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United States Department of Agriculture

Agricultural Research Service

Research Project: Screening Germplasm and Breeding for Resistance to Phomopsis Seed Decay of Soybean: Phase II Research

Location: Crop Genetics Research Unit

2013 Annual Report


1a.Objectives (from AD-416):
1. Develop breeding/mapping populations and select high-yield resistant breeding lines from the new sources of resistance identified in the first phase of this project. 2. Determine the genetics of resistance of these new sources of resistance and develop molecular markers for these traits. 3. Determine pathogen diversity with emphasis on how this affects the expression of resistance to Phomopisis Seed Decay (PSD) in soybean.


1b.Approach (from AD-416):
Field screening and laboratory assays will be conducted to determine:.
1)The resistance of soybean lines to Phomopisis Seed Decay (PSD); and.
2)The genetic and pathogenic diversity of PSD isolates collected and purified from different genotypes of soybean in different geographic origins.


3.Progress Report:

During this reporting period, data were analyzed from the 2012 field trails, in which 42 soybean lines (14 from each of three maturity groups MGIII, MGIV, and MGV) tested for resistance to Phomopsis seed decay (PSD) were planted in Kibler, Arkansas, (May 15, 2012) and Stoneville, Mississippi, (April 25, 2012). Based on the seed assay data from 2009 to 2012, 10 soybean Phomopsis seed decay (PSD) - resistant germplasm lines were identified. This year, those 10 resistant lines along with six susceptible lines were planted in Stoneville, Mississippi, on May 30, 2013, and were also planted in Kibler, Arkansas, on June 7. In each location, three field experiments (for maturity groups III, IV and V) were planted with four replications in a split-plot design in which the inoculation treatments (inoculated or non-inoculated) are the main units and soybean lines within each maturity group are the sub-unit. Two harvest times, at the R8 and the R8+2weeks stages (normal vs. delayed), will serve as repeated measures. The inoculated plots will be sprayed with Phomopsis spores at the R5 to R6 growth stage. There are 256 plots planted in each location. Overhead irrigation will be used to increase seed infection.

Isolates of Phomopsis (P.) longicolla were collected from seed harvested in past years in different states, and from lower stems of soybean plants grown in two fields in Arkansas and one field in Mississippi. Stem sections were collected from 100 locations in each field using a 20 X 20 m grid. Hundreds of isolates have thus far been collected. Efforts have been made to purify and single-spore those isolates. Selected isolates have been sequenced at internal transcribed spacer (ITS) region to confirm the pathogen identity. Identification of simple sequence repeat (SSR) markers based on the draft genome sequence of a P. longicolla from Mississippi is in progress.

For breeding and genetics purposes, the following plant populations are being advanced in Fayetteville, AR, for breeding/mapping purposes: F4 generation: 5002T x PI 417479, 5002T x PI 417050, and R03-984 x PI 417050. F3 generation: R07-R07-10244 x PI 424324B, R04-1268RR x PI 594858A, and R07-10231 x PI 235335. F2 Generation: PI 567635 x R01-976. F1 generation: PI 506647 x R05-3239, PI 567381B x Osage, and PI 567635 x UA 5612.

In addition, 41 new lines were selected from sudden death syndrone crosses (12 from 5002T x PI 417050, 12 from 5002T x PI 417479, and 16 from R03-984 x PI 417050). These lines are being evaluated for yield and PSD in Stuttgart, AR.

In Illinois, hand pollinations were made in the greenhouse to cross elite Midwestern lines with the PSD-resistant accessions PI 209908, PI 279088, and PI 360841. Although only a low percentage of those were successful, a few pods with putative F1 seeds have been found. Additional crosses will be made in the field in Urbana this summer. PSD-resistant accessions from maturity groups (MGs) II through IV have been planted outdoors, and PIs from higher MGs have been or will soon be planted in the greenhouse for this purpose. Putative F1 seeds that should have PSD resistance will be planted to the extent that this is possible.


Last Modified: 7/28/2014
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