The bibliometric analysis was conducted using the Scopus database (Elsevier), selected for its comprehensive coverage of agricultural microbiology and biotechnology literature, as well as for its capacity to provide detailed metadata and compatibility with advanced network analysis and citation tools (Figure 1). The search was conducted on January 24, 2025, covering all publications indexed up to that date. To ensure an exhaustive retrieval of scientific papers, the following query was used in the Title, Abstract, and Keywords (TITLE-ABS-KEY) fields:

Trichoderma AND secondary metabolites AND biological control.

No restrictions were applied regarding language, document type, or subject category to ensure the inclusion of all relevant literature available in Scopus. The retrieved records were exported in CSV format, including metadata such as titles, abstracts, keywords, author affiliations, cited references, and citation metrics.

The data obtained were processed using the tools VOSviewer (v.1.6.19) (van Eck and Waltman, 2010) and Bibliometrix (Aria and Cuccurullo, 2017) selected for their efficiency in handling large volumes of data and their ability to generate complex network visualizations. In VOSviewer, keyword co-occurrence networks were generated, with a minimum frequency threshold established depending on the type of analysis, allowing for the identification of thematic clusters and emerging trends. Co-authorship and institutional collaboration networks were constructed using the association method available in VOSviewer, with the purpose of detecting relevant scientific communities in the field of study. In addition, productivity and impact metrics were calculated, including the H-index of authors and institutions, the geographical distribution of publications, and the temporal evolution of scientific production.

The results were synthesized into visual representations to facilitate the interpretation of research dynamics in the study area. Growth curves of the literature were generated using the R-Project software (version 4.4.3), applying a second-degree polynomial model to evaluate the increase in the number of studies and the emergence of new lines of research. Networks of co-occurring terms were analyzed to identify emerging patterns and predominant areas of research. Co-citation analysis was performed to identify the most influential articles and authors in research on Trichoderma secondary metabolites and their role in biocontrol. To evaluate the geographical contribution to scientific production, geospatial maps were constructed in Bibliometrix using affiliation data provided by Scopus, which allowed for the identification of the global distribution of publications and collaboration between countries, as described in Figure 1.

Indicators of the literature indexed in Scopus on Trichoderma and its secondary metabolites in the biological control of phytopathogens included 235 documents published in 151 sources (Figure 2). Scientific production grew at an annual rate of 5.7%, highlighting Trichoderma as a key tool in agricultural biotechnology, particularly in biological control and soil health improvement. Over the 25 years, research diversified into specialized areas such as soil microbiota modulation and omics technologies in agricultural protection. A total of 1,077 authors contributed to these papers, with an average of 5.54 co-authors per paper. However, only 29.36% of the publications included international co-authorship, indicating an opportunity to improve international collaboration, especially in regions with high agricultural potential such as Latin America, Africa, and Southeast Asia.

The documents analyzed included 15,305 references, with an average age of 6.15 years. The average number of citations per paper was 43.05, showing an uneven distribution of visibility among scientific articles; this pattern highlights the need to improve the scientific dissemination of key findings to increase the adoption of Trichoderma in agriculture. A total of 692 keywords were identified, reflecting the multidisciplinary nature of scientific production. Emerging areas, such as improved resistance to abiotic factors and interactions with beneficial microorganisms, remain underexplored and may represent new opportunities for future research to increase international collaboration and improve dissemination of findings to broaden the impact of Trichoderma in sustainable agriculture.

Scientific production has increased steadily since 2000, reaching a peak of 32 publications in 2023 (Figure 3). This growth follows a second-degree polynomial model (y = 9.04 + 3.9x + 10.9x²; R² = 0.62), which describes the acceleration of article production between 2010 and 2020, followed by a stabilization in recent years. Despite the continuous increase in the number of publications, the stabilization observed from 2020 onwards indicates a slowdown in the pace of scientific production in the most researched fields. The cumulative citations also show a similar evolution, reaching almost 3,000 citations in 2023, with fluctuations in 2024 and 2025 due to delays in indexing and the incomplete nature of the scientific production in 2025.

