2012 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.
During this reporting period, 42 soybean lines (14 from each of three maturity groups MGIII, MGIV, and MGV) that were tested in 2010 and 2011 for resistance to Phomopsis seed decay (PSD) were planted again in Kibler, Arkansas, (May 15, 2012), and Stoneville, Mississippi, (April 25, 2012). Those lines were selected based on the seed assay data on screening 135 lines in 2009, including 36 lines with low levels of PSD at two or more of the test sites and six checks from three maturity groups. Experiments were set up in a split-plot design. The inoculation (using a local Phomopsis isolate in each state at the R5 to R6 growth stage) and non-inoculation treatments are the main plots, maturity groups are the subplots, and lines in each maturity groups are randomized with four replications for each inoculation treatment. Overhead irrigation will be used to increase seed infection. A test comparing 13 foliar applied fungicides was planted on May 15 at the Vegetable Research Station, Kibler, Arkansas. The fungicides will be applied once at the R5 growth stage.
Isolates of homopsis longicolla have been collected from seed harvested in Stoneville, MS, in the past years, and from seedlings at the Southeast Research Station, Rohwer, AR. Additional isolates will be collected from northeast Arkansas for inoculation studies. Four isolates from Mississippi have been sequenced at the internal transcribed spacer (ITS) region to confirm the pathogen identity.
For breeding and genetics studies, the following plant populations are being advanced in Fayetteville, AR, for breeding/mapping purposes:
F3: 5002T x PI 417050, 5002T x PI 417479, R03-984 x PI 417050
F2: R07-10231 x PI 235335, R07-10244 x PI 424324B, R04-1268RR x PI 594858A
F1: PI 458130 x R05-3239, PI 506647 x UA 5612, PI 567635 x R01-976
The Phomopsis resistant parents are PI 417050, PI 417479, PI 235335, PI 424324B, PI 594858A, PI 458130, PI 506647, and PI 567635.
The following Phomopsis resistant PI’s also were planted in the crossing block for making new crosses this summer in Fayetteville, AR: PI 424324B, PI 458130, PI 506647, PI 567381B, PI 567635, PI 594858A, PI 567102B.
In Illinois’ location, PI 567381B plants grown in the greenhouse to be crossed with agronomically elite lines adapted to the midwest could not be used due to severe virus infections. Seeds of this accession, carefully chosen for their lack of virus symptoms, have been planted in the greenhouse for crossing this summer to generate agronomically competitive breeding lines with Phomopsis Seed Decay (PSD) resistance derived from PI 567381B.