Epidemiological Studies of Pan-Azole Resistant Aspergillus fumigatus Populations Sampled during Tulip Cultivation Show Clonal Expansion with Acquisition of Multi-Fungicide Resistance as Potential Driver

Pan-azole resistant isolates are found in clinical and environmental Aspergillus fumigatus (Af) populations. Azole resistance can evolve in both settings, with Af directly targeted by antifungals in patients and, in the environment, Af unintendedly exposed to fungicides used for material preservation and plant disease control. Resistance to non-azole fungicides, including methyl benzimidazole carbamates (MBCs), quinone outside inhibitors (QoIs) and succinate dehydrogenase inhibitors (SDHIs), has recently been reported. These fungicide groups are not used in medicine but can play an important role in the further spread of pan-azole resistant genotypes. We investigated the multi-fungicide resistance status and the genetic diversity of Af populations sampled from tulip field soils, tulip peel waste and flower compost heaps using fungicide sensitivity testing and a range of genotyping tools, including STRAf typing and sequencing of fungicide resistant alleles. Two major clones were present in the tulip bulb population. Comparisons with clinical isolates and literature data revealed that several common clonal lineages of TR34/L98H and TR46/Y121F/T289A strains that have expanded successfully in the environment have also acquired resistance to MBC, QoI and/or SDHI fungicides. Strains carrying multiple fungicide resistant alleles have a competitive advantage in environments where residues of multiple fungicides belonging to different modes of action are present.

Biological Control of Plant Diseases in Changing Environment

Excessive pesticide application for plant disease control can result in environmental and health-related problems [...]

Synthetic Oligopeptides Derived from γ-Core Regions of Tomato Cysteine-Rich Peptides Possess Antimicrobial Activity against Human and Plant Pathogens

Plant cysteine-rich peptides (CRPs) represent a diverse group of molecules involved in different aspects of plant physiology. Antimicrobial peptides, which directly suppress the growth of pathogens, are regarded as promising templates for the development of next-generation pharmaceuticals and ecologically friendly plant disease control agents. Their oligopeptide fragments are even more promising because of their low production costs. The goal of this work was to explore the antimicrobial activity of nine short peptides derived from the γ-core-containing regions of tomato CRPs against important plant and human pathogens. We discovered antimicrobial activity in peptides derived from the defensin-like peptides, snakins, and MEG, which demonstrates the direct involvement of these CRPs in defense reactions in tomato. The CRP-derived short peptides appeared particularly active against the gram-positive bacterium Clavibacter michiganensis, which causes bacterial wilt—opening up new possibilities for their use in agriculture to control this dangerous disease. Furthermore, high inhibitory potency of short oligopeptides was demonstrated against the yeast Cryptococcus neoformans, which causes serious diseases in humans, making these peptide molecules promising candidates for the development of next-generation pharmaceuticals. Studies of the mode of action of the two most active peptides indicate fungal membrane permeabilization as a mechanism of antimicrobial action.

Fusarium Oxysporum Disrupts Microbiome-Metabolome Networks in Arabidopsis Thaliana Roots

BackgroundAlthough it is well established that plant metabolomes mediate microbiome assembly, the question of how metabolome-microbiome interactions may prevent pathogen invasion remains to be answered. To address this question, we studied microbiome and metabolome profiles of two Arabidopsis thaliana accessions, Columbia-0 (Col-0) and Landsberg erecta (Ler-0) with differential resistance profiles to the fungal pathogen Fusarium oxysporum f.sp. mathioli (FOM). We used amplicon sequencing to characterize bacterial (16S) and fungal (ITS2) communities, and we used targeted metabolite analysis across 5 stages of FOM host progression. ResultsWe found that microbiome and metabolome profiles were markedly altered in FOM-inoculated and non-inoculated samples of resistant Col-0 and susceptible Ler-0. Co-occurrence network analysis revealed robust microbial networks in the resistant Col-0 compared to the susceptible Ler-0, during FOM infection. Specific metabolites and microbial OTUs (including indicator and hub OTUs) correlated in both non-inoculated and inoculated Col-0 and Ler-0. The glucosinolates 4-hydroxyglucobrassicin, neoglucobrassicin and indole-3 carbinol, but also phenolic compounds were active in structuring the A. thaliana-microbiome. ConclusionsOur results highlight the interactive effects of host resistance and its associated microbiota on Fusarium infection and progression. These findings shed significant insights into plant inter-omics dynamics during pathogen invasion and could possibly facilitate the exploitation of microbiomes for plant disease control.

