Identification of Pathogenic Fusarium spp. Responsible for Root Rot of Angelica sinensis and Characterization of their Biological Enemies in Dingxi, China

Root rot is a serious disease in plantations of A. sinensis, severely affecting yield and quality and threatening sustainable production. Fusarium isolates (n=32) were obtained from field samples of root rot tissue, leaves and infected soil. Isolates were identified by comparing the sequences of their internal transcribed spacer (ITS) region and translation elongation factor 1-ɑ (TEF-1ɑ) to sequences of known species in the NCBI-database. These Fusarium isolates include F. tricinctum (43.75%), F. equiseti (31.25%), F. solani (9.37%), F. oxysporum (6.25%), F. acuminatum (6.25%), and F. incarnatum (3.12%). For pathogenicity testing under greenhouse conditions, seven isolates were selected based on a phylogenetic analysis, including four strains of F. tricinctum and one strain each of F. solani, F. oxysporum, and F. acuminatum. The seven isolates were all pathogenic but differed in their ability to infect: the four F. tricinctum strains were capable pathogens causing root rot in A. sinensis at 100% incidence and the highly aggressive. Furthermore, the symptoms of root rot induced by those seven isolates were consistent with typical root rot cases in the field, but their disease severity varied. Observed histopathological preparations of F. tricinctum-infected seedlings and tissue-slides results showed this fungal species can penetrate epidermal cells and colonize the cortical cells where it induces necrosis and severe plasmolysis. Plate confrontation experiments showed that isolated rhizosphere bacteria inhibited the Fusarium pathogens that cause root rot in A. sinensis. Our results provide timely information for informing the use of biocontrol agents for suppression of root rot disease.

Some results of the study of alfalfa and meadow clover samples created by biotechnology methods

The conditions for creating alfalfa samples MN-2 (from the Selena variety) and P-67 (from the Lugovaya variety) with increased resistance to Fusarium pathogens using the method of gamete selection are described. The method is based on the selection of gametes in vivo under the influence of a selective factor (culture filtrate) introduced into the generative organs at the early stages of their development using vacuum infiltration. The method was developed in the biotechnology department of the V.N. V.R. Williams. The accessions are included in the breeding process and are currently the accessory varieties. In order to identify differences at the genetic level between the created varieties and the original forms, a comparative analysis was carried out using 2 types of molecular markers based on the PCR method. DNA polymorphism was detected using SRAP primers, which may indicate a change in the structure of genes associated with economic and biological traits. Research is ongoing. When growing under the conditions of a selection and greenhouse complex of acid-tolerant plants of meadow clover, created using cellular technologies in vitro, the infestation by powdery mildew of 120 acid-tolerant plants was studied. No signs of damage were found in 10% of plants. The largest number of affected plants (36.7%) had a score of 3. It was found that a high infestation with powdery mildew (scores 4 and 5) significantly reduces the number of inflorescences in the bush to 83.4 and 75.7%, respectively. Therefore, in further studies to create a population of acid-tolerant plants, the genotypes of meadow clover were used without signs and with a low score of powdery mildew damage.

Natural Products from Medicinal Plants against Phytopathogenic Fusarium Species: Current Research Endeavours, Challenges and Prospects

Many Fusarium species are pathogenic, causing crop diseases during crop production and spoilage of agricultural products in both commercial and smallholder farming. Fusarium attack often results into food contamination, yield loss and increases in food insecurity and food prices. Synthetic fungicides have been used as a control strategy for the management of crop diseases caused by Fusarium pathogens. The negative effects associated with application of many synthetic pesticides has necessitated the need to search for alternative control strategies that are affordable and environmentally safe. Research on medicinal plants as control agents for Fusarium pathogens has received attention since plants are readily available and they contain wide variety of secondary metabolites that are biodegradable. The activities of solvent extracts, essential oils and compounds from medicinal plants have been tested against Fusarium phytopathogenic species. A summary of recent information on antifungal activity of plants against Fusarium species is valuable for the development of biopesticides. This paper reviews the antifungal research conducted on medicinal plants against Fusarium pathogens, over a 10-year period, from January 2012 to May 2021. We also highlight the challenges and opportunities of using natural products from medicinal plants in crop protection. Several databases (Science Direct and Web of Science) were used to obtain information on botanical products used to control Fusarium diseases on crops. Keywords search used included natural products, antifungal, Fusarium, crops diseases, phytopathogenic, natural compounds and essential oil.

