Population Genetic Diversity And Ecological Adapation Of Fusarium Graminearum Species Complex From Wheat And Barley In China

Fusarium head blight or scab is an important fungal disease of wheat, barley, maize and rice in the warm and wet regions of the world. It can cause huge yield loss of grains, but more importantly, the main pathogen Fusarium graminearum produces different kinds of trichothecenes, which pose a serious threat to humans and animals health.O'Donnell et al. (2004) proposed a new hierarchical classification scheme by genealogical concordance phylogenetic species recognition (GCPSR). They suggested Fusarium graminearum is a species complex, which comprises at least 13 biogeographically structured and phylogenetically distinct species. So far, there is no comprehensive and systematic species recognition of Fusarium spp. in the new scheme in China. This study made a detailed species and chemotype identification of FHB pathogens from wheat and barely in China, detected the population genetic diversity and biological characters of the predominant populations. The aim of this research is to get a detailed species and chemotype composition of FHB pathogens from wheat and barely in China, make a better understanding of genetic variation and recombination among populations, monitor the dynamic changes of genetic structure, infer the evolution trend and ecological adapation. This will provide theoretical basis for breeding for FHB resistance, developing new disease and mycotoxin control strategys.1. Population genetic diversity of F. asiaticum from barley associated with mycotoxin This study identified the trichothecene chemotype and performed VNTR makers on 452 F. asiaticum isolates collected along the Chang Jiang River in China. This result indicated a significant correlation among population genetic structure, geographical distribution and trichothecene chemotype. Significant genetic subdivision was observed between NIV and 3ADON producers. Based on bayesian modle, we found an obvious population expansion trend at the genomic level that 3ADON population was replacing NIV population from east to west.2. Species and trichothecene chemotype determination of FHB pathogens collected from wheat We collected the diseased ears of wheat from 175 sampling sites in 15 provinces, established the largest strain and gene library of FHB pathogen from wheat in China. Species and trichothecene chemotype were determined by multilocus genotype assay. This result showed a significant geographical subdivision, F. graminearum s. str. with 15ADON chemotype dominated the Northeast and Huanghuaihai region, and F. asiaticum with 15ADON chemotype was predominant in the region of middle and lower reaches of the Chang Jiang River. In Southwest region, the most isolates belong to F. asiaticum and produced NIV.3. Population genetic diversity of Fusarium graminearum species complex collected from wheat Based on VNTR data and Bayesian modle, all strains were devided into three populations, among which we found significant genetic subdivision. Fg15ADON population was shown to be independent from the two F. asiaticum populations and it can be regarded as a single, large, randomly mating population. Frequent outcrossing has occurred between Fa3ADON and FaNIV population and many admixed isolates were detected. However, the outcrossing was unequal, significant subdivision was observed in NIV population, 33% NIV producers showed high degree of consistency with 3ADON in the genome. This revealed a potential biased gene flow from 3ADON to NIV producers and indicated an obvious population expansion trend at the genomic level that 3ADON population was replacing NIV population, the replacing may be due to recombination.4. Ecological adapation of different populations of Fusarium graminearum species complex collected from wheatWe selected twenty strains from each population randomly for seven biological characters test. The Fa3ADON population showed significant advantages over FaNIV population in all seven tests, they showed high pathogenicity and biomass to wheat, produced more and larger conidia, more trichothecene mycotoxin, had a higher radial growth and higher resistance to MBC. Fa3N population showed significant higher value in conidia production, conidial length and the resistance to MBC. The tests validated the result of population genetic diversity analysis, indicating that Fa3ADON is the predominant population with higher ecological adapation, so its population expansion is reasonable. We also developed a high throughput method for MBC resistant isolates determination using high-resolution melting analysis.