Evaluating Inoculation Methods to Infect Sugar Beet with Fusarium oxysporum f. betae and F. secorum

Graphene Quantum Dots (GQD)-Mediated dsRNA Delivery for the Control of Fusarium Head Blight Disease in Wheat

Graphene quantum dots (GQDs), a class of fluorescent carbon materials, have displayed significant potential in various fields such as energy devices, catalysis, sensing, bioimaging, and drug delivery. Because of their extremely small size, generally less than 100 nm, they also have tremendous potential in plant science research, especially for the delivery of nucleic acids, breaking the barrier of cell walls. In this study, we synthesized GQDs with a size range of 2-5 nm, characterized them, and surface-functionalized them with branched polyethylenimine (bPEI). We then used the surface-functionalized GQDs as carriers to deliver double-stranded RNA (dsRNA) that target two growth-and-development-related genes in Fusarium graminearum─the causative organism of the Fusarium head blight disease of wheat. The successful binding of dsRNA to GQDs-bPEIs was demonstrated through gel-shifting assays, showcasing the potential for efficient dsRNA delivery. We designed dsRNAs targeting the MGV1 and RAS1 genes of F. graminearum by using the pssRNAit pipeline, ensuring high specificity and no off-target effects. The coding sequences of the designed dsRAS1 and dsMGV1 were cloned into the L4440 vector and transformed into the Escherichia coli HT115 strain for dsRNA production. Fungal culture analysis revealed that the inclusion of dsRNAs in potato dextrose agar (PDA) media effectively slowed down the growth. Exogenous spraying experiments both in plate cultures and in intact wheat spikes demonstrated that the dsRNA:GQDs-bPEIs treatment was more effective in restricting fungal mycelium growth or the number of infected spikelets compared to naked dsRNA treatment. Our study demonstrates the promising potential of graphene quantum dots as carriers for dsRNA-based fungal disease management in wheat and other crops.

Dissecting the genetic basis of Fusarium crown rot resistance in wheat by genome wide association study

KEY MESSAGE

A locus conferring Fusarium crown rot resistance was identified on chromosome arm 3DL through genome wide association study and further validated in two recombinant inbred lines populations. Fusarium crown rot (FCR) is a severe soil borne disease in many wheat growing regions of the world. In this study, we attempted to detect loci conferring FCR resistance through a new seedling inoculation assay. A total of 223 wheat accessions from different geography origins were used to assemble an association panel for GWAS analysis. Four genotypes including Heng 4332, Luwanmai, Pingan 998 and Yannong 24 showed stable resistance to FCR. A total of 54 SNPs associated with FCR resistance were identified. Among the 10 putative QTLs represented by these SNPs, seven QTLs on chromosome 2B, 3A, 3D, 4A, 7A and 7B were novel and were consistently detected in at least two of the three trials conducted. Qfcr.cau.3D-3, which was targeted by 38 SNPs clustered within a genomic region of approximately 5.57 Mb (609.12-614.69 Mb) on chromosome arm 3DL, was consistently detected in all the three trials. The effects of Qfcr.cau.3D-3 were further validated in two recombinant inbred line populations. The presence of this locus reduced FCR severity up to 21.55%. Interestingly, the collinear positions of sequences containing the four SNPs associated with two FCR loci (Qfcr.cau.3A and Qfcr.cau.3B) were within the regions of Qfcr.cau.3D-3, suggesting that genes underlying these three loci may be homologous. Our results provide useful information for improving FCR resistance in wheat.

A Study of Soil-Borne Fusarium Wilt in Continuous Cropping Chrysanthemum Cultivar 'Guangyu' in Henan, China

Cut chrysanthemum, known as a highly favored floral choice globally, experiences a significant decline in production due to continuous cropping. The adverse physiological effects on cut chrysanthemums result from the degradation of a soil's physical and chemical properties, coupled with the proliferation of pathogens. The "Guangyu" cultivar in Xinxiang, Henan Province, China, has been specifically influenced by these effects. First, the precise pathogen accountable for wilt disease was effectively identified and validated in this study. An analysis was then conducted to examine the invasion pattern of the pathogen and the physiological response of chrysanthemum. Finally, the PacBio platform was employed to investigate the dynamic alterations in the microbial community within the soil rhizosphere by comparing the effects of 7 years of monocropping with the first year. Findings indicated that Fusarium solani was the primary causative agent responsible for wilt disease, because it possesses the ability to invade and establish colonies in plant roots, leading to alterations in various physiological parameters of plants. Continuous cropping significantly disturbed the microbial community composition, potentially acting as an additional influential factor in the advancement of wilt.

Fusarium spp. associated with Chenopodium quinoa crops in Colombia

Quinoa is a plant commonly-resistance to adverse biotic and abiotic factors. However, this crop can be affected by phytopathogenic fungi. There is a lack of knowledge about the fungi associated with quinoa plants in Colombia. Through morphological and molecular identification in this study were identified four Fusarium species associated with quinoa crops: Fusarium oxysporum, Fusarium graminearum, Fusarium equiseti, and Fusarium culmorum. For this, we collected samples of panicles, leaf tissue, root tissue, and soil for isolation of different isolates of Fusarium. We performed a pathogenicity test of the fungi strains, under greenhouse conditions to evaluate the pathogenicity in seedlings of the Piartal cultivar with two inoculation methods. First inoculating the stem through a nodal wound or second inoculating the abaxial face with a brush. The results indicate the presence of four species with both molecular markers, phylogenetically distributed in these groups. The four species turned out to be pathogenic but with different degrees of virulence with significant differences between F. graminearum and F. oxysporum depending on the inoculation method. This is the first report on the presence of Fusarium species isolated from Quinoa in Colombia.

An Improved Inoculation Method to Detect Wheat and Barley Genotypes for Resistance to Fusarium Crown Rot

Fusarium crown rot (FCR), caused by Fusarium species, is a serious soilborne fungal disease in many wheat growing regions in the world. A reliable FCR assessment method is essential for germplasm screening and host resistance studies. Here, we report a new assay in which we inoculated wheat seedlings grown in a glasshouse for FCR by injecting spore suspensions into the seedling stems. The effects of inoculum concentration and injection time points on disease severity were investigated. Of different treatments, the injection of 10⁷ macroconidia/ml suspension at one leaf and one heart stage gave best results. A collection of 92 emmer-derived hexaploid bread wheats, 43 barley germplasms, and four wheat genotypes with known resistance levels to FCR was used to validate this new method. Repeatability of the two trials in the validation experiments was high (r = 0.97, P < 0.01). Two emmer-derived hexaploid bread wheat and three Chinese barley germplasms showed consistent resistance to FCR in multiple rounds of selection. The short timeframe of this assay for phenotypic screening makes it a valuable tool to eliminate germplasms with undesirable susceptibility to FCR at seedling stage before costly field assays.