Mei Li

Chlamydospores are thick-walled, dormant propagules formed by fungi in response to environmental stress. They play contrasting roles in plant protection: serving as persistent inocula of soil-borne pathogenic fungi that contribute to recurrent disease outbreaks, while also acting as highly stress-resistant propagules for fungal biocontrol formulations. This review examines the ultrastructure, regulation of differentiation, soil survival, and germination behaviour of fungal chlamydospores. It compares diverse survival strategies among pathogenic fungi and discusses natural disease-suppressive mechanisms, including soil fungistasis and germination–lysis. Furthermore, this review highlights the field application advantages of chlamydospores from Trichoderma and nematophagous biocontrol fungi, together with functionally analogous microsclerotia from entomopathogenic fungi. Finally, we identify major challenges in understanding the molecular regulation of chlamydospores, standardizing formulations, and quantitatively characterizing their ecological dynamics in soil. Addressing these challenges will support the sustainable management of soil-borne diseases and the development of fungal biocontrol products.

The issue of ongoing cropping barriers is getting worse as China’s melon planting area steadily grows, and the melon industry’s sustainable growth is being negatively impacted by the steadily diminishing yield and quality of the fruit. Trichoderma is a probiotic that can enhance the physiological traits of crops, encourage their growth, and raise their yield and quality. It is yet unknown, though, how Trichoderma influences the growth, physiological traits, and yield of melon grown on soils continuously cropped to melon. Trichoderma viride kf57 agents at 1.0 × 10⁴, 8.0 × 10⁴, 6.4 × 10⁵, and 5.12 × 10⁶ CFU/g and no Trichoderma viride agents (CK) were utilized as treatments. At the seedling and fruiting stages, a pot experiment and a bedding experiment were conducted to study the physiological properties and yield of melon under varying concentration of Trichoderma viride kf57 agents. As a result of the application of T. viride agents, the indexes of melon seedlings were all significantly improved. The treatment of 6.4 × 10⁵ CFU/g had the best promoting effect on the morphology of melon seedlings, and the plant height, stem diameter, leaf area, fresh weight of whole plant, dry weight of whole plant, root shoot ratio, and strong seedling index of melon seedlings increased by 90.39, 46.30, 37.55, 81.35, 100.62, 51.47, and 240.00%, respectively, compared with CK. The results showed that different amounts of T. viride agents could improve physiological and biochemical indices of melon leaves during the fruiting stage; the treatment of 6.4 × 10⁵ CFU/g was the most effective; chlorophyll content, nitrate nitrogen content, sucrose content, reducing sugar content, free proline content, nitrate reductase (NR) activity, peroxidase (POD) activity, and superoxide dismutase (SOD) activity of melon leaves increased at 30 days after melon pollination. Melon quality and yield was also enhanced by the use of T. viride agents, with the treatment of 6.4 × 10⁵ CFU/g T. viride agents having the best boosting effects. The melon fruit’s transverse diameter, vertical diameter, single fruit weight, and yield all increased. The amount of soluble solids, vitamin C, soluble protein, soluble sugar, and sugar acid ratio also increased. In conclusion, by promoting the morphology of melon grown on soils continuously cropped to melon seedlings, T. viride agents can improve the physiological characteristics of melon grown on soils continuously cropped to melon and improve the production and quality qualities of melon. When using T. viride kf57 agents, 6.4 × 10⁵ CFU/g is the highest effective dosage. The study revealed that T. viride agents had significant potential as biological agents as they showed good results in melon yield and quality formation, as well as in enhancing seedling quality.

Melon damping off, which has a negative impact on melon quality and yield, can be safely and effectively managed with Trichoderma. Melon cultivar ‘Longtian No. 1’ was evaluated at both the adult and seedling stages in a pot experiment. The Rs and PD liquids were utilized as CK1 and CK2, respectively. Trichoderma viride Tv286 treatments T1B, T2B, T3B, and T4B were used based on Rs at concentrations of 10⁴, 10⁵, 10⁶, and 10⁷ CFU·g⁻¹, respectively. The impact of several treatments on the antioxidant system and seedling quality of melon were assessed at 15, 25, and 35 days after sowing. We examined the effects of several treatments on melon quality, yield attributes, and physiological and biochemical markers during the adult stage at 10, 20, and 30 days after pollination. The effects of several treatments on melon damping off were also studied. Applying T. viride Tv286 at different rates effectively increased the activities of enzymes, including catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), ascorbate peroxidase (APX), and polyphenol oxidase (PPO), in the leaves of melon seedlings, significantly reduced the malondialdehyde (MDA) content, and improved the root–shoot ratio and seedling strength index. In terms of its influence on promoting the effect of antioxidant system indicators, T3B performed well. Melon seedlings treated with T3B showed higher CAT, POD, SOD, APX, and PPO activities in their leaves 35 days after sowing compared to CK1 (189.74, 169.61, 175.36, 224.20, and 477.39%, respectively). The strong seedling index and root–shoot ratio showed improvements of 130.43 and 79.71%, respectively, and the MDA content dropped by 35.66% at 35 days after sowing compared to CK1. Varying the rates at which T. viride Tv286 was applied increased the nitrate reductase (NR) activity and nitrate nitrogen, proline (Pro), chlorophyll, soluble sugar, and soluble protein contents in mature melon leaves, increasing melon quality and yield. T3B is the most effective marketing campaign. Compared to CK1, mature T3B leaves had higher NR activity, nitrate nitrogen content, chlorophyll content, soluble sugar content, soluble protein content, and Pro content 30 days after melon pollination (100.40, 135.17, 68.59, 93.65, 158.13, and 238.67%, respectively). The soluble solids, soluble protein, soluble sugar, vitamin C contents, and yield of melon fruit increased by 50.07, 126.82, 60.62, 70.79, and 61.45%, respectively, at 30 days after melon pollination compared to CK1. Optimal management of melon damping off can be accomplished with the application of T. viride Tv286 at different concentrations, with T3B exhibiting the best effect. The control effects reached 90.48 and 72.99% at the seedling and adult stages, respectively. Overall, T. viride Tv286 improved seedling quality, damping off control efficacy, melon yield and quality, and the antioxidant system during the seedling stage and enhanced physiological and biochemical characteristics during the adult stage. This study indicates the potential of T. viride Tv286 conidia as a biological control agent because it can prevent plant disease, increase yield, and improve quality.

