The elemental defense effect of cadmium on Alternaria brassicicola in Brassica juncea

Background The elemental defense hypothesis states a new defensive strategy that hyperaccumulators defense against herbivores or pathogens attacks by accumulating heavy metals. Brassica juncea has an excellent ability of cadmium (Cd) accumulation. However, the elemental defense effect and its regulation mechanism in B. juncea remain unclear. Results In this study, we profiled the elemental defense effect and the molecular regulatory mechanism in Cd-accumulated B. juncea after Alternaria brassicicola infection. B. juncea treated with 180 mg Kg− 1 DW CdCl2 2.5H2O exhibited obvious elemental defense effect after 72 h of infection with A. brassicicola. The expression of some defense-related genes including BjNPR1, BjPR12, BjPR2, and stress-related miRNAs (miR156, miR397, miR398a, miR398b/c, miR408, miR395a, miR395b, miR396a, and miR396b) were remarkably elevated during elemental defense in B. juncea. Conclusions The results indicate that Cd-accumulated B. juncea may defend against pathogens by coordinating salicylic acid (SA) and jasmonic acid (JA) mediated systemic acquired resistance (SAR) and elemental defense in a synergistic joint effect. Furthermore, the expression of miRNAs related to heavy metal stress response and disease resistance may regulate the balance between pathogen defense and heavy metal stress-responsive in B. juncea. The findings provide experimental evidence for the elemental defense hypothesis in plants from the perspectives of phytohormones, defense-related genes, and miRNAs.

Phytopathological and nutraceutical evaluation of cauliflower plants treated with high dilutions of arsenic trioxide

Introduction: This research aimed at verifying the effects of highly diluted (HD) treatments on cauliflower (Brassica oleracea L.) plants both healthy and inoculated by the fungus Alternaria brassicicola, causing the dark leaf spot disease. In vitro spore germination assays (A), growth chamber experiments (B) and field trials (C) were performed. Material and Methods: (A): spore suspensions were prepared in HD treatments and their inhibiting effect on germination was recorded microscopically after incubation at 25°C for 5 h. (B): the same treatments were tested in plants artificially inoculated with the fungus. The infection level on leaves was blindly evaluated by a previously defined infection scale. (C): the field was divided into plots according to a complete randomized block design. In the first trial (i), plants were artificially inoculated and weekly treated; the infection level was evaluated on cauliflower heads. The second trial (ii) was performed on the same field with the aim to induce a natural infection, mediated by infected crop residues. Measurement endpoints concerned the evaluation of some physiological parameters along with the glucosinolate content on cauliflower heads. Results: (A): arsenic trioxide (As 35x and 35x diluted 1:5000) and Cuprum 5x induced highly significant inhibition of germination rate (-60%) vs. control. (B): As 35x and Cu 3 g/l induced a significant decrease of mean infection level (-50%). (C): in (i), a significant reduction of disease symptoms on heads was recorded for As 35x and Cu 3 g/l (-45%). In (ii) natural fungal infection did not occur due to dry weather conditions; physiological and nutraceutical analyses of healthy heads demonstrated that As 35x induced a significant increase of both head size and glucosinolate content. Discussion: Some evidences on the efficacy of arsenic, at different decimal and centesimal HD, in fungal and viral disease control were previously reported [1]. In the present study the efficacy of HD arsenic in dark leaf spot control in field has been shown for the first time: since fungal inoculation was performed on the leaves before flowering, we can hypothesize that this treatment induced an increase of plant resistance to fungal infection. Conclusions: This research showed the possibility of using HD arsenic in agriculture (“agrohomeopathy”), as it increased both plant resistance to fungal infection and the content of glucosinolates, ie secondary metabolites involved in plant resistance mechanisms [2] and considered as “plant food protection agents” [3]. Acknowledgments: Authors declare there is no conflict of interest. This research has been supported by Marche Region. A grateful acknowledgement to Dr. Leonardo Valenti for his support to this research. The authors thank Laboratoires Boiron srl for the grant awarded to one of the author Dr. Grazia Trebbi. Finally, authors are grateful to Cemon srl for financial support of glucosinolate analyses. We had full access to all the data in this study and we take responsibility for the integrity of the data and the accuracy of the data analysis Keywords: cauliflower, arsenic trioxide, Alternaria brassicicola, glucosinolates References [1] Betti L, Trebbi G, Majewsky V, Scherr C, Shah-Rossi D, Jäger T, et al. Use of homeopathic preparations in phytopathological models and in field trials: a critical review. Homeopathy 2009; 98: 244-266. [2] Ménard R, Larue J-P, Silué D, Thouvenot D. Glucosinolates in cauliflower as biochemical markers for resistance against downy mildew. Phytochemistry 1999; 52: 29-35. [3] Talalay P, Fahey JW. Phytochemicals from Cruciferous plants protect against cancer by modulating carcinogen metabolism. J Nutr. 2001; 131:3027S- 3033S.

