Submitted to: Phytopathology News
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/2006
Publication Date: 6/1/2006
Citation: Pabon, A., Hill, C.B., Hartman, G.L. 2006. A greenhouse method for screening for resistance to charcoal rot in soybeans [abstract]. American Phytopathological Society Abstracts. 96:S88.
Technical Abstract: The fungus Macrophomina phaseolina (Tassi) Goid causes charcoal rot disease of soybean (Glycine max (L.) Merr.) and several other susceptible host species. The pathogen invades the roots, colonizes the vascular system, and interferes with water transport. Under conditions favorable for disease, such as low soil moisture and high ambient temperatures, significant economic losses of up to 77% have been reported in soybean. Partial resistance to the disease has been found in soybean and other host species. Field screening methods have been primarily used to identify partial resistant soybean genotypes. A greenhouse method for screening soybean germplasm for resistance to charcoal rot has been developed. Agar plugs (5 mm diameter) taken from the margin of actively growing M. phaseolina cultures on PDA with pipette tips (1-200 microliters) are placed over the tips of V1-V2 stage soybean stems cut down to 5 cm above the cotyledon node by capping. Post-inoculated plants are incubated in a growth chamber at 30 deg C with a photoperiod of 12 hours until the fungus kills the susceptible check plants. Partial resistance is measured by the percent of plants killed in eight-plant experimental units. Experiments are in progress to determine the repeatability of the test and correlation of results with other screening methods, including field tests.