Quantification of Trichoderma afroharzianum, Trichoderma harzianum and Trichoderma gamsii inoculants in soil, the wheat rhizosphere and in planta suppression of the crown rot pathogen Fusarium pseudograminearum

Wheat rhizosphere dynamics of Trichoderma gamsii A5MH and suppression of a Pythium root rot-Fusarium crown rot disease complex over two consecutive cropping seasons

AIMS

Determine the wheat rhizosphere competence of Trichoderma gamsii strain A5MH and in planta suppression of the Pythium root and Fusarium crown rot pathogens Globisporangium irregulare and Fusarium pseudograminearum.

METHODS AND RESULTS

Wheat was continuously cropped (eight years) at a minimum tillage, low growing season rainfall (GSR ≤ 170 mm) site shown as highly conducive to Pythium root and Fusarium crown rots. Root isolation frequency (RIF) and qPCR were used to determine the rhizosphere dynamics of strain A5MH and the target pathogens at tillering, grain harvest, and in postharvest stubble over the final 2 years. Strain A5MH actively colonized the wheat rhizosphere throughout both growing seasons, had high root abundance at harvest [log 4.5 genome copies (GC) g-1] and persisted in standing stubble for at least 293-d postinoculation. Globisporangium irregulare was most abundant in roots at tillering, whereas F. pseudograminearum was only abundant at harvest and up to 9-fold greater in the drier, second year (GSR 105 mm). Strain A5MH decreased RIF of both pathogens by up to 40%, root abundance of G. irregulare by 100-fold, and F. pseudogaminearum by 700-fold, but was ineffective against crown rot in the second year when pathogen abundance was >log 6.0 GC g-1 root. Strain A5MH increased crop emergence and tillering biomass by up to 40%.

CONCLUSIONS

Further trials are required to determine if the A5MH-induced pathogen suppression translates to yield improvements in higher rainfall regions where non-cereal rotations reduce crown rot inoculum.

Effects of farmland abandonment on anthropogenic-alluvial soil microbiota and contaminant residues in Lycium barbarum fields

AIMS

There has been an increasing tendency to abandon crop cultivation and farming in old Lycium barbarum (wolfberry) stands to allow for natural restoration. However, little research has been dedicated to deciphering how soil quality changes in L. barbarum fields following abandonment from a physicochemical and microbiological perspective. Here we assessed the effects of farmland abandonment on anthropogenic-alluvial soil microbiota and contaminant residues in L. barbarum fields in Ningxia, China.

METHODS AND RESULTS

Soil microbiota, heavy metal, and neonicotinoid pesticide profiles in L. barbarum fields abandoned for one to four years were characterized. Microbial community analysis was performed by high-throughput sequencing of the bacterial 16S ribosomal RNA genes and the fungal nuclear ribosomal internal transcribed spacer region. Soil bacterial diversity increased from before abandonment to year three after abandonment, and fungal diversity peaked in year one after abandonment. Enrichment of potentially beneficial taxa (e.g. Limnobacter, Cavicella) as well as pathogenic taxa (e.g. Ilyonectria) was observed in the abandoned field soils, along with depletion of other taxa (e.g. Planococcus, Bipolaris). Soil copper, zinc, cadmium, imidacloprid, and acetamiprid concentrations all decreased with increasing time since abandonment and had varied correlations with soil quality, microbial diversity, and the relative abundances of major phyla. Soil available phosphorus, nitrate-nitrogen, and pH were the key factors shaping bacterial communities. The structuring of fungal communities was strongly influenced by soil pH, available phosphorus, and available nitrogen contents.

CONCLUSIONS

There were positive consequences of farmland abandonment in L. barbarum fields, such as optimized microbial community structure, reduced heavy metal accumulation, and enhanced pesticide degradation.