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.

Trichoderma spp. are widely used in plant disease control as biocontrol agents. Inducing plant disease resistance is an important biocontrol mechanism of Trichoderma. It is of great significance to explore the factors involved in the surface recognition and interaction of Trichoderma with plants. Hydrophobin is a small molecular protein rich in cysteine in higher filamentous fungi and has been found to participate in the morphogenesis and interaction of fungi with other organisms. In this study, the type II hydrophobic protein-coding gene Thfb6 from T. harzianum TH33 was cloned and heterologously expressed in Escherichia coli BL21 (DE3). The purified recombinant protein Thfb6 induced a hypersensitive response in tobacco leaves, a burst of reactive oxygen species, and an accumulation of callose, phenolic substances, and lignin in tobacco, indicating that Thfb6 can induce an early defense reaction in tobacco. Thfb6 also enhanced the systemic resistance of tobacco against tobacco mosaic virus. The rate of lesion number reduction by treatment with Thfb6 could be up to 36.02%. Thfb6 increased the activity of tobacco defense-related enzymes, including phenylalanine ammonia-lyase (PAL), polyphenol oxidase, and peroxidase, which were all more than three times the control after 3–5 days post treatment of Thfb6. The transcription of resistance-related genes, including the PAL gene, non-expresser of pathogenesis-related gene1 (NPR1), and basic pathogenesis-related gene 1 (PR1-b), were upregulated after Thfb6 treatment. The relative expression levels of the PAL and NPR1 genes were highest on the third and fourth days after Thfb6 treatment, at 5.5 times and 8.3 times that of the control, respectively. The relative expression level of PR1 on the sixth day after Thfb6 treatment was 5.3 times that of the control. These results indicate that the improvement of defense-related enzyme activity and the induced expression of disease-resistance-related genes were the main mechanisms by which Thfb6 induced systemic resistance in tobacco.

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.

Background The medicinal woody leguminous genus Archidendron F. Mueller serves as important herbal resources for curing upper respiratory tract infection, acute pharyngitis, tonsillitis, and gastroenteritis. However, genomic resources including transcriptomic sequences and molecular markers remain scarce in the genus. Methods and results Transcriptome sequencing, genic microsatellite marker development, and population diversity analysis were conducted in Archidendron clypearia (Jack) I.C. Nielsen. Flower and flower bud transcriptomes were de novo assembled into 173,172 transcripts, with an average transcript length of 1597.3 bp and an N50 length of 2427 bp. A total of 34,701 microsatellite loci were identified from 26,716 (15.4 %) transcripts. Primer pairs were designed for 718 microsatellite loci, of which 456 (63.5 %) were polymorphic. Of the 456 polymorphic markers, 391 (85.7 %) and 402 (88.1 %) were transferable to A. lucidum (Benth.) I.C. Nielsen and A. multifoliolatum (H.Q. Wen) T.L. Wu, respectively. Using a subset of 15 microsatellite markers, relatively high genetic diversity was detected over two A. clypearia populations, with overall mean expected heterozygosity (H_e) being 0.707 and demonstrating the necessity of conservation. Relatively low differentiation between the two populations was revealed despite the distant separation (about 700 km), with overall inbreeding coefficient of sub-population to the total population (F_st) being 8.7 %. Conclusions This study represents the first attempt to conduct transcriptome sequencing, SSR marker development, and population genetics analysis in the medicinally important genus Archidendron. Our results will offer valuable resources and information for further genetic studies and practical applications in Archidendron and the related taxa.

Development of SSR Markers Associated with Polima CMS Fertility Restorer in Brassica napus L. and Its Application

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.

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 Δ thga3 was generated using the double-crossover homologous recombination strategy, and R thga3 was generated by transforming thga3 -expressing vector into the protoplasts of Δ thga3 by the PEG/CaCl 2 -mediated method. The biological characteristics of wild-type Th33, Δ thga3 and R thga3 were evaluated. Compared with wild-type Th33, Δ thga3 showed 15%, 94%, and 23% decrease in hyphal growth, conidia yield, and chitinase activity, respectively, and Δ thga3 showed lower antagonistic and mycoparasitism abilities, while there were no significant differences between wild-type Th33 and R thga3 . The hyphal surface hydrophobicity of Δ thga3 significantly decreased compared with those of the wild-type Th33 and R thga3 . qRT-PCR analysis revealed that transcript abundance of the hydrophobin gene (tha_09745) of Δ thga3 decreased by 80% compared with that of wild-type Th33 and R thga3 . 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.