Comparison of different inoculating methods to evaluate the pathogenicity and virulence of Aspergillus niger on two maize hybrids
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A two-year field study was conducted to determine the effects of artificial inoculation techniques on the pathogenicity and virulence of Aspergillus niger kernel infection on two maize hybrids. Test plants included in the study were hybrids resistant and susceptible to Aspergillus flavus to determine if the host resistance mechanisms that limited A. flavus infection would also suppress A. niger infection. Ears were inoculated with the silk-channel, side-needle, and spray techniques 7 days after midsilk (50% of the plants in a plot had silk emerging). Ears were also inoculated with a modified-pinbar technique 21 days after midsilk. Kernel infection in 2008 in inoculated plants ranged from 2% to 11% and from 2% to 45% in the resistant and susceptible hybrids, respectively. In 2009, kernel infection in inoculated plants ranged from 13% to 32% and from 10% to 67% in the resistant and susceptible, respectively. The silk-channel, side-needle, and modified-pinbar techniques produced significantly higher levels of kernel infection in the susceptible hybrid in both years than the spray technique. When hybrids were compared, the silk-channel, side-needle, and modified-pinbar techniques induced significantly higher levels of infections in the susceptible hybrid than in the resistant hybrid in 2008 and 2009. The level of A. niger pathogenicity and virulence increased when conidia were placed inside the husks of developing ears by wounding (modified-pinbar and side-needle techniques) or non-wounding (silk-channel technique) inoculation methods. Although A. niger kernel infection was significantly lower in the A. flavus resistant hybrid compared to the A. flavus susceptible hybrid, A. niger infection levels were much higher than A. flavus infection levels typically observed in both of these hybrids in past studies.
KeywordsAspergillus flavus Corn Kernel infection Zea mays
The authors thank Mike Alpe, Greg Flint, Gerald Matthews, and Ladonna Owens for excellent technical assistance. This article reports the results of research only. Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the USDA or Mississippi State University. This article is a contribution of the USDA-ARS in cooperation with the Mississippi Agricultural and Forestry Experiment Station, Mississippi State, MS. It is published with the approval of both agencies.
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