ARS | Publication request: Comparative Analysis of the Performance of Aspergillus flavus on Resistant and Susceptible Maize Genotypes during Infection

Submitted to: Fungal Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 27, 2010
Publication Date: January 1, 2011
Citation: Ankala, A., Bolla, B.K., Shivaji, R., Williams, W.P., Wilkinson, J. 2011. Comparative analysis of the performance of Aspergillus flavus on resistant and susceptible maize genotypes during infection. Fungal Ecology. 4:32-41.

Interpretive Summary: The fungus, Aspergillus flavus, produces aflatoxin which is toxic to livestock, pets, and wildlife and carcinogenic to humans. The presence of aflatoxin in corn grain reduces the value and marketability of the grain. Development of corn hybrids with genetic resistance to fungal infection and aflatoxin accumulation is widely considered a desirable to reduce or eliminate the problem. Successful development and identification of resistant corn germplasm requires evaluation of the performance of both fungus and corn after infection. In this study, we employed an RNA based quantification method using qRT-PCR to quantify viable fungal tissue after inoculation of developing corn ears and to compare the performances of both host and pathogen at different time points after inoculation of a susceptible and a resistant corn germplasm line. Our results suggest that A. flavus actively proliferates in both germplasm lines strains past 2 days after inoculation; however, in resistant Mp313E growth is suppressed and reduced by 7 days after inoculation. In addition to these differences in growth, the expression profile of the aflatoxin biosynthetic pathway genes suggests that onset of aflatoxin production is earlier in the Va35 maize genotype compared to the resistant counterpart. This information will be useful in producing parental inbred lines with genetic resistance to aflatoxin accumulation as well as good agronomic qualities.

Technical Abstract: Aspergillus, a mycotoxicogenic fungal genus, produces carcinogenic aflatoxins in crops like peanuts and maize. Development of fungal resistant maize cultivars is one strategy used to decrease contamination. Successful development and identification of resistant maize genotypes requires evaluation of resistance including the performance of both fungus and maize during infection. In this study, we employed an RNA based quantification method using qRT-PCR to relatively quantify viable fungal tissue as well as compare the performances of both host and pathogen at different time points after inoculation. Our results suggest that A. flavus actively proliferates in both strains past 2 dai (days after inoculation), however, in resistant Mp313E growth is suppressed and reduced by 7 dai. In addition to these differences in growth, the expression profile of the aflatoxin biosynthetic pathway genes suggests that onset of aflatoxin production is earlier in the Va35 maize genotype compared to the resistant counterpart.