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ARS Home » Southeast Area » Mississippi State, Mississippi » Crop Science Research Laboratory » Corn Host Plant Resistance Research » Research » Publications at this Location » Publication #271789

Title: Tissue-specific components of resistance to Aspergillus ear rot of maize

Author
item MIDEROS, SANTIAGO - Cornell University - New York
item Windham, Gary
item Williams, William
item NELSON, REBECCA - Cornell University - New York

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/30/2012
Publication Date: 7/10/2012
Citation: Mideros, S.X., Windham, G.L., Williams, W.P., Nelson, R.J. 2012. Tissue-specific components of resistance to Aspergillus ear rot of maize. Phytopathology. 102:787-793.

Interpretive Summary: Aflatoxin contamination of corn by the fungus Aspergillus flavus is a major problem for producers in the southern United States. The most desirable method for controlling aflatoxin contamination in corn is the use of resistant plants. Inbred lines that have resistance to colonization by A. flavus or to aflatoxin accumulation have been released by the USDA-ARS. However, the mechanisms of resistance are not known. Studies were conducted in field and greenhouse experiments to gain a better understanding of the resistance mechanisms in corn kernels and in silks. Measures of resistance/susceptibility that were monitored in the experiments included 1) the extent of A. flavus colonization by means of quantitative PCR assay, 2) the timing and extent of sporulation, and 3) the level of aflatoxin accumulation. Kernel composition traits (fiber, ash, carbohydrate and seed weight) were quantified to determine their effects on resistance. Corn lines did vary in susceptibility to silk and kernel colonization by A. flavus. There was a significant correlation of resistance to aflatoxin accumulation with flowering time and kernel composition traits. Our findings suggest that the genetic portion of resistance to aflatoxin accumulation is due to resistance to A. flavus colonization. Also, lines that flower later in the season tend to be more resistant, which may involve avoidance mechanisms.

Technical Abstract: Aspergillus flavus and other Aspergillus spp. infect maize and produce aflatoxins. One control measure is the use of resistant maize lines. There are several reports of maize lines that are resistant to aflatoxin accumulation, but the mechanisms of resistance remain unknown. To gain a better understanding of resistance, we dissected the phenotype into ten components: four pertaining to the response of silk and six pertaining to the response of kernels to inoculation with A. flavus. Replicated inoculation experiments were conducted in-vitro and under field conditions on a panel of diverse maize inbreds over three years. As usual for this trait, a significant genotype-by-environment interaction was found for all the components of resistance studied. We found, however, compelling evidence that there is variation in maize germplasm for susceptibility to silk and kernel colonization by A. flavus. In addition, we found a significant correlation of resistance to aflatoxin accumulation with flowering time and kernel composition traits (fiber, ash, carbohydrate and seed weight). Our results suggest that the genetic portion of resistance to aflatoxin accumulation is due to resistance to A. flavus colonization. Lines that flower later in the season tend to be more resistant, which may involve avoidance mechanisms.