|Williams, William - Paul|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 10/16/2006
Publication Date: 5/17/2007
Citation: Windham, G.L., Williams, W.P. 2007. Systemic movement of Aspergillus parasiticus in maize stalks and ears [abstract]. In: Proceedings of the 2006 Multicrop Aflatoxin/Fumonisin Elimination & Fungal Genomics Workshop, October 16-18, 2006, Ft. Worth, Texas. p. 113.
Technical Abstract: Preharvest infection of corn (Zea mays) kernels by Aspergillus flavus and A. parasiticus is a chronic problem in the southern United States. It has been reported that these fungi infect developing kernels via the silk. This study was conducted to explore other avenues of infection of corn ears by Aspergillus spp. An A. parasiticus NOR mutant (NRRL 6111) was cultured in Petri dishes containing V-8 agar with sterilized toothpicks placed on the surface. Corn hybrids resistant and susceptible to aflatoxin contamination were grown in the field and inoculated at the VT stage by inserting the infested toothpicks into stalks between the 5th and 6th node below the lowest ear shoot. Beginning two weeks after inoculation, fungal growth and movement was determined weekly by collecting ear shank tissue and stalk tissue from the nodes between the infection sites and the developing ears. Cross sections of the stalks and ear shanks were dipped in ethanol, flame sterilized, and placed in Petri dishes containing Czapek solution agar amended with NaCl (7.5%). Ears were collected at the end of the growing season to determine the level of kernel infection by the NOR mutant. Kernels from individually shelled ears were surface sterilized with NaOCl and plated in Petri dishes containing Czapek solution agar amended with NaCl. The A. parasiticus NOR mutant was isolated from all stalk node tissues and ear shank tissue in the resistant and suceptible hybrids at the first collection date two weeks after inoculation. The NOR mutant was isolated from kernels of the susceptible hybrids in 2003 and 2004. Infection rates of kernels in infected ears were very low (< 1.0 %). In 2005, the fungus was found in only one kernel from an ear of the resistant hybrid. The NOR mutant was never isolated from stalks, ears, or kernels from control (uninoculated) plants grown in the plots with inoculated plants. Although infection levels of maize kernels was low, systemic movement of the A. parasiticus up the stalk appears to be another possible infection route to developing corn ears.