Assessment of the antifungal activity of the violacein-forming strain Janthinobacterium sp. B-3515 against the mould fungus Alternaria brassicicola F-1864

A study of antifungal properties of violacein-forming strain Janthinobacterium sp. B-3515 as well as its secondary metabolite, violacein, against Alternaria brassicicola F-1864 is presented. Regardless of the presence of bacteria, mycelium growth in the first two days proceeded at the same rate. The effect of the bacterial strain was manifested after the third day of incubation. In general, during co-culture, the bacterial strain statistically significantly reduced the average growth of the mycelium of the mould fungus by 10%. The average growth of A. brassicicola F-1864 was decreased in the presence of an aqueous solution of violacein in the nutrient medium (1%, 3%, and 5%). The pigment in 5% concentration had the greatest effect, as the difference between the average growth of the control group and the experimental group was 18%. The mycostatic activity of bacteria of genus Janthinobacterium and violacein against mould fungus Alternaria brassicicola F-1864 was shown for the first time.

Morphological and Molecular Identification of Fungi Causing Canker Disease on Melia Azidarch Trees in Some Regions of Mosul Provinces, Iraq

The aim of this study was to identify the fungi associated with canker disease on Melia azidarch trees inside Mosul University campus and the presidential palaces regions in Mosul Province, Iraq. Results of isolation showed the presenting of the fungi (Nattrassia mangiferae, Neoscylitidium dimidiatum Penz., Fusarium graminearium Schw., Alternaria brassicicola Schw., Aspergillus sp. and Penecillium sp.), which accompanied with the samples displayed cankering symptoms during the period from April to December/2020, the maximum of dominance was 85% for the fungus Neoscylitidium dimidiatum in August, while the lowest was 49% in April for the same year, followed by Fusarium graminearium with 38% in December, while the lowest percentage was 4% in October, then Alternaria brassicicola Schw. was 25% in April and the lowest value was 0% in August, followed by Aspergillus sp. and Penecillium sp. with low isolation percentages the maximum of which 25% and the lowest is 0% in August. When studying the pathogenicity of the isolated fungi, the results showed a high pathogenic effect in terms the length, diameter and the area of cankers symptom. Based on the results of the molecular diagnosis, the morphological identification was confirmed and it was clear that Fusarium austroamericanum, detection is considered the first record of this fungus in Iraq Melia azidarch trees.

Longevity of Plant Pathogens in Dry Agricultural Seeds During 30 Years of Storage

Plant diseases may survive and be spread by infected seeds. In this study we monitored the longevity of 14 seed-borne pathogens in 9 crop species commonly grown in the Nordic countries, in addition to a sample of sclerotia of Sclerotinia sclerotiorum. The data from the first 30 years of a 100-year seed storage experiment located in a natural −3.5 °C environment (permafrost) in Svalbard, Norway, are presented. To date, the pathogens, tested by traditional seed health testing methods (freezing blotter, agar plates, growing on tests), have survived. Linear regression analyses showed that the seed infection percentages of Drechslera dictyoides in meadow fescue, Drechslera phlei in timothy, and Septoria nodorum in wheat were significantly reduced compared to the percentages at the start of the experiment (from 63% to 34%, from 70% to 65%, and from 15% to 1%, respectively), and that Phoma betae in beet had increased significantly (from 43% to 56%). No trends in the infection percentage were observed over the years in Drechslera spp. in barley (fluctuating between 30% and 64%) or in Alternaria brassicicola in cabbage (fluctuating between 82% and 99%), nor in pathogens with low seed infection percentages at the start of the experiment. A major part of the stored sclerotia was viable after 30 years. To avoid the spread of seed-borne diseases, it is recommended that gene banks implement routines that avoid the use of infected seeds.