At the seedling and adult plant phases, pot experiments were carried out to enhance the physiological-biochemical characteristics of cucumber, guarantee its high yield, and ensure its cultivation of quality. Trichoderma harzianum conidia agents at 10⁴, 10⁵, 10⁶, and 10⁷ cfu g⁻¹ were applied in accordance with the application of Fusarium oxysporum powder at concentrations of 10⁴ cfu/g on the protective enzyme activity, physiological and biochemical indices, seedling quality, resilience to Fusarium wilt, quality, and yield traits. Fusarium oxysporum powder at 10⁴ cfu g⁻¹ was used to treat CK1, while Fusarium oxysporum powder and T. harzianum conidia agents were not used to treat CK2. The results show that different T. harzianum agents improved the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), and peroxidase (POD) in cucumber seedlings, improved chlorophyll content, root activity, root-shoot ratio, and seedling strength index, and decreased malondialdehyde (MAD) content (P < 0.05). T3, a combination of 10⁴ cfu g⁻¹ Fusarium oxysporum powder and 10⁶ cfu g⁻¹ T. harzianum conidia agents, had the greatest promoting effect. The effects of different T. harzianum conidia agents and their application amounts on the control of cucumber Fusarium wilt were explored. T3 had the best promotion impact, and the control effect of cucumber Fusarium wilt at seedling stage and adult stage reached 83.98% and 70.08%, respectively. The quality index and yield formation of cucumber were also increased by several T. harzianum agents, with T3 having the strongest promotion effects. In comparison to CK1, the soluble sugar, Vc, soluble protein, and soluble solid contents of T3 cucumber fruit were 120.75%, 39.14%, 42.26%, and 11.64% higher (P < 0.05), respectively. In comparison to CK2, the soluble sugar, Vc, soluble protein, and soluble solid contents of T3 cucumber fruit were 66.06%, 24.28%, 36.15%, and 7.95% higher (P < 0.05), respectively. In comparison to CK1 and CK2, the yields of T3 cucumber were 50.19% and 35.86% higher, respectively. As a result, T. harzianum agents can enhance the physiological and biochemical traits of cucumber seedlings, raise the quality of cucumber seedlings, have a controlling impact on Fusarium wilt, and increase the yield and quality of cucumber fruit. The greatest effectiveness of T3 comes from its use. In this study, Trichoderma harzianum conidia agents demonstrated good impacts on cucumber yield formation and plant disease prevention, demonstrating their high potential as biocontrol agents.

Background: Trichoderma spp. are used extensively in agriculture as biological control agents to prevent soil-borne plant diseases. In recent years, mycoviruses from fungi have attracted increasing attention due to their effects on their hosts, but Trichoderma mycoviruses have not been the subject of extensive study. We sought to discover novel mycoviruses from Trichoderma spp. and to determine the effects of the biocontrol function of Trichoderma spp. Methods: Mycoviruses were screened by dsRNA extraction and metagenomic analysis. RT-PCR, 5′ RACE, and 3′ RACE were used to obtain the genome sequence. MEGA software was used to classify the new mycovirus. The effects of the identified mycovirus on the biological properties of the host strain 525 were evaluated using cucumber plants and Fusarium oxysporum f. sp. cucumerinum. Results: A novel mycovirus, Trichoderma harzianum mycovirus 1 (ThMV1) (accession number MH155602), was discovered in Trichoderma harzianum strain 525, a soil-borne fungus collected from Inner Mongolia, China. The mycovirus exhibited a double-stranded RNA (dsRNA) genome with a complete genome sequence of 3160 base pairs and two open reading frames (ORFs) on the negative strand. Phylogenetic analysis indicated that it belongs to an unclassified family of dsRNA mycoviruses. The removal of ThMV1 from the host 525 strain reduced host biomass production and improved the biocontrol capability of the host for Fusarium oxysporum f. sp. cucumerinum. At same time, the presence of ThMV1 improved the growth of cucumber. Conclusion: ThMV1 is a new unclassified mycovirus found in T. harzianum. It not only affects the phenotype of the host strain but also reduces its biocontrol function, which sheds light on the interaction between the mycovirus and Trichoderma spp.

Identification of loci or genes under natural selection is important for both understanding the genetic basis of local adaptation and practical applications, and genome scans provide a powerful means for such identification purposes. In this study, genome-wide simple sequence repeats markers (SSRs) were used to scan for molecular footprints of divergent selection in Eucalyptus grandis, a hardwood species occurring widely in costal areas from 32° S to 16° S in Australia. High population diversity levels and weak population structure were detected with putatively neutral genomic SSRs. Using three F_ST outlier detection methods, a total of 58 outlying SSRs were collectively identified as loci under divergent selection against three non-correlated climatic variables, namely, mean annual temperature, isothermality and annual precipitation. Using a spatial analysis method, nine significant associations were revealed between F_ST outlier allele frequencies and climatic variables, involving seven alleles from five SSR loci. Of the five significant SSRs, two (EUCeSSR1044 and Embra394) contained alleles of putative genes with known functional importance for response to climatic factors. Our study presents critical information on the population diversity and structure of the important woody species E. grandis and provides insight into the adaptive responses of perennial trees to climatic variations.

