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United States Department of Agriculture

Agricultural Research Service

Research Project: ENHANCING RESISTANCE TO ROOT ROT PATHOGENS OF SOYBEAN
2008 Annual Report


1a.Objectives (from AD-416)
Objective 1: Identify predominant races of Phytophthora sojae and assess the effectiveness of soybean resistance genes for incorporation into improved germplasm. Objective 2: Determine variability in virulence patterns of new and established Phytophthora sojae races. Objective 3: Establish and maintain isolates of Phytophthora sojae races as a resource for soybean germplasm enhancement and race identification of new field isolates. Objective 4: Determine the influence of crop management practices on soybean root diseases.


1b.Approach (from AD-416)
Use standard pathological techniques to determine virulence and frequency of Phytophthora sojae races; cooperate with other soybean researchers to determine predominent P. sojae races in the North Central region, and utilize established tillage and rotation plots with a history of Phytophthora root rot and/or sudden death syndrome to enhance development of disease control strategies as they relate to crop management practices.


3.Progress Report
Evaluation of soybean germplasm and pathogens to minimize disease losses: Studies established in previous years were continued in FY08 to verify and update the frequency of dominant races of Phytophthora sojae in soybean production fields. This information is needed to document changes in the pathogen and to develop control strategies. Management and culture of the P. sojae germplasm collection were continued. The Lead Scientist continued to identify and provide selected P. sojae races for germplasm enhancement in addition to coordinating the Uniform Soybean Tests for Northern States and Canada. Ongoing collaborative research with breeders at Purdue University and Virginia State University were continued and three germplasm lines were approved for release. Soybean lines ‘CL0J173-6-2’ and ‘CL0J173-6-8’ are conventional soybean cultivars with improved yield and disease resistant characteristics. The jointly developed 'vegetable' soybean line ‘Owens’ also has excellent mature seed agronomic qualities as well as vegetable qualities and is resistant to a number of important fungal pathogens. Seed of ‘Owens’ can be used for several soy-food products. Studies documenting the role of Fusarium solani f. sp. glycines (=F. virguliforme) root infection and sudden death syndrome (SDS) yield losses in soybean with tillage (no-till vs. chisel tillage), crop rotation, and host resistance, were continued in FY08. The limited research reported to date has indicated SDS is more likely to occur in soybeans with minimum tillage than with conventional tillage and that crop rotation has little impact on SDS. Currently, Indiana data do not agree with this statement. Root colonization of soybean plants by F. virguliforme and SDS yield reductions were higher in tilled (conventional plow and chisel) plots than in the no-till plots. Early appearance of foliage symptoms and root infection results also indicated that soybeans with continuous cropping or in a corn-soybean rotation are more likely to develop SDS than plants in corn-soybean-wheat rotations. This project contributes to the National Program 303 Plant Diseases mission to reduce crop losses resulting from diseases by defining the genetic, physiological, and biochemical processes that operate in the host and pathogen during disease development, determining influence of crop production practices on disease vulnerability, determining critical processes in pathogenesis that can be interrupted or prevented, and by identifying and manipulating new and existing sources of resistance to root diseases of soybean. Although bridging slightly into a couple of other components, the project makes primary contributions in Component 4 - Pathogen Biology, Genetics, Population Biology, Spread and Relationship with Hosts and Vectors. The project also contributes to the National Program 301 mission: Plant, microbial, and insect germplasm conservation and development. Germplasm enhancement relative to disease resistance is actively addressed by ongoing cooperative research with breeders and by the coordination of the USDA Uniform Soybean Tests for the Northern Region.


4.Accomplishments
1. Phytophthora resistance identified in soybean germplasm with high potential for soybean rust resistance. Multiple disease resistance is an important component of production agriculture; major challenges include resistance to Phytophthora root rot caused by evolving Phytophthora sojae races and the recently introduced invasive Asian soybean rust caused by Phakopsora pachyrhizi. The diseases caused by these two pathogens pose major threats to soybean production and profitability for U.S. soybean growers. Resistance to P. sojae was identified in soybean lines evaluated for Asian soybean rust at the University of Georgia in 2005 and 2006. Several of the soybean lines identified with Phytophthora resistance were among the elite rust resistant germplasm identified by the Georgia researchers in 2006. These Phytophthora resistance data are directly applicable to breeding programs focused on maintaining resistance as it impacts sustainability. This accomplishment contributes to the National Program 303 Plant Disease mission and is aligned with Component 2: Pathogen Biology, Genetics, Population Biology, Spread and Relationship with Hosts and Vectors and Performance Measure 3.2.5: Provide fundamental and applied scientific information and technology to protect agriculturally important plants from pests and diseases. The studies relate directly to the Plant Diseases mission to reduce crop losses resulting from diseases by identifying and manipulating new and existing sources of resistance to diseases of soybean. The awareness of Rps gene resistance in soybean germplasm with potential for rust resistance will be useful to public and private soybean breeders for the development of cultivars that will improve resistance and minimize yield losses.


5.Significant Activities that Support Special Target Populations
None.


6.Technology Transfer

Number of Non-Peer Reviewed Presentations and Proceedings1

Review Publications
Mebrahtu, T., Devine, T.E., Donald, P.A., Abney, T.S. 2007. Registration of owens vegetable soybean cultivar. Journal of Plant Registrations. 1(2):95-96.

Leroy, A.R., Abney, T.S. 2007. Registration of 'CL0J173-6-2' and 'CL0J173-6-8' Soybeans. Journal of Plant Registrations. 1(2):98-99.

Last Modified: 10/20/2014
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