Abstract
Fusarium head blight (FHB) is a complex disease of cereals caused by Fusarium species, which causes severe damages in terms of yield quality and quantity worldwide, and which produces mycotoxin contamination, posing a serious threat to public health. In the study presented herein, the antifungal activity against Fusarium culmorum of chitosan oligomers (COS)–amino acid conjugate complexes was investigated both in vitro and in vivo. The amino acids assayed were cysteine, glycine, proline and tyrosine. In vitro tests showed an enhancement of mycelial growth inhibition, with EC50 and EC90 effective concentration values ranging from 320 to 948 µg·mL−1 and from 1107 to 1407 µg·mL−1 respectively, for the conjugate complexes, as a result of the synergistic behavior between COS and the amino acids, tentatively ascribed to enhanced cell membrane damage originating from lipid peroxidation. Tests on colonies showed a maximum percentage reduction in the number of colonies at 1500 µg·mL−1 concentration, while grain tests were found to inhibit fungal growth, reducing deoxynivalenol content by 89%. The formulation that showed the best performance, i.e., the conjugate complex based on COS and tyrosine, was further investigated in a small-scale field trial with artificially inoculated spelt (Triticum spelta L.), and as a seed treatment to inhibit fungal growth in spelt seedlings. The field experiment showed that the chosen formulation induced a decrease in disease severity, with a control efficacy of 83.5%, while the seed tests showed that the treatment did not affect the percentage of germination and resulted in a lower incidence of root rot caused by the pathogen, albeit with a lower control efficacy (50%). Consequently, the reported conjugate complexes hold enough promise for crop protection applications to deserve further examination in larger field trials, with other Fusarium spp. pathogens and/or Triticum species.
Highlights
Fusarium head blight (FHB) is a devastating fungal disease that affects wheat and other small-grain cereals worldwide, caused by several species belonging to the genus Fusarium
The treatments based solely on amino acids showed a lower performance than the treatments including chitosan oligomers (COS), either alone or in combination with the amino acids (Figure 2)
Upon increase of the concentration, higher inhibition was attained for all treatments, except for the glycine only treatment, in which fungal inhibition remained below 30%
Summary
Fusarium head blight (FHB) is a devastating fungal disease that affects wheat and other small-grain cereals worldwide, caused by several species belonging to the genus Fusarium. Besides causing significant yield losses and reducing grain quality [1], these species are able to biosynthesize mycotoxins harmful to both humans and animals [2,3]. F. graminearum Schwabe are generally considered the two most important FHB causal agents worldwide [4], but F. poae, F. asiaticum, F. boothii, F. vorosii and F. cortaderiae pose a serious threat [5].
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