Fusarium head blight resistance exacerbates nutritional loss of wheat grain at elevated CO2

The nutritional integrity of wheat is jeopardized by rapidly rising atmospheric carbon dioxide (CO2) and the associated emergence and enhanced virulence of plant pathogens. To evaluate how disease resistance traits may impact wheat climate resilience, 15 wheat cultivars with varying levels of resistance to Fusarium Head Blight (FHB) were grown at ambient and elevated CO2. Although all wheat cultivars had increased yield when grown at elevated CO2, the nutritional contents of FHB moderately resistant (MR) cultivars were impacted more than susceptible cultivars. At elevated CO2, the MR cultivars had more significant differences in plant growth, grain protein, starch, fructan, and macro and micro-nutrient content compared with susceptible wheat. Furthermore, changes in protein, starch, phosphorus, and magnesium content were correlated with the cultivar FHB resistance rating, with more FHB resistant cultivars having greater changes in nutrient content. This is the first report of a correlation between the degree of plant pathogen resistance and grain nutritional content loss in response to elevated CO2. Our results demonstrate the importance of identifying wheat cultivars that can maintain nutritional integrity and FHB resistance in future atmospheric CO2 conditions.

Characterizing Winter Wheat Germplasm for Fusarium Head Blight Resistance Under Accelerated Growth Conditions

Fusarium head blight (FHB) is one of the economically important diseases of wheat as it causes severe yield loss and reduces grain quality. In winter wheat, due to its vernalization requirement, it takes an exceptionally long time for plants to reach the heading stage, thereby prolonging the time it takes for characterizing germplasm for FHB resistance. Therefore, in this work, we developed a protocol to evaluate winter wheat germplasm for FHB resistance under accelerated growth conditions. The protocol reduces the time required for plants to begin heading while avoiding any visible symptoms of stress on plants. The protocol was tested on 432 genotypes obtained from a breeding program and a genebank. The mean area under disease progress curve for FHB was 225.13 in the breeding set and 195.53 in the genebank set, indicating that the germplasm from the genebank set had higher resistance to FHB. In total, 10 quantitative trait loci (QTL) for FHB severity were identified by association mapping. Of these, nine QTL were identified in the combined set comprising both genebank and breeding sets, while two QTL each were identified in the breeding set and genebank set, respectively, when analyzed separately. Some QTLs overlapped between the three datasets. The results reveal that the protocol for FHB evaluation integrating accelerated growth conditions is an efficient approach for FHB resistance breeding in winter wheat and can be even applied to spring wheat after minor modifications.

Evaluation of Genomic Prediction for Fusarium Head Blight Resistance with a Multi-Parental Population

Fusarium head blight (FHB) resistance is quantitatively inherited, controlled by multiple minor effect genes, and highly affected by the interaction of genotype and environment. This makes genomic selection (GS) that uses genome-wide molecular marker data to predict the genetic breeding value as a promising approach to select superior lines with better resistance. However, various factors can affect accuracies of GS and better understanding how these factors affect GS accuracies could ensure the success of applying GS to improve FHB resistance in wheat. In this study, we performed a comprehensive evaluation of factors that affect GS accuracies with a multi-parental population designed for FHB resistance. We found larger sample sizes could get better accuracies. Training population designed by CDmean based optimization algorithms significantly increased accuracies than random sampling approach, while mean of predictor error variance (PEVmean) had the poorest performance. Different genomic selection models performed similarly for accuracies. Including prior known large effect quantitative trait loci (QTL) as fixed effect into the GS model considerably improved the predictability. Multi-traits models had almost no effects, while the multi-environment model outperformed the single environment model for prediction across different environments. By comparing within and across family prediction, better accuracies were obtained with the training population more closely related to the testing population. However, achieving good accuracies for GS prediction across populations is still a challenging issue for GS application.

Genetic trends in Fusarium head blight resistance due to 20 years of winter wheat breeding and cooperative testing in the Northern US.