Of the 235 publications analyzed, 75% (180) were original articles, followed by systematic reviews (15%, n = 36), book chapters (6%, n = 16), and editorials (0.8%, n = 2) (Table 1). Systematic reviews stood out with an average of 3,245 citations, indicating a high impact within the thematic areas of research, while original articles accumulated 6,765 citations, with an h-index of 41. These data confirm the central role of original articles in generating knowledge in the Trichoderma field, with a more immediate impact in terms of citations. In contrast, book chapters and editorials had a significantly lower impact, with 93 and 2 citations, respectively. This low number of citations is related to the limitations of these types of scientific papers, which do not contribute significantly to the dissemination of experimental knowledge or to the formulation of new hypotheses.

The distribution of paper types reflects the predominance of original articles in the scientific production on Trichoderma. This trend is also consistent with the general pattern in experimental research areas. Although systematic reviews have an important impact on the organization and synthesis of information, their lower number of citations compared to original articles points to the difference in the speed of adoption of experimental results compared to more consolidating approaches. Finally, although the increase in scientific production and in the number of citations in the last decade indicates a greater interest in the subject, it is important to analyze and understand whether this growth is associated with an increased awareness of the benefits and challenges of biological control by Trichoderma and its contribution to agricultural sustainability.

The network analysis at the institutional level (Figure 4A) identified three main clusters, based on the density of connections and the size of the nodes. The cluster led by the Department of Agricultural Sciences at the University of Naples Federico II is characterized by a large central node with high scientific productivity in various research areas related to Trichoderma as a biological control agent. The second cluster, led by the Department of Veterinary Medicine and Animal Production at the Università degli Studi di Napoli Federico II, represents a medium-sized node, with dense connections associated with active collaboration in specialized areas within biocontrol and animal health. The third cluster, led by the Department of Pharmacy and Biology at the University of Salerno, features smaller nodes but with strong interactions, indicating a highly connected network in more specific research areas in biochemistry, genetics, and microbiology.

At the country level (Figure 4B), geographic analysis revealed three dominant clusters. India leads the first yellow cluster, with a large central node reflecting the largest amount of scientific output, and strong connections to countries such as Austria and Romania; this shows India’s growing involvement in Trichoderma research in Asia and its close connection to Europe. The purple cluster is led by Brazil, with medium-sized nodes and strong connections to the United States and Romania, highlighting collaboration in tropical agricultural systems. The third cluster, led by China, shows large nodes and extensive connections with Pakistan and Chile, highlighting its central role in scientific collaborations on a global scale.

Regarding the geographical distribution of scientific production (Figure 4C), India led with 50 publications, followed by China (38), Italy (24), and the United States (21). Brazil and Spain contributed 18 publications each, while Germany, Mexico, Austria, Iran, and Egypt recorded 12, 12, 11, 11, 11, 11, 11, and 10 publications, respectively. The lines connecting the countries in the figure represent the main international collaborative networks, with the strongest links between India and Austria, Brazil and the United States, and China and Pakistan. Finally, it is important to emphasize that the geographic distribution of publications and the connections between countries highlight the collective advancement of knowledge in Trichoderma research and its contribution to agricultural sustainability worldwide.

The keyword co-occurrence analysis (Figure 5A) shows four thematic groups related to the biocontrol effects of secondary metabolites of Trichoderma. The first group, highlighted in red, includes terms related to antifungal activity and biocontrol, such as biological pest control, antifungal activity, enzymatic activity, plant growth, and phytopathogens like Fusarium oxysporum and Rhizoctonia solani. These terms emphasize the focus on Trichoderma’s capabilities to inhibit pathogens and promote plant growth (Mousumi Das et al., 2019; Harman et al., 2004; Diánez et al., 2016). The second group, in green, includes terms related to genetic regulation and metabolic processes, such as genetics, metabolism, and microbiology, reflecting the interest in molecular mechanisms that enable Trichoderma to produce secondary metabolites with biocontrol potential (Hermosa et al., 2014; Wu et al., 2018; Fang et al., 2024). The third group, in blue, focuses on terms such as secondary metabolites, biocontrol, and Trichoderma, highlighting the importance of these compounds in suppressing phytopathogens and enhancing plant growth (Khan et al., 2020; Reino et al., 2008).

Finally, the yellow group includes terms such as biosynthesis and phylogeny, associated with research aimed at understanding the biosynthetic pathways and phylogenetic evolution of Trichoderma for the identification of strains with higher efficiency in secondary metabolite production (Gutiérrez et al., 2021; Guilger-Casagrande et al., 2019; Leiva et al., 2022). his cluster distribution presents how Trichoderma research is integrating molecular, metabolic, and ecological approaches to optimize its use in biocontrol and enhance plant protection, with clearly defined research lines.

