ARS | Publication request: Identification of soybean accessions resistant to macrophomina phaseolina by field screening

Submitted to: Plant Health Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 20, 2013
Publication Date: N/A

Interpretive Summary: Charcoal rot is a disease of soybean caused by the fungus (mold) Macrophomina phaseolina that causes significant economic yield losses in the United States and around the world. Efforts to manage charcoal rot in soybean through cultural practices, fungicide applications and biological control had limited effects on disease severity. Host resistance may be the only feasible method to manage this disease. Forty three of 635 accessions from the U.S. Department of Agriculture soybean germplasm collection representing maturity groups (MG) 00 to VII, showed moderate disease severity when evaluated in Missouri, Illinois and Tennessee. All except one had fungal colony forming units much less than the moderately resistant line DT97-4290. Four of the accessions: PI 518772 (MG V), PI 594302 (MG VII), PI 567562A (MG IV) and PI 506764 (MG VII) however, had the least fungal colony forming units ranging from 0 to 66. This is the first report of soybean accessions with better resistance to charcoal rot than DT97-4290. These accessions will have value as parents in the development of high yielding soybean varieties with better resistance to charcoal rot.

Technical Abstract: Charcoal rot of soybean, caused by Macrophomina phaseolina (Tassi) Goidanich, has been a problem for soybean farmers in the U. S. A. for many years. There are no strategies for managing the population density of this pathogen in the soil, and no commercial resistant soybean variety is available for effective management of this disease. The objective of these experiments was to identify resistant accessions from the USDA soybean germplasm collection in MG 00 to VII by field screening at three locations over years. A total of 635 accessions were evaluated using established methods for reaction to this disease in Missouri (2008 to 2010), Illinois (2008 and 2010), and Tennessee (2009 to 2010). Among the forty three accessions that showed moderate disease severity reaction (= severity value of 2) fourteen accessions with no visible root and stem discolorations were further assessed to validate their resistance using the colony forming units (CFU) of M. phaseolina from ground root and stem tissues. All except one had CFU levels of 0 to 1600 CFU/g which were much less than the moderately resistant line, DT97-4290 (2800 CFU/g). Four of the accessions, PI 518772 (MG V), PI 594302 (MG VII), PI 567562A (MG IV) and PI 506764 (MG VII) had the very low CFU levels of 0, 0, 67 and 67, respectively. This is the first report of soybean accessions with better levels of resistance than DT97-4290. These will have value in incorporating this resistance into high yielding soybean germplasm.