Updating the Methodology of Identifying Maize Hybrids Resistant to Ear Rot Pathogens and Their Toxins—Artificial Inoculation Tests for Kernel Resistance to Fusarium graminearum, F. verticillioides, and Aspergillus flavus

Abstract

Resistance to toxigenic fungi and their toxins in maize is a highly important research topic, as mean global losses are estimated at about 10% of the yield. Resistance and toxin data of the hybrids are mostly not given, so farmers are not informed about the food safety risks of their grown hybrids. According to the findings aflatoxin regularly occurs at preharvest in Hungary and possibly other countries in the region can be jeopardized. We tested, with an improved methodology (two isolates, three pathogens, and a toxin control), 18 commercial hybrids (2017–2020) for kernel resistance (%), and for toxin contamination separately by two–two isolates of F. graminearum, F. verticillioides (mg/kg), and A. flavus (μg/kg). The preharvest toxin contamination was measured in the controls. Highly significant kernel resistance and toxin content differences were identified between hybrids to the different fungi. Extreme high toxin production was found for each toxic species. Only about 10–15% of the hybrids showed higher resistance to the fungal species tested and lower contamination level of their toxins. The lacking correlations between resistance to different fungi and toxins suggest that resistance to different fungi and response to toxin contamination inherits independently, so a toxin analysis is necessary. For safety risk estimation, separated artificial and natural kernel infection and toxin data are needed against all pathogens. Higher resistance to A. flavus and F. verticillioides stabilizes or improves feed safety in hot and dry summers, balancing the harmful effect of climate changes. Resistance and toxin tests during variety registration is an utmost necessity. The exclusion of susceptible or highly susceptible hybrids from commercial production results in reduced toxin contamination.

Changes in Fusarium and Aspergillus Mycotoxin Content and Fatty Acid Composition after the Application of Ozone in Different Maize Hybrids

“…Very warm and rainy July (heat wave from 6 to 16 July and precipitation above 90 mm), and warm and dry August (heat wave from 25 July to 2 August and precipitation 35 mm) in 2021 [ 58 ] are favorable for ear rot development. Although all genotypes are affected under favorable conditions, hybrids differ significantly in terms of ear rot resistance and mycotoxin content [ 59 ].…”

The Role of Preharvest Natural Infection and Toxin Contamination in Food and Feed Safety in Maize, South-East Hungary, 2014–2021

“…From the naturally infected grain, several hundred fungal lines were isolated. The nucleotide sequences for species determination were as follows: F. graminearum and F. verticillioides : EF1-α primers: ef1: ATGGGTAAGGARGACAAGAC and ef2: GGARGTACCAGTSATCATGTT; A. flavus : CaM primers: CMD5: CCGAGTACAAGGARGCCTTC and CMD6: CCGATRGAGGTCATRACGTGG [ 48 ]. F. graminearum and F. verticillioides were dominant.…”

“…The ear rot mean of the natural Aspergillus spp. was 0.002% and that of the artificial inoculation was 0.250% (a 125-fold difference) in 2019–2020 [ 48 ]. A similar natural infection was recognized in the corn nursery, far from this experimental site.…”

“…Rather, authors think that biocontrol using an atoxic A. flavus strain [ 46 , 47 ] can be more successful. In Hungary, Mesterhazy et al (2022) [ 48 ] published artificial inoculation result for F. graminearum, F. verticillioides , and A. flavus. In the non-inoculated sample, DON, FUM B 1 +B 2, and AFB1 were also controlled.…”

“…The work in [ 41 ] is important because it showed that beside the temperature also humidity is needed for disease spread and toxin contamination. The toxin contamination for a percentage of the visual scores was recognized in artificial inoculation tests [ 48 ]; in this paper, we test this for natural infection.…”