The fungal pathogen, Macrophomina
phaseolina (Mp), causes
the disease charcoal rot (CR), which can greatly impact soybean production.
This disease is typically more prevalent in the southern US soybean producing
areas, but has become more of a problem in the northern US in the last decade.
Host resistance to CR is the primary means of managing this disease, yet
resistance in commercial soybean varieties in Maturity Groups (MG) I-III,
soybeans adapted for use in the northern US, is currently unknown. To address
this emerging problem in the northern US, our research targeted both the host
and pathogen. Commercial soybean varieties available for use in the northern US
(MG I-III) were screened for resistance to CR using a greenhouse “cut-stem”
assay, and multiple potential moderately resistant varieties were identified. M. phaseolina isolates native to the
northern US were compared with southern isolates to identify differences in
growth and development when exposed to various temperatures. Clear temperature
preferences were apparent. Isolate populations were also compared based on
disease reactions on different soybean varieties. Experiments showed that
disease reactions can vary based on the individual isolate used.