Heterotrimeric G-proteins are key elements of signal transduction pathways, which participate in regulating multiple biological processes in fungi including growth, conidiation, antagonism, and mycoparasitism. Among G protein subunits, Gα3 showed diverse regulatory functions in different fungi. In this study, we cloned a Gα3 subunit coding gene thga3 from T. harzianum Th33 that can antagonize Rhizoctonia solani and some other plant pathogenic fungi. A thga3 deletion strain Δthga3 was generated using the double-crossover homologous recombination strategy, and Rthga3 was generated by transforming thga3-expressing vector into the protoplasts of Δthga3 by the PEG/CaCl₂-mediated method. The biological characteristics of wild-type Th33, Δthga3 and Rthga3 were evaluated. Compared with wild-type Th33, Δthga3 showed 15%, 94%, and 23% decrease in hyphal growth, conidia yield, and chitinase activity, respectively, and Δthga3 showed lower antagonistic and mycoparasitism abilities, while there were no significant differences between wild-type Th33 and Rthga3. The hyphal surface hydrophobicity of Δthga3 significantly decreased compared with those of the wild-type Th33 and Rthga3. qRT-PCR analysis revealed that transcript abundance of the hydrophobin gene (tha_09745) of Δthga3 decreased by 80% compared with that of wild-type Th33 and Rthga3. The results showed that thga3 positively regulates the growth, conidiation, hydrophobicity, chitinase activities, and mycoparasitism of Th33 towards R. solani. We hence deduced that the expression level of Tha_09745 is correlated to the hyphal hydrophobicity of Th33 and therefore affects the other biological characteristics of Th33. The findings of this report provide a foundation for elucidating the G-protein signal regulatory mechanisms of fungi.

Two types of Trichoderma longibrachiatum Tr58 propagules, conidia and chlamydospores, were added to soils with different moisture levels. The survival dynamics of Tr58 in soils were determined. There are positive linear relationships between soil moisture levels and germination rates of the two propagules. In natural non-sterilized soil, the germination of more than 95% conidia and 60% chlamydospores was inhibited, while a high soil moisture content and sterilization were beneficial to spore germination. The inhibitory effect of soil with 80% moisture content on the germination of chlamydospores was almost completely eliminated after sterilization. Twelve months after the conidia inoculated to the natural soil, the Tr58 propagules decreased continuously, which was hastened in soils with lower moisture content and almost near zero 24 months later, in all soils. In chlamydospore-amended soils, the Tr58 propagules generally showed a dynamic process of decreasing in the first month, increasing in the 2nd month, and then decreasing gradually. The average Tr58 content in chlamydospore-amended soils with 5, 10, 20, 40, and 80% moisture content was 19.2 times that of conidia-amended soils at 12 months. At 24 months, the Tr58 content was about 2.2% of the initial Tr58 content and 114 times that of conidia in soils with 20% moisture content. However, for 80% moisture content, the Tr58 content in soil was 0.0038% of the initial content of Tr58. According to the results of this study, 10–20% soil moisture content was the most favorable for the long-term survival of Tr58, and the survival ability of chlamydospores was stronger than that of conidia and had greater application potential in disease control.

Trichodermaspp. are important biocontrol filamentous fungi and have tremendous potential in soil bioremediation. In our previous studies, a C2H2 type transcription factor coding gene (thmea1) was cloned from a biocontrol agentT. harzianumTh-33; the encoded sequence ofthmea1contained 3 conserved C2H2 domains with Swi5 and Ace2 inSaccharomyces cerevisiae. Thethmea1knockout mutantΔthmea1showed 12.9% higher copper tolerance than the wild-type Th33. To elucidate the function ofthmea1and its relationship with copper stress response, we conducted transcriptome sequencing and analysis of wild-type Th33 andΔthmea1under 0.8 mM copper stress. A total of 1061 differentially expressed genes (DEGs) were identified between the two strains, all DEGs were assigned to KEGG pathway database, 383 DEGs were annotated in 191 individual pathways, and the categories of ribosomal protein synthesis and amino acid metabolism were the most highly enriched ones. Analysis of related DEGs showed that the expression levels of intracellular glutathione detoxification enzyme, heat shock proteins, and ribosomal proteins inΔthmea1were higher than that of the wild-type Th33, and the expression of metallothionein (MT) gene did not change. In addition, the expression levels of genes coding for proteins associated with the Ccc2p-mediated copper chaperone Atx1p transport of copper ions into the Golgi secretory pathway increased, as well as the copper amine oxidase (CuAO). These findings suggest that Thmea1 is a negative regulated factor of copper tolerance ability inT. harzianum. It does not show metallothionein expression activator activities as that of Ace2 inS. cerevisiae. We hypothesize that afterT. harzianumhas lost itsthmea1gene, the ability of cells to scavenge reactive oxygen species, mainly through the glutathione antioxidant system, is enhanced, whereas protein synthesis and repair and copper secretion increase under copper stress, which increases the ability of the mutant strain to tolerate copper stress.