RT Journal Article SR Electronic T1 Low aflatoxin levels and flowering delay in Aspergillus flavus-resistant maize lines are correlated with increased corn earworm damage and enhanced seed fumonisin content JF bioRxiv FD Cold Spring Harbor Laboratory SP 2020.02.03.933309 DO 10.1101/2020.02.03.933309 A1 Subbaiah Chalivendra A1 Fangneng Huang A1 Mark Busman A1 W. Paul Williams A1 Jong Hyun Ham A1 Geromy G. Moore YR 2020 UL http://biorxiv.org/content/early/2020/02/04/2020.02.03.933309.abstract AB Preharvest mycotoxin contamination of field-grown crops is influenced not only by the host genotype, but also inoculum load, insect pressure and their confounding interactions with seasonal weather. In two field trials, we observed a preferred natural infestation of specific maize (Zea mays L.) genotypes by corn earworm (Helicoverpa zea Boddie) and investigated this unexpected interaction. These studies involved four maize lines with contrasting levels of resistance to Aspergillus flavus. The resistant lines had 7 to 14-fold greater infested ears than the susceptible lines. However, seed aflatoxin B1 levels, in mock- or A. flavus-inoculated ears were consistent with maize genotype resistance to A. flavus. Further, the corn earworm-infested ears had greater levels of fumonisin content in seeds than uninfested ears, indicating that the insect may have vectored native Fusarium verticillioides inoculum. The two maize lines with heavy infestation showed delayed flowering. The availability of young silk for egg-laying could have been a factor in the pervasive corn earworm damage of these lines. At the same time, H. zea larvae reared on AF-infused diet showed decreasing mass with increasing AF and >30% lethality at 250 ppb. In contrast, corn earworm was tolerant to fumonisin with no significant loss in mass even at 100 ppm, implicating the low seed aflatoxin content as a predominant factor for the prevalence of corn earworm infestation and the associated fumonisin contamination in A. flavus resistant lines. These results highlight the need for integrated strategies targeting mycotoxigenic fungi and their insect vectors to enhance the safety of crop commodities.IMPORTANCE Aspergillus and Fusarium spp. not only cause ear rots in maize leading to crop loss, they can also contaminate the grain with carcinogenic mycotoxins. Incorporation of genetic resistance into breeding lines is an ideal solution for mycotoxin mitigation. However, the goal is fraught by a major problem. Resistance for AF or FUM accumulation is quantitative and contributed by several loci with small effects. Our work reveals that host phenology (flowering time) and insect vector-mycotoxin interactions can further confound breeding efforts. A host genotype even with demonstrable resistance can become vulnerable due to seasonal variation in flowering time or an outbreak of chewing insects. Incorporation of resistance to a single mycotoxin accumulation and not pairing it with insect resistance may not adequately ensure food safety. Diverse strategies including host-induced silencing of genes essential for fungal and insect pest colonization and broad-spectrum biocontrol systems need to be considered for robust mycotoxin mitigation.