Fusarium head blight (FHB) is a devastating disease of wheat and barley. In the US, a significant long-term investment in breeding FHB resistant cultivars began after the 1990s. However, to this date, no study has been performed to understand and monitor the rate of genetic progress in FHB resistance as a result of this investment. Using 20 years of data (1998 to 2018) from the Northern Uniform (NU) and Preliminarily Northern Uniform (PNU) winter wheat scab nurseries which consisted of 1068 genotypes originating from 9 different institutions, we studied the genetic trends in FHB resistance within the northern soft red winter wheat growing region using mixed model analyses. For the FHB resistance traits incidence, severity, Fusarium damaged kernels (FDK), and deoxynivalenol content, the rate of genetic gain in disease resistance was estimated to be 0.30 ± 0.1, 0.60 ± 0.09, 0.37 ± 0.11 points per year, and 0.11 ± 0.05 ppm per year, respectively. Among the five FHB resistance QTL assayed for test entries from 2012 to 2018, the frequencies of favorable alleles from Fhb 2DL Wuhan1 W14, Fhb Ernie 3Bc, and Fhb 5A Ning7840 was close to zero across the years. The frequency of the favorable at Fhb1 and Fhb 5A Ernie ranged from 0.08 to 0.33 and 0.06 to 0.20 respectively across years, and there was no trend in changes in allele frequencies over years. Overall, this study showed that substantial genetic progress has been made towards improving resistance to FHB. It is apparent that the current investment in public wheat breeding for FHB resistance is achieving results and will continue to play a vital role in reducing FHB levels in growers’ fields.

Transfer of Fusarium Head Blight Resistance from Thinopyrum elongatum to bread wheat cultivar Chinese Spring

The diploid form of Tall Wheatgrass, Thinopyrum elongatum (Host) D. R. Dewey (2n = 2x = 14, EE genome) has a high level of resistance to Fusarium head blight. The symptoms do not spread beyond the inoculated floret following point inoculation. Using the series of E genome chromosome additions in a bread wheat cultivar Chinese Spring (CS) background, the resistance was found to be localized to the long arm of chromosome 7E. CS mutant ph1b was used to induce recombination between chromosome 7E, present in the 7E(7D) substitution and homoeologous wheat chromosomes. Multivalent chromosome associations were detected in BC1 hybrids attesting to the effectiveness of the ph1b mutant. Genetic markers specific for chromosome 7E were used to estimate the size of the 7E introgression in the wheat genome. Using single sequence repeat (SSR) markers specific for homoeologous wheat chromosome 7, introgressions were detected on wheat chromosomes 7A, 7B and 7D. Some of the introgression lines were resistant to Fusarium head blight.

Exploring Fusarium Head Blight Resistance In a Winter Triticale Germplasm Collection

Fusarium Head Blight (FHB) is a destructive disease affecting the grain yield and quality of wheat, barley, rye and triticale. Developing varieties with genetic resistance is integral to successfully managing FHB. However, significant knowledge gap exists in the genetic diversity present in triticale for FHB resistance. This information is critical for breeding new varieties of triticale as its production continues to increase. In the present study, a set of 298 winter triticale accessions from a worldwide collection were screened for their type-2 FHB resistance in an artificially inoculated misted nursery with high levels of inoculum density. Most of the triticale accessions were susceptible to FHB, and only 8% of accessions showed resistance in the field nursery screening. The resistant accessions identified in the nursery screening were selected and further screened for three years in greenhouse conditions. Seven accessions were found to show robust FHB resistance over the three years of greenhouse testing. Thirteen accessions showed significantly lower levels of Deoxynivalenol accumulation when compared to the susceptible triticale control. The accessions identified in the study will be useful in triticale and wheat breeding programs for enhancing FHB resistance and reducing DON accumulation.

Genome-Wide Association Study and QTL Mapping Revealed Genetic Loci for Fusarium Head Blight Resistance in Chinese Hexaploid Wheat

Fusarium Head Blight (FHB) greatly affects wheat yield worldwide and could also downgrade quality. In this study, a total of 406 wheat cultivars were investigated for FHB disease index (DI). Results indicated that the FHB DI of 95% of the tested cultivars showed more than scale 2. Genome-wide association study (GWAS) identified 321 SNPs significantly related to FHB resistance on all chromosomes with 2.71–13.32% phenotypic variance explained (PVE). An important genetic locus gFHB-5A (329,828,930 to 595,372,995 bp) was identified to modulate FHB resistance in two panels, and the incidence of resistant alleles at the gFHB-5A1a locus were increasing with time in the tested cultivars. Two loci of gFHB-2B (9,740,162 to 68,200,954 bp) with PVE values of 2.73–3.57% and gFHB-7A (515,126,041 to 537,557,064 bp) with PVE values of 2.71–7.04% were identified to be significantly associated with FHB resistance. Linkage analysis in a bi-parental population identified the QTL FHB.hau-4D flanked by markers wPt-8836 and wPt-4572 with PVE value of 8.9%. This study identified new genetic loci to control FHB resistance and provided useful information of marker-assist selection in wheat FHB resistance breeding.