Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 10/23/2002
Publication Date: 2/1/2003
Citation: Magbanua, Z.V., Williams, W.P., Windham, G.L., Luthe, D.S. 2003. Use of GFP-tagged Aspergillus flavus to monitor fungal growth in developing ears of resistant and susceptible corn hybrids [abstract]. Proceedings of the 2nd Fungal Genomics, 3rd Fumonisin Elimination and 15th Alfatoxin Elimination Workshops. p. 151.
Technical Abstract: We used a GFP-transformed Aspergillus flavus strain to needle inoculate mid-maturation ears and follow the path of fungal invasion in resistant and susceptible hybrids of Zea mays. In all ear cross-sections examined, the level of fluorescence was higher in susceptible compared to resistant lines. Our data suggest an extensive penetration of the rachis tissues from 1 to 5 days post-inoculation in susceptible but not resistant lines. At 10 and 20 days post-inoculation, fluorescence levels were low (slightly over background) and did not differ significantly between resistant and susceptible lines. We observed differences in fluorescence expression in the endosperm and embryos of all lines. In susceptible lines, the fungus appeared to preferentially grow from the mid-ear inoculation site to the tip of the ear. There was less fluorescence in sections taken toward the base of the ear. This may indicate that the fungus uses nutrient flow inside the ear to achieve systemic infection. While data analysis is still ongoing, we present a model for A. flavus invasion of the ear. The fungus enters through wounding of the ear or by capture of fungal spores by the silk. Both of these cases potentially could lead to penetration of the rachis tissues and eventually to invasion of the rachilla, pith, pericarp, endosperm and embryos as early as 1 to 3 days post-inoculation in susceptible plants. Successful invasion must occur at mid-maturation ear, when all the necessary nutrients for optimum fungal growth are available.