|Rowe, Dennis -|
Submitted to: Toxin Reviews
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 19, 2010
Publication Date: December 1, 2010
Citation: Henry, W.B., Krakowsky, M.D., Windham, G.L., Williams, W.P., Scully, B.T., Rowe, D.E., Hawkins, L.K. 2010. Comparison of the side-needle and knife techniques for inducing Aspergillus flavus infection and aflatoxin accumulation in corn hybrids. Toxin Reviews. 29:123-129. Interpretive Summary: Aflatoxin is a deadly toxin produced by a fungus that infects corn. It is a worldwide problem. One of the best ways to avoid toxin contamination is to grow corn that is resistant to fungal infection and toxin accumulation. Corn plants are evaluated for aflatoxin resistance at research stations throughout the Southern U.S. This study was conducted to compare two methods for evaluating hybrid corn. The two inoculation methods evaluated in this experiment were a needle and a knife. Both inoculation methods were used successfully to identify one resistant hybrid with low aflatoxin and three susceptible hybrids with high aflatoxin. Either inoculation method appears to be suitable for evaluating resistant and susceptible corn hybrids. The Mississippi State location produced corn with the highest Aflatoxin levels in 2007 and inoculating corn plants with the needle appeared to consistently generate more toxin than corn inoculated with the knife. The most effective inoculum concentration was 104 which was unexpected. Most corn inoculation studies typically use a higher concentration, 107. More fungal spores in the inoculum did not result in more Aflatoxin in the corn.
Technical Abstract: Aflatoxin in corn grain is a problem in many areas of the world. Any combination of environmentally stressful or agronomically unfavorable conditions can increase the likelihood of Aspergillus flavus infection and production of aflatoxin in the corn grain. In the absence of a consistent natural A. flavus infection, it is a standard practice to artificially inoculate ears of corn with a suspension of conidia to facilitate evaluation of corn gentoypes for resistance to aflatoxin acculumation. An experiment was conducted to compare side-needle and knife A. flavus inoculation techniques by measuring aflatoxin accumulation in the grain of four corn hybrids. Evaluation of the aflatoxin data with respect to distinguishing among four hybrids resulted in the same result for both inoculation techniques. The three susceptible hybrids did not differ statistically in aflatoxin accumulation, but all were significantly different from the resistant hybrid with the side-needle (P = 0.002) and the knife (P = 0.001) techniques. Aflatoxin levels varied significantly across site years. Averaged across hybrids, inoculation techniques, and inoculum concentrations, aflatoxin accumulation in the grain was highest at the Mississippi State location in 2007 (167 ng g-1) followed by Tifton in 2007 (106.7 ng g-1) and Tifton in 2008 (60.3 ng g-1). More importantly the relative performance of side-needle and knife inoculation techniques did not change or interact significantly across site years (P = 0.171) suggesting that both the needle and knife are consistent inoculation techniques for discriminating between resistant and susceptible corn hybrids at these locations. The side-needle technique resulted in higher levels of aflatoxin accumulation in the corn grain and the 104 inoculum concentration resulted in the highest aflatoxin response.