Assessment of Tunisian Trichoderma Isolates on Wheat Seed Germination, Seedling Growth and Fusarium Seedling Blight Suppression

Beneficial microorganisms, including members of the Trichoderma genus, are known for their ability to promote plant growth and disease resistance, as well as being alternatives to synthetic inputs in agriculture. In this study, 111 Trichoderma strains were isolated from the rhizospheric soil of Florence Aurore, an ancient wheat variety that was cultivated in an organic farming system in Tunisia. A preliminary ITS analysis allowed us to cluster these 111 isolates into three main groups, T. harzianum (74 isolates), T. lixii (16 isolates) and T. sp. (21 isolates), represented by six different species. Their multi-locus analysis (tef1, translation elongation factor 1; rpb2, RNA polymerase B) identified three T. afroharzianum, one T. lixii, one T. atrobrunneum and one T. lentinulae species. These six new strains were selected to determine their suitability as plant growth promoters (PGP) and biocontrol agents (BCA) against Fusarium seedling blight disease (FSB) in wheat caused by Fusarium culmorum. All of the strains exhibited PGP abilities correlated to ammonia and indole-like compound production. In terms of biocontrol activity, all of the strains inhibited the development of F. culmorum in vitro, which is linked to the production of lytic enzymes, as well as diffusible and volatile organic compounds. An in planta assay was carried out on the seeds of a Tunisian modern wheat variety (Khiar) by coating them with Trichoderma. A significant increase in biomass was observed, which is associated with increased chlorophyll and nitrogen. An FSB bioprotective effect was confirmed for all strains (with Th01 being the most effective) by suppressing morbid symptoms in germinated seeds and seedlings, as well as by limiting F. culmorum aggressiveness on overall plant growth. Plant transcriptome analysis revealed that the isolates triggered several SA- and JA-dependent defense-encoding genes involved in F. culmorum resistance in the roots and leaves of three-week-old seedlings. This finding makes these strains very promising in promoting growth and controlling FSB disease in modern wheat varieties.

Trichoderma Species: Our Best Fungal Allies in the Biocontrol of Plant Diseases-A Review

Biocontrol agents (BCA) have been an important tool in agriculture to prevent crop losses due to plant pathogens infections and to increase plant food production globally, diminishing the necessity for chemical pesticides and fertilizers and offering a more sustainable and environmentally friendly option. Fungi from the genus Trichoderma are among the most used and studied microorganisms as BCA due to the variety of biocontrol traits, such as parasitism, antibiosis, secondary metabolites (SM) production, and plant defense system induction. Several Trichoderma species are well-known mycoparasites. However, some of those species can antagonize other organisms such as nematodes and plant pests, making this fungus a very versatile BCA. Trichoderma has been used in agriculture as part of innovative bioformulations, either just Trichoderma species or in combination with other plant-beneficial microbes, such as plant growth-promoting bacteria (PGPB). Here, we review the most recent literature regarding the biocontrol studies about six of the most used Trichoderma species, T. atroviride, T. harzianum, T. asperellum, T. virens, T. longibrachiatum, and T. viride, highlighting their biocontrol traits and the use of these fungal genera in Trichoderma-based formulations to control or prevent plant diseases, and their importance as a substitute for chemical pesticides and fertilizers.

Identification of beneficial Lebanese Trichoderma spp. wheat endophytes

Wheat is one of the most important crops in the world. Its production can be influenced by a diversity of beneficial and pathogenic rhizospheric microbes, including fungi. Amongst them, beneficial Trichoderma spp. can be used as alternatives to chemical fertilizers, as they are cheap and harmless to the environment. Our study aimed to isolate, identify, and characterize Trichoderma spp. from Lebanon associated with wheat. Two Trichoderma strains belonging to T. afroharzianum, and T. guizhouense species, were isolated and found to be endophytes, enhancing root growth and producing Indole-3-acetic acid. Inoculation also improved seedling development, and increased plant growth and yield. Furthermore, the two strains inhibit Fusarium growth in vitro. These Trichoderma spp. have thus the capacity to be used as organic fertilizers for wheat.