Metabolic Footprints of Burkholderia Sensu Lato Rhizosphere Bacteria Active against Maize Fusarium Pathogens

Consistent with their reported abundance in soils, several Burkholderia sensu lato strains were isolated from the rhizosphere of maize plants cultivated at different sites in central México. Comparative analysis of their 16S rRNA gene sequences permitted their separation into three distinctive clades, which were further subdivided into six other clusters by their close resemblance to (1) Trinickia dinghuensis; (2) Paraburkholderia kirstenboschensis, P. graminis, P. dilworthii and P. rhynchosiae; (3) B. gladioli; (4) B. arboris; (5) B. contaminans, or (6) B. metallica representative species. Direct confrontation assays revealed that these strains inhibited the growth of pathogenic Fusarium oxysporum f. sp. radicis-lycopersici, and F. verticillioides within a roughly 3–55% inhibition range. The use of a DIESI-based non-targeted mass spectroscopy experimental strategy further indicated that this method is an option for rapid determination of the pathogen inhibitory capacity of Burkholderia sensu lato strains based solely on the analysis of their exometabolome. Furthermore, it showed that the highest anti-fungal activity observed in B. contaminans and B. arboris was associated with a distinctive abundance of certain m/z ions, some of which were identified as components of the ornbactin and pyochelin siderophores. These results highlight the chemical diversity of Burkholderia sensu lato bacteria and suggest that their capacity to inhibit the Fusarium-related infection of maize in suppressive soils is associated with siderophore synthesis.

Antifungal Activity of Isolated Compounds from the Leaves of Combretum erythrophyllum (Burch.) Sond. and Withania somnifera (L.) Dunal against Fusarium Pathogens

Crop diseases caused by Fusarium pathogens, among other microorganisms, threaten crop production in both commercial and smallholder farming. There are increasing concerns about the use of conventional synthetic fungicides due to fungal resistance and the associated negative effects of these chemicals on human health, livestock and the environment. This leads to the search for alternative fungicides from nature, especially from plants. The objectives of this study were to characterize isolated compounds from Combretum erythrophyllum (Burch.) Sond. and Withania somnifera (L.) Dunal leaf extracts, evaluate their antifungal activity against Fusarium pathogens, their phytotoxicity on maize seed germination and their cytotoxicity effect on Raw 264.7 macrophage cells. The investigation led to the isolation of antifungal compounds characterized as 5-hydroxy-7,4′-dimethoxyflavone, maslinic acid (21-hydroxy-3-oxo-olean-12-en-28-oic acid) and withaferin A (4β,27-dihydroxy-1-oxo-5β,6β-epoxywitha-2-24-dienolide). The structural elucidation of the isolated compounds was established using nuclear magnetic resonance (NMR) spectroscopy, mass spectroscopy (MS) and, in comparison, with the available published data. These compounds showed good antifungal activity with minimum inhibitory concentrations (MIC) less than 1.0 mg/mL against one or more of the tested Fusarium pathogens (F. oxysporum, F. verticilloides, F. subglutinans, F. proliferatum, F. solani, F. graminearum, F. chlamydosporum and F. semitectum). The findings from this study indicate that medicinal plants are a good source of natural antifungals. Furthermore, the isolated antifungal compounds did not show any phytotoxic effects on maize seed germination. The toxicity of the compounds A (5-hydroxy-7,4′-dimethoxyflavone) and AI (4β,27-dihydroxy-1-oxo-5β,6β-epoxywitha-2-24-dienolide) was dose-dependent, while compound B (21-hydroxy-3-oxo-olean-12-en-28-oic acid) showed no toxicity effect against Raw 264.7 macrophage cells.

Fusarium root rot complex in soybean: Molecular characterization, trichothecene formation and cross-pathogenicity.

Soybean is threatened by many pathogens that negatively affect this crop's yield and quality, e.g., different Fusarium species that cause wilting and root rot diseases. Fusarium root rot (FRR) in soybean can be caused by F. graminearum and other Fusarium spp. that are associated with Fusarium head blight (FHB) in cereals. Therefore, it was important to enquire whether Fusarium pathogens from soybean can cause disease in wheat, and vice versa. Here, we investigated the Fusarium root rot complex in Manitoba (Canada) from symptomatic plants, using both culture- and molecular-based methods. We developed a molecular diagnostic toolkit to detect and differentiate between several Fusarium spp. involved in FHB and FRR, then we evaluated cross-pathogenicity of selected Fusarium isolates collected from soybean and wheat, and the results indicate that isolates recovered from one host can infect the other host. Trichothecene production by selected Fusarium spp. was also analyzed chemically using LC-MS in both soybean (root) and wheat (spike) tissues. Trichothecenes were also analyzed in soybean seeds from plants with FRR to check the potentiality of trichothecene translocation from infected roots to the seeds. All of the tested Fusarium isolates were capable of producing trichothecenes in wheat spikes and soybean roots, but no trichothecenes were detected in soybean seeds. This study provided evidence, for the first time, that trichothecenes were produced by several Fusarium spp. (F. cerealis, F. culmorum and F. sporotrichioides) during FRR development in soybean.