Chaetomium Application in Agriculture

Chaetomium species for plant disease control are reported to be antagonize many plant pathogens. It is a new broad spectrum biological fungicide from Chaetomium species which firstly discovered and patented No. 6266, International Code: AO 1 N 25/12, and registered as Ketomium® mycofungicide for plant disease control in Thailand, Laos, Vietnam, Cambodia and China. Chaetoimum biofungicide and biostimulants are applied to implement integrated plant disease control. It showed protective and curative effects in controlling plant disease and promoting plant growth. It has been successfully applied to the infested soils with integrated cultural control for the long-term protection against rice blast (Magnaporte oryzae), durian and black Pepper rot (Piper nigram L.) (Phytophthora palmivora), citrus rot (Phytophthora parasitica) and strawberry rot (Fragaria spp.) caused by Phytophthora cactorum, wilt of tomato (Fusarium oxysporum f. sp. lycopersici), basal rot of corn (Sclerotium rolfsii) and anthracnose (Colletotrichum spp.) etc. Further research is reported on the other bioactive compounds from active strains of Chaetomium spp. We have discovered various new compounds from Ch. globosum, Ch. cupreum, Ch. elatum, Ch. cochliodes, Ch. brasiliense, Ch. lucknowense, Ch. longirostre and Ch. siamense. These new compounds are not only inhibiting human pathogens (anti-malaria, anti-tuberculosis, anti-cancer cell lines and anti-C. albicans etc) but also plant pathogens as well. These active natural products from different strains of Chaetomium spp. are further developed to be biodegradable nanoparticles from active metabolites as a new discovery of scientific investigation which used to induce plant immunity, namely microbial degradable nano-elicitors for inducing immunity through phytoalexin production in plants e.g. inducing tomato to produce alpha-tomaline against Fusarium wilt of tomato, capsidiol against chili anthracnose, sakuranitin and oryzalexin B against rice blast, scopletin and anthrocyaidin against Phytophthora or Pythium rot Durian and scoparone against Phytophthora or Pythium rot of citrus. Chaetomium biofungicide can be applied instead of toxic chemical fungicides to control plant diseases.

Effect of pyrolysis temperature on Si release of alkali-enhanced Si-rich biochar and plant response

Recent studies have shown that silicon (Si) dissolution from biochar may be influenced by the pyrolysis temperature. In addition, the enhancement of biochar by treatment with alkali has been proposed to produce a Si source that can be used for environmentally friendly plant disease control. In this study, biochars from rice straw and rice husk pretreated with KOH, CaO and K2CO3 and then pyrolyzed at 350, 450 and 550 °C were prepared to evaluate the effects of pyrolysis temperature on Si release and plant uptake from alkali-enhanced Si-rich biochar. Extractable Si and dissolution Si from the prepared biochars were assessed by different short-term chemical methods and long-term (30-day) release in dilute acid and neutral salt solutions, respectively, along with a rice potting experiment in greenhouse. For both rice straw- and husk-derived alkali-enhanced biochars (RS-10KB and HS-10K2B, respectively), increasing the pyrolysis temperature from 350 to 550 °C generally had the highest extractable Si and increased Si content extracted by 5-day sodium carbonate and ammonium nitrate (5dSCAN) designated for fertilizer Si by 61–142%, whereas non-enhanced biochars had more extractable Si at 350 °C. The alkali-enhanced biochars produced at 550 °C pyrolysis temperature also released 82–172% and 27–79% more Si than that of 350 °C produced biochar in unbuffered weak acid and neutral salt solutions, respectively, over 30 days. In addition, alkali-enhanced biochars, especially that derived from rice husk at 550 °C facilitated 6–21% greater Si uptake by rice and 44–101% higher rice grain yields than lower temperature biochars, non-enhanced biochars, or conventional Si fertilizers (wollastonite and silicate calcium slag). Overall, this study demonstrated that 550 °C is more efficient than lower pyrolysis temperature for preparing alkali-enhanced biochar to improve Si release for plant growth.

