research areas new to the current project. Progress for Objective 1 (disease resistance) includes testing and resistance selection of perennial ryegrass plants from a resistant-by-susceptible cross to obtain stem rust- and crown rust- resistant parent plants for the next generation of crosses. Work by university cooperators to make selections within UG99-resistant barley lines, and to construct a database for UG99 nursery wheats, has been initiated and progress is described in a subsequent paragraph. For the genetic analysis of stem rust resistance in Brachypodium, inbred lines of this grass with the desired reaction phenotypes to 3 different genetic forms of the pathogen have been chosen based on inoculation experiments, and experimental protocols have been tested and finalized for producing plant tissue responding to challenge by these pathogens. Photomicrographs of early-stage infection processes have been made. For Objective 2 (disease modeling), the model for overwinter behavior and survival of stem rust on ryegrass has been completed, and coding to a computer language has begun. Epidemiological experiments with wheat stem rust (latent period and infection efficiency) are partially completed.

4. Accomplishments

Last Modified: 06/28/2017
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