The temporal evolution analysis (Figure 5B) revealed a transition in Trichoderma research over time. In the early periods (prior to 2016), studies focused predominantly on antifungal activity and biocontrol, emphasizing terms such as fungi and biological pest control. Between 2018 and 2020, there was an increase in the frequency of terms related to molecular and biochemical approaches, such as signal transduction, genetics, and plant growth. This temporal evolution demonstrates a progressive diversification of research lines, marking a shift from studies centered on the functional interactions of Trichoderma to those oriented toward the characterization of its metabolic and genetic mechanisms.

The thematic trend analysis (Figure 6A) organized research topics into three main plots. The first plot grouped terms related to antifungal activity and biocontrol, which showed high frequency in the initial years of the study period. The second plot focused on the production and regulation of secondary metabolites, with a notable increase in relevance from 2018 onwards. The third plot included terms associated with molecular biology and genetics, highlighting their growing importance in recent literature. This analysis confirms the transition from applied approaches to more fundamental research focused on the molecular and biochemical mechanisms that regulate Trichoderma’s biocontrol activity.

The conceptual structure map obtained by factor analysis (Figure 6B) organized key terms related to Trichoderma along two main dimensions. Dimension 1, explaining 47.16% of the variance, grouped concepts related to biocontrol and biotechnological applications of Trichoderma. Dimension 2, accounting for 27.78% of the variance, focused on molecular biology and biochemical processes. Terms such as signal transduction, biosynthesis, and gene expression, located in the upper right quadrant, reflect the increasing focus on the molecular mechanisms underlying Trichoderma’s biocontrol activity. The proximity of secondary metabolites and biocontrol agent indicates the relevance of secondary metabolites in biotechnological applications. Experimental terms such as high-performance liquid chromatography and enzyme activity highlight the use of advanced techniques to study and optimize the metabolic processes of Trichoderma in agricultural biocontrol.

The citation network (Figure 7A) is organized into clusters differentiated by color, where the size of the nodes indicates the volume of citations and the scientific influence of each country. India and China, with large nodes in the yellow and red clusters, lead scientific production, maintaining strong connections with Asian countries (Malaysia, Thailand, Indonesia) and European countries (Czech Republic, Poland). In the blue cluster, Italy and Poland, with medium-large nodes, show extensive transatlantic collaborations in agricultural and biotechnology research. The green cluster (Saudi Arabia, Germany) and the red cluster (China, Iran) contain smaller nodes, reflecting regional collaborations and emerging citation patterns. The purple cluster, which includes Egypt and Spain, represents collaborative links between Africa and Europe. This network configuration presents Asia and Europe as the primary regions for Trichoderma research, with collaborative links extending to Africa and Latin America.

Figure 7B shows the citation networks by author. Francesco Vinale has the highest number of citations and is positioned at the center of a large red cluster. Vinale collaborates with Matteo Lorito and Rosa E. Cardoza, forming a core group of shared references focused on the molecular and biochemical characterization of Trichoderma secondary metabolites and their application in biocontrol. The green cluster contains researchers such as Stefania Lanzuise and Nadia Lombardi, whose work on Trichoderma-phytopathogen interactions has generated substantial citations. The blue cluster, more compact and specialized, is led by Irina S. Druzhinina and Susanne Zeilinger, and focuses on genomics and metabolic regulation. The yellow cluster, more dispersed but with key links, includes Prasun K. Mukherjee and Charles M. Kenerley, whose contributions are referenced in a range of research areas, including molecular biology and agricultural applications.

Figure 7C presents the analysis of citations among journals, organized into four clusters representing areas of specialization and citation patterns in microbiology, phytopathology, and biological control. The green cluster, the largest and most interconnected, contains high-impact journals such as Applied and Environmental Microbiology and Nature Reviews Microbiology, representing studies on plant-microorganism interactions and applied biotechnology. The red cluster, more concentrated, includes journals such as Frontiers in Microbiology and Fungal Genetics and Biology, which focus on mycology and phytopathology. The blue cluster, more dispersed, connects journals in bioprospecting and microbial chemistry, such as the Journal of Natural Products and FEMS Microbiology Letters, which publish studies on the identification and characterization of secondary metabolites with biocontrol potential. The yellow cluster includes key journals such as Plant Disease and Biological Control, linking plant pathology with sustainable management practices.

