2011 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.
In 2010, we tested 12 maturity group (MG) III, 12 MG IV and 12 MG V plant introduction lines at the Vegetable Research Center, Kibler, AR. Results were compared to the reaction of these lines in 2009 at the same location. In addition, the 2010 test included the lines inoculated and uninoculated with Phomopsis (P.) longicolla, but these inoculations did not affect seed infection. Plants were inoculated in the evening by spraying spores into the canopy and irrigating the plots with overhead irrigation the next morning. With the MG III lines, the incidence of P.longicolla ranged from 9 to 37% in 2010 compared to 5 to 22% in 2009. The most resistant lines in both years were 416988 and 578486 with average infection levels of 15 and 9%, respectively. Eight lines that had relatively low ratings in 2009 (<13%) had relatively high ratings in 2010 (17 to 29%). With MG IV lines, the incidence of P. longicolla ranged from 1 to 39% compared to 7 to 33% in 2009. The most resistant lines in both years were 235346, 87074, and 355070 with infection levels of 16, 17, and 12%, respectively. Three lines had much higher infection in 2010 (26 to 39%) than 2009 (17-21%) and two lines had much higher incidences in 2009 (25 and 28%) than in 2010 (1 to 3%). With the MG IV lines, the incidence of P. longicolla ranged from 0 to 20% in 2010 compared to 7 to 27% in 2009. The most resistant plant introductions in both years were 506844, 471938, 476920, 507690, and 72902 with infection levels of 2, 1, 2, 4, and 0%, respectively. Six lines had much higher infection levels in 2009 (14 to 21%) than in 2010 (0 to 3%).
In addition to Phomopsis seed infection, plots were rated for natural infections by Cercospora (C.) kikuchii, the causal agent of purple seed stain. More C. kikuchii infection occurred in 2009 than in 2010 in MG III (15 vs 4%) and MG IV (13 vs 5%). Infection levels were similar for MG V (7 vs 4%). MG III lines that were resistant in both years were 417361, 437482, and 578486. The MG IV line that was resistant in both years was 80479. MG V lines that were resistant in both years were 381659, 407749, 476920, 72902, 407752, and 417098. All of the lines tested in 2010 are being tested again in 2011 and will include both P. longicolla inoculated and non-inoculated plots. ADODR used site visit, email and telephone conferences to monitor activities of the project.