2011 Annual Report
1a.Objectives (from AD-416)
Screen untaggeed germplasm lines for resistance to Phomopsis seed decay (PSD) of soybeans. Breed high-yielding resistant cultivars and germplasm lines for North Central and southern U.S. soybean production regions by incorporating new resistant genes and alleles. Develop new and rapid screening tools that are correlated with the field screening method for measurement of plant resistance.
1b.Approach (from AD-416)
Use field and laboratory approaches to identify sources of Phomopsis resistance.
During the first year of this project, 123 selected soybean germplasm lines collected from 28 countries, and breeding lines and cultivars from Southern U.S. will be screened in the fields of three states (Arkansas, Mississippi, and Missouri). Visual scoring and seed assay in laboratories on the incidence of the PSD pathogen will be performed. The top 10-15 resistant lines will be selected for the second year field trials with replicated inoculation and non-inoculation tests using local isolates from each state. Winter nursery facilities in Argentina and Costa Rica contracted by the University of Arkansas will be available to the team to speed up the process of generation advances. Mapping populations will be developed and molecular markers will be identified for use in marker-assisted selection.
Field trials have been conducted to test 42 soybean lines selected from the initial screening of 135 lines in three states. During this reporting period, field tests of 42 selected soybean lines (14 from each of three maturity groups: MGIII, MGIV, and MGV) for resistance to Phomopsis seed decay (PSD) were conducted in Arkansas, Mississippi, and Missouri. Those lines were selected based on the seed assay data from 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 with four replications at three locations: Kibler, AR (planted on June 8, 2011); Stoneville, MS (planted on May 20, 2011); and Portageville, MO (planted on May 18, 2011). Inoculation and non-inoculation were the main plots, and the maturity groups were the subplots, and lines in each maturity group were randomized with four replications for each inoculation treatment. Data of seed assays from 2010 experiments in three states have been collected and analyzed. Due to dry weather during seed maturation, seed infection by Phomopsis (P.) longicolla in 2010 was lower than that in 2009, but differences in seed infection by P. longicolla occurred among soybean lines.
Breeding for resistance to Phomopsis seed decay of soybean. In an effort to breed for PSD resistance, we 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 had good seed quality and PSD response and were evaluated for adaptation and yield in 2010. They showed early maturity, excellent seed quality, but relatively low yields and shattering problems. We discontinued these lines for yield testing but used them as parents for crossing in the next cycle of breeding. We constructed five (4 F4 and 1 F1) breeding populations to pyramid different PSD resistance genes from PI 91113, PI 360841, PI 417479, PI 235346, and PI 371611. We also developed seven (1 F3, 4 F2, and 2 F1) breeding populations to incorporate PSD resistance from different sources (PI 80837, PI 417479, PI 360841, PI 427050, PI 235346, and PI 235335) into high yielding MG IV-V cultivars/lines adapted to the mid-south. These breeding populations will be advanced in 2011. In addition, we developed a new mapping population (UA 4910 x PI 80837) to fine map the PSD resistance gene in PI 80837. This population was increased in Costa Rica in 2010 and is being advanced for recombinant inbred line development in 2011. ADODR used site visit, email and telephone conferences to monitor activities of the project.