Trichoderma atroviride seed dressing influenced the fungal community and pathogenic fungi in the wheat rhizosphere

Fusarium crown rot and wheat sharp eyespot are major soil-borne diseases of wheat, causing serious losses to wheat yield in China. We applied high-throughput sequencing combined with qPCR to determine the effect of winter wheat seed dressing, with either Trichoderma atroviride HB20111 spore suspension or a chemical fungicide consisting of 6% tebuconazole, on the fungal community composition and absolute content of pathogens Fusarium pseudograminearum and Rhizoctonia cerealis in the rhizosphere at 180 days after planting. The results showed that the Trichoderma and chemical fungicide significantly reduced the amount of F. pseudograminearum in the rhizosphere soil (p < 0.05), and also changed the composition and structure of the fungal community. In addition, field disease investigation and yield measurement showed that T. atroviride HB20111 treatment reduced the whiteheads with an average control effect of 60.1%, 14.9% higher than the chemical treatment; T. atroviride HB20111 increased yield by 7.7%, which was slightly more than the chemical treatment. Therefore, T. atroviride HB20111 was found to have the potential to replace chemical fungicides to control an extended range of soil-borne diseases of wheat and to improve wheat yield.

Impact of ozonated water disinfestation on soil fungal community composition in continuous ginger field

This study aimed to explore the impact of ozonated water (OW) disinfestation on soil fungal community composition in continuous ginger field. All soil samples were collected in continuous ginger field. There were two groups and 5 time points (0, 1, 3, 5, 9 day) in our study, including OW disinfestation treatment group (O3 group) and control group (CK group). Via internal transcribed spacer (ITS) sequencing and further analysis, the changes of fungal community composition were determined. As a result, at 0 and 9 days after aeration, the operational taxonomic units (OTUs) in O3 group were significantly higher than that in CK group. Compared with the CK group, in O3 group: the ACE and Chao1 index significantly increased on day 1, and the Shannon index significantly decreased while Simpson index significantly increased on day 0 after aeration. In O3 group, there were dynamic changes of top 10 abundance fungi from the genus-level and the growth of Trichoderma and Rhodotorula had been promoted while Hannaella was inhibited. In conclusion, OW disinfestation had complicated impacts on fungal communities in continuous ginger fields. The growth of Trichoderma and Rhodotorula has been promoted during disinfestation, which provided more reference information for soil OW disinfestation research.

Difference responses of soil fungal communities to cattle and chicken manure composting application

AIMS

Cattle and poultry manure composting are often applied on agricultural lands but the fungal community composition before and after application in soils is still unclear. Describe soil fungal diversity after manure applications contribute to the correct resource use of livestock and poultry manures.

METHODS AND RESULTS

Fresh manure samples were obtained from 10 beef cow farms and 12 egg-laying poultry farms at five distinct phases of rearing. Surface soil samples were collected from vegetable plots within the farms after manure application at 15, 30 and 45 t hm^-2 . Using high-throughput sequencing techniques, the ITS region was utilized to describe soil fungus populations. The fungal OTUs, Chao1 and ACE of cattle manure were relative higher in fattening stage (>12 months), the OTUs and ACE of chicken manure were the highest in the initial laying stage (16-24 weeks). The fungal diversity indices of vegetable soils hadn't linear change after cow or chicken manure application compared with the control. Ascomycota (84.7% of total sequences), Neocallimastigomycota (9.69%), and Basidiomycota (4.6%) were the dominant phyla in cattle manure. Ascomycota (88.9%) also predominated in chicken manure, followed by Basidiomycota (8.9%). Following both cattle and chicken manure application, the abundance of Ascomycota decreased, while Basidiomycota and Chytridiomycota increased in the soils. None of the dominant genus increased or decreased linearly with the increase of cattle and chicken composting application rate. The fungal dominant genera of the soils with and without manure composting application were mostly affected by soil pH and EC than manure. Pearson's correlation analysis revealed that organic matter, Cu and Hg contents were strongly linked to the fungal diversity and the abundance of specific taxa in cattle manure. In chicken manure, OM, TN and Zn were major factors controlling the fungal diversity and community composition. Soil pH, EC, and Cu, Zn, Cd, Hg and As content had pronounced effects on beneficial and pathogenic genus in soil with and without manure composting. Beneficial fungal genus such as Aspergillus, Plectosphaerella, Acremonium, Meyerozyma and fungal pathogenic like Fusarium, Cladosporium, Verticillium were sensitive to properties (EC, pH, OM) and heavy metals (Cu, Zn, Hg) contents of environment, relatively. The study can serve as an applicable contribution helping in farms management (especially to cattle and poultry breeding) and improve their resource use of livestock and poultry manure.

