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.
The first milestone was to determine in field trials during 2009 to 2011 at the University of Missouri the percent seed infected by Phomopsis spp. among 12 MG III, 12 MG IV, and 12 MG V plant introductions. Seeds from all plots were evaluated for visual appearance, percent germination, and percent seed infected by Phomopsis spp. The ARS scienstists completed these trials and have reached this milestone.
One second milestone was to determine the effect of infurrow and foliar applications of the fungicide Quadris, foliar application of the herbicide Cobra, and select plant introductions on percent of seed infected with Phomopsis species in field trials during 2009 and 2010 and then submit the results for publication. We reached this milestone since the manuscript which does acknowledge support from United Soybean Board was submitted to Plant Disease for publication, and was accepted with revisions required. The revised version was submitted in February 2012, and it has been accepted for publication during 2012.
Management options for Phomopsis seed decay are very limited. Our objective was to determine the effect of infurrow and foliar applications of the fungicide Quadris, foliar application of the herbicide Cobra, and select plant introductions on percent of seed infected with Phomopsis species in field trials during 2009 and 2010. The results from field trials at the University of Missouri during 2009 and 2010 show that the fungicide and herbicide treatments did not affect the percent of seed infected with Phomopsis spp. and there were no differences in percent of seed infected with Phomopsis spp. among the accessions. Planting resistant soybean varieties is still the only reliable management option for phomopsis seed decay (PSD).