Evaluation On Resistance Of Wheat Cultivars Against Fusarium Head Blight In China And Metabolome Study Associated With Pathogenicity Of Fusarium Fungi

Fusarium head blight(FHB),caused mainly by members of the Fusarium graminearum species complex,is one of the most damaging diseases of wheat worldwide and is responsible for severe reductions in wheat yield and quality.Mycotoxins can also be produced from diseased wheat,posing a potential threat to human health.In China,the Yangtze River valleys were known as the most severe FHB epidemic areas for a long time,but the disease has been spreading northward since the last decade and now the Huanghuai region,which is currently the main wheat production area of China has also become one of the most important FHB epidemic regions.The use of FHB-resistant wheat cultivars is considered to be the most cost-effective strategy to reduce occurrence and production of mycotoxins in wheat.Although a number of disease resistant cultivars have been cultivated in China,more than 90% of them are still susceptible cultivars.The reason is the lack of thorough understanding of the resistance mechanism of host and pathogenic mechanism of pathogen.In this paper,focusing on the wheat cultivars bred and approved from the upper region of the Yangtze River(UYR),the middle and lower region of the Yangtze River(MLYR),southern and northern of Huang Huai river basins(SH and NH),where FHB is frequently prevalent,the FHB resistance level,toxin accumulation level,and the correlation between them were investigated.The stability of FHB resistance level of wheat was evaluated under different environmental conditions.On the other hand,the metabolomic study associated with pathogenicity of Fusarium asiaticum,the dominant pathogen of FHB in souththern wheat region,was carried.The aim of this research is to clarify the resistance level of wheat to FHB,the resistance to toxin accumulation level in different ecological regions and the correlation between them,illuminate the stability of wheat FHB resistance level under cross-regional environment,and reveal the key biomarkers and metabolic pathways related to the disease of FHB.This will provide a theoretical basis for exploring the resistance mechanism of wheat to FHB and pathogenic mechanism of Fusarium fungi.1.Resistance to Fusarium head blight and mycotoxin accumulation of wheat cultivars from different ecological regions in China.The resistance level of 129 wheat cultivars collected from four ecological regions in China was evaluated based on disease index(DI)as index by field tests of FHB resistance after natural infection.The disease index of 129 wheat cultivars ranged from 6.3% to 80.9%,and most of them were susceptible cultivars(82.2%).The middle and lower reaches of Yangtze River region showed the highest disease resistance,followed by the upper reaches of the Yangtze River region.FHB resistance of cultivars from northern and southern Huanghuai region was lowest and all cultivars in these regions were highly or moderately susceptible.The accumulation levels of 6 toxins(deoxynivalenol DON,zearalenone ZEN,3-acetyldeoxynivalenol 3-ADON,15-acetyldeoxynivalenol 15-ADON,T-2 and HT-2 toxin)in grain were analyzed by ultra-high performance liquid chromatography tandem mass spectrometry(UPLC-MS/MS).The average contents of DON,3-ADON,15-ADON,ZEN and T-2 toxin were 2.35 mg/kg,0.41 mg/kg,0.09mg/kg,0.11 mg/kg and 0.28 mg/kg,respectively.HT-2 toxin was not detected in the samples.Correlation analysis between disease index and toxin accumulation was also performed by generalize linear model(GLM).The results showed that disease index was significantly correlated with toxin accumulation on nationwide,but no clear correlation was found within most ecological regions.Under the same FHB resistance level,cultivars from the Yangtze River regions had a higher level of resistance to toxin accumulation than those from the Huanghuai regions.2.Stability evaluation of wheat cultivars resistance to FHB in different ecological environments.In three nurserieswith different climatic conditions,theresistancelevelof410 wheat cultivars collected from four ecological regions in China were evaluated basedon DIby field tests of FHB resistance after natural infection.The DI isweresignificant differences among the three locations.The DIs in Nanping were the highest(77.2%),followed by Yangzhou(56.8%)and Hefei(19.9%).The interquartile range(IQR=44)of the DI in Yangzhou was the largest and the distribution was uniform,whichreflected the best discrimination of FHB resistance in cultivars in2019.The stability of FHB resistance level in the different nurseries was evaluated by quartile method and Fisher test,which showed that the distribution of resistance level in Yangzhou and Nanping nurseries was relatively stable.The accumulation levels of2 toxins(DON and Nivalenol)in grain were analyzed by UPLC-MS/MS.DON was the dominant mycotoxin in Hefei and Yangzhou,with an average content of 1.13mg/kg and 12.87 mg/kg.Nivalenol(NIV)was predominant with an average content of 7.63 mg/kg in Nanping.Growing region and cultivar had significant effect on DI and mycotoxins by GLM.By comparing the differences of five meteorological factors(temperature,humidity,rainfall,sunshine and soil surface temperature)among the three locations,it was found that humidity and rainfall were significantly different in the three locations,while the other three parameters were not significantly different between Hefei and Yangzhou,but were significantly different from Nanping.This indicated that relative humidity and rainfall were the key factors affecting the FHB severity.The change of resistance level of wheat cultivars to FHB in 2019 and 2015 was analyzed.It was found that 81.7% of tested cultivars were still susceptible in2019,but the proportion of resistant cultivars increased from 17% to 18.3%.3.Metabolome study associated with pathogenicity of Fusarium asiaticum.The metabolites produced by two populations(3-ADON and NIV)with different pathogenicity were analysed using metabonomics technology.288 compounds with significant differences were screened,which divided into 11 classes.The lipids and lipid-like molecular were the dominant(32%),followed by organic acids and derivatives(15%),benzenoids(15%).KEGG pathways analysis revealed one metabolic pathways(biosynthesis of unsaturated fatty acids)have significant effects.Three toxin intermediates,Farnesol,CAL and 15-de CAL,were analyzed by MSFINDER software.The metabolic flux toward the biosynthesis of trichothecene toxin in 3ADON population,and toward the biosynthesis of unsaturated fatty acid in NIV population.In addition,10 specific metabolites associated with pathogenicity and1010 unknown differential metabolites were found in this study.