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United States Department of Agriculture

Agricultural Research Service

Research Project: SCREENING GERMPLASM AND BREEDING FOR RESISTANCE TO PHOMOPSIS SEED DECAY IN SOYBEAN
2010 Annual Report


1a.Objectives (from AD-416)
(1) Screen soybean lines for resistance to Phomopsis Seed Decay (PSD). (2) Breed high-yielding resistant cultivars and germplasm lines for North Central and Southern U.S. soybean production regions by incorporating new resistance genes and alleles. (3) Develop new and rapid screening tools that are correlated with the field screening method for the measurement of plant resistance.


1b.Approach (from AD-416)
Phomopsis seed decay (PSD) of soybean is a major cause of poor quality and poor germination of soybean seeds in the United States, especially in the mid-southern U.S. This research will be focus on two sides of the disease equation:.
1)screening untapped (not yet tested for PSD resistance) 123 MG 3-5 germplasm lines collected from 28 countries, and.
2)breeding lines and cultivars from southern U.S. with resistance to PSD. This research will provide tools and potential new resistance genes to increase breeding efficiency for high-yield PSD resistant lines.


3.Progress Report

Seed infection by the causal agent of Phomopsis seed decay (PSD), Phomopsis (P.) longicolla, was determined in 135 plant introduction lines at the Vegetable Research Station in Kibler, AR. The lines were divided into three groups (maturity groups III, IV, and V) for testing, each group consisted of 45 lines planted in single row plots 3 m long and replicated four times. The test was planted on 5 June 2009 and was overhead irrigated as needed. Plots were not inoculated, but depended on natural inoculum for infection. Frequent rain during September and October delayed harvest. Plots were hand harvested and the seed was assessed for visual quality, germination, and infection. Seed infection was determined by incubating the seed on potato dextrose agar and identifying the fungi that grew out of the seed. The percent of seed with P. longicolla was recorded.

Visual quality, rated on a 1 to 5 scale, ranged from 2.3 to 4.7 for MG III, 2.8 to 5.0 for MG IV, and 2.8 to 4.5 for MG V. Germination ranged from 33 to 89% for MG III, 22 to 94% for MG IV, and 78 to 100% for MG V. Infection by P. longicolla ranged from 5.2 to 27.7% for MG III, 5.5 to 37.0% for MG IV, and 2.5 to 45% for MG V. Three reports on the results have been submitted for publication. Eight resistant lines and four susceptible lines were chosen for further evaluation in 2010.

In the effort of breeding for PSD resistance, the investigators has selected four advanced early-maturing lines with PSD resistance derived from PI 80837 and PI 360841 in 2009. These lines showed some levels of seed shattering in the field but good seed quality and PSD response. These lines will be evaluated for adaptation and yield in 2010. We have made five new cross combinations in attempt to incorporate PSD resistance from different sources (PI 80837, PI 417050, PI 417479, and PI 360841) into high yielding MG4-5 cultivars/lines adapted to the mid-south. In addition, the investigators constructed breeding populations to pyramid different PSD resistance genes from PI 91113, PI 360841, and PI 417479. This effort is on-going and will continue in 2010. The project was monitored through emails, telephone calls, and site visits.


Last Modified: 10/21/2014
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