Potential Bacterial Antagonists from Cowshed Air for the Management of Fusarium Pathogens in Stored Rice

Rice is the principal staple food for more than half population of earth which is infested by many pathogens including Fusarium . Numbers of Fusarium species are responsible for causing pathogenic implications in rice like bakanae, rot, blight, etc. Majority of them produce mycotoxins which are responsible for human and animal toxicity and the cause of cancer disease. Adoption of biological control methods utilizing microbial antagonists might be an eco-friendly option. Bacterial species including Bacillus species have been isolated from various sources for utilisation as biocontrol agents to combat crop pathogens. Cow dung and the cow shed air have been a good source of such antagonistic bacteria. Hence, in the current study eighteen bacteria (BC1 to BC18) including Bacillus species have been isolated from cow shed air and paddy seeds stored in cowshed of Odisha, India. Bacteria isolated from domestic cowshed showed excellent inhibitory capacity than those of commercial cowshed against pathogenic Fusarium F90 and pathogenic as well as fumonisin producing Fusarium F55. Non-fumonisin producer Fusarium F90 was inhibited relatively with higher degree by all the antagonistic bacteria even it was completely suppressed by BC6 after three days of interaction. Paddy seeds stored in cowshed were found to be saturated with cowshed antagonistic bacteria. These bacterial antagonists hold potential to be utilized as Biological Control Agents (BCA) for safeguarding rice production. Investigation on more number of bacterial species from more cowsheds will definitely give more insights in the pattern and mode of inhibition.

Biological features and conditions of the surface cultivation of a strain-producer of microbiopreparation 11-3 Bacillus sp. – an antagonist of fusarium pathogens infecting oil flax

To develop a technological regimen of production of microbiopreparation in a preparative form ‘wettable powder’ (WP) we studied biological features and conditions of surface cultivation of the strainproducer 11-3 Bacillus sp. – an antagonist of fusariosis pathogen infecting oil flax. Cultural qualities of the strain-producer were studied in three agarized mediums. The optimal conditions for cultivation of the strain-producer on liquid nutrient mediums are estimated: temperature – 30–35 оС, рН – 8–10. As a source of carbon nutrition, glycerin and molasses can be used. Yeastrel and corn-steep concentrate are the optimal sources of nitrogen nutrition; the Tylon’s medium is optimal compound liquid nutrient medium for cultivation of the perspective bacterial strain 11-3 Bacillus sp. Optimal period of the surface cultivation of the bacterial strain 11-3 Bacillus sp. on the liquid nutrient Tylon’s medium was ten days, and a volume of sowing culture to nutrient medium – 2.0%.

Relationship between the Content of β-D-Glucans and Infection with Fusarium Pathogens in Oat (Avena sativa L.) Plants

In human nutrition, oats (Avena sativa L.) are mainly used for their dietary fiber, β-D-glucans and protein content. The content of β-D-glucans in oat grain is 2–7% and is influenced by genetic and/or environmental factors. High levels of this cell walls polysaccharide are observed in naked grains of cultivated oat. It the work, the relationship between the content of β-D-glucans in oat grain and the infection with Fusarium graminearum (FG) and Fusarium culmorum (FC) was analyzed. The hypothesis was that oats with higher content of β-D-glucans are better protected and the manifestation of artificial inoculation with Fusarium strains is weaker. In the 22 oat samples analyzed, the content of β-D-glucans was 0.71–5.06%. In controls, the average content was 2.15% for hulled and 3.25% for naked grains of cultivated oats. After the infection, a decrease was observed in all, naked, hulled and wild oats. As an evidence of lower rate of infection, statistically significant lower percentage of pathogen DNA (0.39%) and less deoxynivalenol (DON) mycotoxin (FC infection 10.66 mg/kg and FG 4.92 mg/kg) were observed in naked grains compared to hulled where the level of pathogen DNA was 2.09% and the average DON level was 21.95 mg/kg (FC) and 5.52 mg/kg (FG).