Database Research Summaries2017 Genetic Population Structure of M. phaseolina
Research Focus
The focus of this project is to study the genetic variability in this pathogen, principally to aid soybean breeders in developing charcoal-rot resistant cultivars and to aid Ohio farmers in developing disease management strategies.
Objectives
- Compare the population structure of Macrophomina phaseolina (causal agent of charcoal rot of soybean) isolates from fields in Ohio and other states and fields in South America.
- Compare the geographically distant populations for genetic relationships.
Results
- The isolates were grouped into three Ohio regions (North, Central and South). Isolate growth were compared between these regions for each of the five different temperature conditions. M. phaseolina isolates from North and Central regions grew significantly faster than isolates from South Ohio. As temperature increased and reached the fungus optimum growing temperature isolates from South Ohio grew similar to those from northern regions.
- A total of 200 M. phaseolina isolates were used in the pathogenicity study. Isolates were assigned a geographic region by slightly modifying the Ohio Agricultural Statistics Districts designations. These isolates of M. phaseolina were obtained from soil collected throughout soybean and cornfields in Ohio.
- A cut-stem inoculation technique was used to evaluate the pathogenicity and aggressiveness of M. phaseolina isolates. Briefly, stem apex was cut 25 mm above the unifoliate node and a PDA plug with actively growing M. phaseolina mycelia (or not in the case of the negative control) was set on top of the cut and covered with a pipette tip. Three days after tips were removed and length of the necrotic lesion from the top of the cut stem was measured every day for thirteen days.
- Macrophomina phaseolina isolates from soil samples collected from soybean and cornfields in Ohio were all pathogenic to soybean. Moreover, M. phaseolina isolates displayed a significant variation in aggressiveness. Macrophomina phaseolina was never recovered from negative control and AUDPC was zero.
- A physiological and pathogenicity assays (similar to those performed with the Ohio isolates to produce the phenotypic results presented in this report) were conducted on M. phaseolina isolates from South America. Data is now being compiled and analyzed to further compare with results obtained from assay with M. phaseolina isolates from Ohio.
For more information about this research project, please visit the National Soybean Checkoff Research Database.
Funded in part by the soybean checkoff.