Plant Disease Control Efficacy of Platycladus orientalis and Its Antifungal Compounds

Plants contain a number of bioactive compounds that exhibit antimicrobial activity, which can be recognized as an important source of agrochemicals for plant disease control. In searching for natural alternatives to synthetic fungicides, we found that a methanol extract of the plant species Platycladus orientalis suppressed the disease development of rice blast caused by Magnaporthe oryzae. Through a series of chromatography procedures in combination with activity-guided fractionation, we isolated and identified a total of eleven compounds including four labdane-type diterpenes (1–4), six isopimarane-type diterpenes (5–10), and one sesquiterpene (11). Of the identified compounds, the MIC values of compounds 1, 2, 5 & 6 mixture, 9, and 11 ranged from 100 to 200 μg/mL against M. oryzae, whereas the other compounds were over 200 μg/mL. When rice plants were treated with the antifungal compounds, compounds 1, 2, and 9 effectively suppressed the development of rice blast at all concentrations tested by over 75% compared to the non-treatment control. In addition, a mixture of compounds 5 & 6 that constituted 66% of the P. orientalis ethyl acetate fraction also exhibited a moderate disease control efficacy. Together, our data suggest that the methanol extract of P. orientalis including terpenoid compounds has potential as a crop protection agent.

Gases Released During Soil Biodisinfestation of Pepper Greenhouses Reduce Survival of Phytophthora capsici Oospores in Northern Spain

Phytophthora capsici is one of the oomycetes that affects protected pepper crops in different agroclimatic areas of Spain. Currently, environmentally friendly strategies such as biodisinfestation for plant disease control have become increasingly popular. In this study, the effect of released gases during biodisinfestation with a fresh manures mixture amendment on P. capsici oospore viability was determined. A biodisinfestation trial was performed in a greenhouse located in northern Spain (Biscay), with a mixture of fresh sheep (2 kg m−2) and dry poultry manures (0.5 kg m−2) followed by soil sealing with a transparent polyethylene plastic film for 21 days (onset June 15th). Gases were sampled from the aerial cavity of biodisinfested plots at different days after soil sealing (0–1–2–3–4–7–9–11, and 14 days). Vacutainer tubes were incubated at 20°C with oospores of P. capsici that were previously placed under vacuum and refilled with extracted gases. Treatments assayed were gases from different sampling times (0–1–2–3–4–7–9–11–14 days, and succession of days 1–2–3–4–7–9–11–14) combined with different exposure times (7–14–21 days) at 20°C in the laboratory. Control treatments were included: air-tubes and vacuum-tubes. An additional reference treatment under real field conditions was also considered: buried oospores at 15 cm depth in the biodisinfested plots. Oospore viability was determined with the plasmolysis method. The most effective treatment was the succession of gases collected during all sampling days. The significant but slight reduction in oospore viability by exposure to the different gas treatments was consistent with the low dose of applied amendment and the low soil temperature registered at 15 cm depth during soil biodisinfestation (>25°C−100% time, >35°C−23%, >40°C−3%). The above circumstances might have generated a small quantity of gases with low impact on oospore viability. The biodisinfested soil at 15 cm depth reference treatment showed the lowest oospore viability in all the exposure times assayed. The overlap of thermal and higher biofumigation effects in this treatment could likely be responsible for its greater efficacy. A disinfectant effect purely attributable to released gases throughout biodisinfestation has been demonstrated. We believe that our research will serve as a base for future application in agro-environments with reduced thermal inactivation effects.

Punica granatum L. extract contributes to phytopathogens control and enhances Eruca vesicaria (L.) Cav. germination in vitro and in vivo

The study aimed to investigate antimicrobial activity of the hydroalcoholic crude extract from the fruit peel of Punica granatum (Pp) and punicalagin compound (Pg) on phytopathogenic bacterial isolates and its potential use as a sustainable alternative in treatment of vegetable seeds. The antimicrobial activity in vitro was tested by agar well diffusion assay and through viability tests in liquid medium. In vivo treatment with Pp was tested on Eruca vesicaria seeds infected with Xanthomonas campestris pv. campestris. Pp induced the formation of large inhibition zones to the growth of the tested pathogens (35.33 mm – 6.66 mm), with dose-dependent effect. Viability tests confirmed the antimicrobial activity of the Pp on X. campestris pv. campestris and P. carotovorum subsp. carotovorum with minimum inhibitory concentration (MIC) of 125 μg/mL. Punicalagin compound presented MIC of the 31.25 μg/mL. The seed treatment with Pp indicated control of pathogen-induced symptoms in seedlings of the E. vesicaria and positive effect in seed germination, emergence and in stomatal functionality. The results indicate strong potential of the extract from the fruit peel of P. granatum and Punicalagin for formulating botanical pesticides for plant disease control.