Figure 7D shows the distribution of total and average citations by country. Italy leads with 1,751 total citations and an average of 103 citations per publication, followed by India (1,137 total citations) and the United States (1,030 total citations), both with an average of 103 citations per publication. Canada records 876 total citations, with an average of 175.2 citations per publication. China, with 942 total citations, has a lower average of 27.7 citations per publication. Spain has 789 total citations, with an average of 131.5 citations per publication. Countries such as Israel (329 total citations), Malaysia (421), Austria (488), and Mexico (413) have lower total citation counts, with averages ranging from 68.8 to 140.3 citations per publication. This distribution shows variation in the visibility and citation impact of research, with Canada and Malaysia having high impact per article, and China and India having higher publication volumes but lower citation averages.

The analysis of the most cited papers on Trichoderma (Table 2) shows that the study by Vinale et al. (2008) has 925 citations, followed by Verma et al. (2007) with 523 citations. The distribution includes original research articles (n = 5) and systematic reviews (n = 5). Experimental studies by Yedidia et al. (2003) and Howell et al. (2000) report data on the induction of systemic resistance in plants and the production of bioactive metabolites with antifungal activity. Reviews by Reino et al. (2008) and Mukherjee et al. (2013) compile information on the characterization of secondary metabolites and the genomic analysis of Trichoderma.

Publications are concentrated in high-impact journals such as Soil Biology and Biochemistry, Annual Review of Phytopathology, and Applied and Environmental Microbiology. The temporal range of publications spans from 2000 to 2024, with an increase in citations in recent years. Recent studies, including those by Zin and Badaluddin (2020) on the biological functions of Trichoderma in agriculture, and Poveda et al. (2020) on its role in the biological control of plant-parasitic nematodes through the induction of resistance, contribute to the body of knowledge on Trichoderma’s use in improving plant health and agricultural productivity.

Scientific production on Trichoderma secondary metabolites in biocontrol has experienced a continuous growth since 2006, with a significant concentration of publications in recent years (Figure 8A). Francesco Vinale leads the scientific production with 14 publications, followed by Matteo Lorito and Roberta Marra, each with 8 publications. Other authors, such as Sheridan L. Woo, Prasun K. Mukherjee and Santiago Gutierrez, have increased their production in recent years, showing a trend of research on gene regulation and biosynthesis of secondary metabolites. Although Susanne Zeilinger and Dan F. Jensen have a smaller number of publications, their contributions have been fundamental in the study of the interaction between Trichoderma and the soil microbiota.

In the co-authorship network (Figure 8B), five main clusters are identified, each characterized by different connection densities. The yellow cluster, with the highest density, groups Francesco Vinale, Bubici Giovanni, and Starapoli Alessia, forming a central collaboration network focused on biological control and interactions with beneficial microorganisms in agriculture (Vinale et al., 2008; Prigigallo et al., 2023). The blue cluster, which includes Vitaglione Paola and Sheridan L. Woo, maintains a high connection density within the cluster but shows limited collaboration with other groups. This cluster is associated with research on plant biostimulation, performance parameters, and the eco-physiological processes of Trichoderma in sustainable agriculture (Woo et al., 2023; Woo et al., 2014).

The green cluster, composed of Roberta Marra and Matteo Lorito, focuses on research related to the functionality of bioactive metabolites in plant physiology (Marra et al., 2019); as well as the characterization of the transcriptome and metabolome of Trichoderma in its biotic interactions within the ecosystem (Lorito et al., 2010). The red cluster, which includes researchers such as Santiago Gutiérrez and Rosa Hermosa, concentrates on the study of Trichoderma genes involved in plant interactions, particularly those that promote growth and enhance resistance to both biotic and abiotic stress. These studies have analyzed the expression of genes such as ThPG1 and hsp70, which contribute to improving plant defense capacity against pathogens and adverse conditions, including heat and osmotic stress. Research by Morán-Diez et al. (2009), Montero-Barrientos et al. (2010), and Hermosa et al. (2012) has reported that the manipulation of these genes in plants can increase resistance levels, contributing to the development of crops with improved tolerance to diseases and extreme environmental conditions.

The purple cluster, which includes Sarma Kumar and other authors, contains smaller yet complementary contributions. The majority of influential authors are affiliated with institutions in Italy and Spain. In recent years, there has been an increase in scientific output from researchers in India, with contributions to the field of biological control (Manzar et al., 2022; Manzar et al., 2024; Kashyap and Manzar, 2025; Manzar et al., 2021).