CONCLUSIONS

Soil heterogeneity rather than manure determines fungal communities in the vegetable fields, but we can encourage the sensible use of cattle and chicken manure in agroecosystems.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study will help the farmers regulate the dosage of feed components which can increase the number of beneficial fungal genus or reduce the number of pathogenic fungal genus, improve their resource use of livestock and poultry manure, and encourage the sensible use of cattle and chicken manure in agroecosystems.

Developing Actinobacterial Endophytes as Biocontrol Products for Fusarium pseudograminearum in Wheat

Crown rot of wheat, caused by Fusarium pseudograminearum, results in millions of dollars of yield losses globally each year. Management strategies to control crown rot are limited and there are concerns about development of fungicide resistance so novel treatment strategies are desirable. A collection of endophytic Actinobacteria was screened for their ability to suppress the growth of F. pseudograminearum and the development of crown rot symptoms in wheat with the aim of identifying candidates that can be developed into biocontrol products. The ability of the Actinobacteria isolates to suppress the growth of three different F. pseudograminearum strains in vitro was assessed using agar-plate competition assays. Soil-free seedling assays were used to screen for suppression of development of early disease symptoms in the susceptible wheat (Triticum aestivum) cv. Tamaroi. Four of the isolates were tested in a glasshouse pot experiment to assess their ability to decrease disease symptoms and prevent yield losses in wheat cv. Tamaroi grown to maturity in an unsterilized soil. The screening of 53 isolates identified two Streptomyces isolates, MH71 and MH243, with very strong antifungal activity against F. pseudograminearum strains in agar-plate competition and seedling assays. In the glasshouse pot trial, plants treated with seed coatings of either MH71 or MH243 had > 24% lower disease severity than control plants infected with F. pseudograminearum. These two cultures show potential for development as biocontrol products because they are easy to culture, grow on relatively inexpensive media, produce highly durable spores and can be delivered to plants as a seed coat.

Sequencing and Analysis of the Entire Genome of the Mycoparasitic Fungus Trichoderma afroharzianum

Trichoderma sp. is a globally occurring fungal ascomycete. The genus Trichoderma belongs to the order of Hypocreales in the class of Sordariomycetes. Due to its importance as a mycoparasite and biocontrol fungus that antagonizes phytopathogenic and mycotoxin-producing fungi, the genome of the Trichoderma afroharzianum isolate BFE349 from the fungal strain collection of the Max Rubner-Institut was sequenced and analyzed.

Trichoderma sp. is a globally occurring fungal ascomycete. The genus Trichoderma belongs to the order of Hypocreales in the class of Sordariomycetes. Due to its importance as a mycoparasite and biocontrol fungus that antagonizes phytopathogenic and mycotoxin-producing fungi, the genome of the Trichoderma afroharzianum strain BFE349 from the fungal strain collection of the Max Rubner-Institut was sequenced and analyzed.

Effect of Colonization of Trichoderma harzianum on Growth Development and CBD Content of Hemp (Cannabis sativa L.)

Trichoderma harzianum, as a natural endophytic biocontrol agent, can ameliorate plant development, nutrient uptake, and resistance to biotic and abiotic stresses. This study aimed to investigate the effect of Trichoderma harzianum inoculation on agronomical and quality characteristics of two monoecious hemp (Cannabis sativa L.) varieties, Fedora 17 and Felina. A greenhouse pot experiment was conducted in a completely randomized design of two treatments of Trichoderma harzianum with a low and high dose of the fungus (T1 and T2). The significance of differences between treatments was estimated by using a Fisher’s test with a significance level p = 0.05. The root density of both varieties was significantly affected by treatments, and higher values were recorded in Fedora 17 (2.32 mm cm⁻³). The Arbuscular Mycorrhizal Fungi (AMF) colonization of the root system and the soil emission of CO₂ were higher after the inoculation of Trichoderma harzianum. The highest values of plant height and dry weight were noticed for T2, especially in variety Felina. Trichoderma harzianum positively influenced characteristics of inflorescences such as their number, fresh weight moisture, and compactness in both varieties, while the dry weight, length, and dry yield of inflorescences were not improved. Finally, the fertigation of Trichoderma harzianum in hemp plants was beneficial by increasing the cannabidiol (CBD) content, especially in T2 treatment (4 × 10¹² CFU kg⁻¹).