Genetic diversity of Fusarium meridionale, F. austroamericanum, and F. graminearum isolates associated with Fusarium head blight of wheat in Brazil

Abstract

One of the biggest challenges of wheat production worldwide is to overcome fungal diseases, and among these is Fusarium head blight (FHB) caused mainly by the Fusarium graminearum species complex (FGSC). The occurrence of FHB can lead to contamination of grains with mycotoxins, which are harmful to human and animal health. In South America, in addition to F. graminearum sensu stricto (F. graminearum), which is the most common causal agent of FHB worldwide, F. meridionale and F. austroamericanum have also been found in wheat fields. Special attention should be paid to F. meridionale because it produces the trichothecene mycotoxin nivalenol, which has potentially higher levels of toxicity when compared with that of other trichothecene produced by the FGSC. Knowledge of the diversity and genetic structure of populations of pathogens can assist in understanding pathogen survival in the face of host genetic resistance, crop rotation, and management with fungicides. In this study, we used 10 inter-simple sequence repeat (ISSR) primers to estimate the variability, diversity, and genetic structure of populations of F. graminearum, F. meridionale, and F. austroamericanum co-occurring in wheat fields in Paraná State, Brazil. The population of F. graminearum showed the greatest genetic variability according to its polymorphism (P = 86.61%), Nei's genetic diversity (h = 0.28), and Shannon diversity (I = 0.43) indices as compared with that of the populations of F. meridionale (P = 75.89%, h = 0.23, I = 0.36) and F. austroamericanum (P = 67.86%, h = 0.22, I = 0.33). The dendrogram, principal coordinate analysis, Bayesian analysis (K = 4), and the differentiation index (G ST = 0.27) showed very high structure and, consequently, high species differentiation. The overall analysis of our data indicates high variability and genetic structure of the studied populations. This genetic condition guarantees high resilience of these species and could make it difficult to obtain wheat cultivars with good resistance to FHB, as well as may cause chemical control to be less effective.

Breeding Tools for Assessing and Improving Resistance and Limiting Mycotoxin Production by Fusarium graminearum in Wheat

“…Ingestion of huge amounts of mycotoxin contaminated grain may lead to mycotoxicosis, which under severe circumstances may cause death. It is important to note that there is very high genetic variability of F. graminearum species, which results in high resilience and complicates efforts towards breeding for FHB resistance due to genotype by isolate and isolate by environment interactions [ 8 ].…”