Citation indicators (Table 3) indicate that Francesco Vinale, Matteo Lorito, and Roberta Marra hold the highest citation counts, with 1,755, 1,533, and 1,408 citations, respectively. Although Sheridan L. Woo and Prasun K. Mukherjee have fewer publications, their citation-to-publication ratio is comparatively high. For example, Woo has 1,246 citations across 6 publications, and Mukherjee has 537 citations from 5 publications. These data provide an overview of author productivity and the citation impact of their contributions within the field.

The bibliometric network of journal co-citation (Figure 9) presents a structure in which Frontiers in Microbiology is the most central node, showing strong interconnections with journals focused on microbiology and biotechnology, including BMC Genomics and Applied Microbiology and Biotechnology. Thematic clusters are identified: the blue cluster includes journals dedicated to general microbiology and genomics; the red cluster is oriented towards applied biotechnology and soil biochemistry; the green cluster focuses on soil chemistry, biodiversity, and environmental contaminants; and the orange cluster relates to biological control and phytopathology. The connections among these clusters reflect an interdisciplinary structure in biocontrol research, with biotechnology and microbiology linked to the understanding and application of Trichoderma-based strategies.

The bibliometric metrics of the ranking of journals with the highest scientific production (Table 4) indicate that Frontiers in Microbiology has the highest number of documents (21), h-index (14), and total citations (1,030). Biological Control and Journal of Fungi have an h-index of 4 and total citations of 85 and 92, respectively. The m-index analysis shows that Frontiers in Microbiology has a citation rate of 1.4. Journals such as 3 Biotech and Phytopathology have a lower publication volume but a relatively high number of accumulated citations, reflecting their specific contribution to the development of biocontrol strategies. Scientific production in the field of Trichoderma-based biological control is concentrated in medium-to high-impact journals, including applied studies and fundamental research in microbiology and phytopathology.

Figure 10 presents the temporal dynamics of key research terms in the study topic. Since 2000, terms such as metabolites, plant pathogens, and antagonism have increased in frequency, corresponding to an initial focus on direct biocontrol mechanisms, including the production of antifungal compounds and ecological competence (Vinale et al., 2008; Verma et al., 2007). From 2016 onwards, there is an increase in the frequency of terms such as antifungal activity, induced systemic resistance (ISR), and bioactive peptides, associated with a transition toward molecular studies and plant–microorganism interactions (Shoresh et al., 2010; Poveda et al., 2020).

Species such as T. harzianum and T. viride maintain a consistent presence in the literature and the biofungicide market, linked to their efficacy in controlling pathogens such as Fusarium oxysporum and Rhizoctonia solani (Mousumi Das et al., 2019; Manzar et al., 2021). This trend corresponds with the increasing demand for sustainable alternatives to the excessive use of agrochemicals, which has led to efforts to reduce microbial resistance and the environmental impact associated with synthetic pesticide residues (María Suaste, 2020; Ribeiro et al., 2001).

The comprehensive analysis of the 235 scientific publications on Trichoderma as a biocontrol agent indicates a complex interaction of biological, environmental, and technological factors. Data indicate that T. asperellum achieves an efficacy of 92.2% against Colletotrichum gloeosporioides in tomato crops, primarily through the production of antifungal metabolites (peptaibols, 2-aminoisobutyric acid) and rapid colonization of the rhizosphere (Alfaro-Vargas et al., 2022). In contrast, efficacy is reduced to 53% against oomycetes such as Phytophthora infestans on potato, due to differences in cell wall composition (Alfiky et al., 2024). Biocontrol efficacy varies between controlled and field conditions: in vitro studies report control levels of 80–100%, whereas field studies show lower efficacy, typically ranging from 40–60%. Reductions in efficacy are more pronounced in clay soils (35% lower than in loam soils) and under elevated temperatures (>30°C) (Shao et al., 2025; Zin and Badaluddin, 2020).

The variation in biocontrol efficacy is influenced by environmental factors such as soil pH, soil texture, and the presence of competing microorganisms variables that are rarely considered in current experimental designs (Poveda et al., 2020). Additionally, methodological limitations are identified: only 18% of the studies evaluate commercial formulations or optimized application strategies, and few investigate advanced methods such as nanoencapsulation of metabolites (Shao et al., 2025). These aspects contribute to the gap between laboratory results and practical applications in agricultural systems.