Chaetomium globosum is a potential biological control agent effective against various plant pathogens. Several reports are available on the mycoparastism and antibiosis mechanisms of C. globosum against plant pathogenic fungi, whereas a few states induced resistance. The potential induced defense component of C. globosum (Cg-2) was evaluated against early blight disease of tomato (Solanum lycopersicum) and further, global RNA sequencing was performed to gain deep insight into its mechanism. The expression of marker genes of hormone signaling pathways, such as PR1, PiII, PS, PAL, Le4, and GluB were analyzed using real-time quantitative reverse transcription PCR (qRT-PCR) to determine the best time point for RNA sequencing. The transcriptome data revealed that 22,473 differentially expressed genes (DEGs) were expressed in tomato at 12 h post Cg-2 inoculation as compared with control plants and among these 922 DEGs had a fold change of −2 to +2 with p < 0.05. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that most of the DEGs were belonging to metabolic pathways, biosynthesis of secondary metabolites, plant–pathogen interaction, chlorophyll metabolism, and plant hormone signal transduction. Gene Ontology (GO) analysis revealed that DEGs were enriched mainly related to binding activity (GO:0005488), catalytic activity (GO:0003824), metabolic process (GO:0008152), cellular process (GO:0009987), response to stimulus (GO:0050896), biological regulation (GO:0065007), and transcription regulator activity (GO:0140110). The gene modulations in hormone signaling transduction, phenylpropanoid biosynthesis, and mitogen-activated protein kinases (MPK) signaling indicated the upregulation of genes in these pathways. The results revealed active participation of jasmonic acid (JA) and salicylic acid (SA) signaling transduction pathways which further indicated the involvement of induced systemic resistance (ISR) and systemic acquired resistance (SAR) in the systemic resistance induced by Cg-2 in tomato.

Chaetomium globosum Kunze is recognized as a potential biocontrol fungus against spot blotch of wheat caused by Bipolaris sorokiniana. Its molecular mechanism of biocontrol activity and the biosynthetic pathways involved have not been yet elucidated. Here, global transcriptome profiling of C. globosum strain Cg2 during interaction with B. sorokiniana isolate BS112 using RNA-seq was performed in order to gain insights into the potential mechanisms of antagonism. The Illumina HiSeq platform (2 × 150 bp) yielded an average of 20–22 million reads with 50–58% GC. De novo assembly generated 45,582 transcripts with 27,957 unigenes. Transcriptome analysis displayed distinct expression profiles in the interaction (Cg2–BS112), out of which 6,109 unique differentially expressed genes were present. The predominant transcripts classified as genes involved in “catalytic activity” constituted 45.06%, of which 10.02% were associated with “hydrolytic activity” (GO:0008152), and similarly, in the biological process, 29.18% of transcripts were involved in “metabolic activity” (GO:0004096 and GO:0006979). Heat map and cluster categorization suggested an increase in the expression levels of genes encoding secondary metabolites like polyketide synthase (GO:0009058), S-hydroxymethyl glutathione dehydrogenase (GO:0006069), terpene cyclase (EC 4.2.3.-), aminotran_1_2 domain-containing protein (GO:0009058), and other hydrolytic CAZYmes such as the glycosyl hydrolase (GH) family (GH 13, GH 2, GH 31, and GH 81; GO:0005975), cellulase domain-containing protein, chitinases, β-1, 3-glucanases (GO:0004565), glucan endo-1,3-beta-glucanase (GO:0052861), and proteases (GO:0004177). The obtained RNA-seq data were validated by RT-qPCR using 20 randomly chosen genes, showing consistency with the RNA-seq results. The present work is worldwide the first effort to unravel the biocontrol mechanism of C. globosum against B. sorokiniana. It generated a novel dataset for further studies and facilitated improvement of the gene annotation models in the C. globosum draft genome.

Papaya (Carica papaya L.) is one of the important fruits cultivated in the tropical and subtropical regions are widely prone to the post-harvest anthracnose disease. A sum of ten isolates of Colletotrichum gloeosporioides were collected and identified through morphological and molecular method. Morphological characterization of the isolates revealed a wide variation among the isolates with respect to colony colour, topography, margin, pigmentation and zonation. The ITS gene region and the specific primer, MKCgF coupled with ITS-4, which generated amplicons of size 560 bp and 380 bp respectively for C. gloeosporioides. The amplicon (560 bp) of virulent strain Cg1 was partially sequenced [MF062699]. In order to formulate eco-friendly management practices, the in vitro screening of different biocontrol agents viz., Bacillus spp., Pseudomonas spp., plant extracts and essential oils were tested against the C. gloeosporioides. Based on the in vitro efficacy, Bacillus sp. (BSP1) and cinnamon oil were selected and further tested under field conditions as pre harvest spray and after harvest as fruit dipping. The experimental results revealed that pre-harvest spray with Bacillus sp. (BSP1) (5%) + post-harvest dipping with cinnamon oil (0.1%) recorded the lowest PDI of 3.25 when compared to control (70.36) and also increased the shelf life of papaya fruits up to 14 days. Our results show that this novel methodology of use a combination of biocontrol agent as pre-harvest spray and essential oils as post-harvest fruit dipping will protect against post-harvest anthracnose of papaya and use of chemical fungicides can be avoided.

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The fungus reported to be a potential antagonist of various soil and seed borne plant pathogens. C. globosum mycoparasitizes and produce antifungal metabolites which suppress the growth of the pathogenic fungi. Despite sufficient knowledge available on secondary metabolites of C. globosum and their wide biological activities, limited literatures are available on the polar active constituents and their potential use as antifungal agent. The study was carried out to evaluate chemical composition of secondary metabolites from C. globosum when it interacts with Bipolaris sorokiniana (2017-2020). The volatile compounds identified through GC-MS revealed that, C. globosum strain Cg2 produced a variety of antifungal secondary metabolites, i.e. octadecene trans-limonene oxide, dodecane, tetracosonal, heptacosanol and octadecanoic acid which may be involved in the antagonism. Similarly, UPLC-QToF-ESIMS analysis of chloroform soluble fraction of C. globosum (Cg2), B. sorokiniana (BS112) and their interaction (Cg2-BS112) were undertaken to identify non-volatile metabolites.These metabolites were identified as Chaetomugilin A, D, E, F, Globoxanthone A, Chaetoviridin A, B, E, Chaetoglobin B, Chaetoquadrin A, Chaetocochin B and F, Chaetoglobosin Q and N.The work indicates that the biocontrol agent C. globosum showed high antifungal metabolite production thereby antagonising B. sorokininana pathogen. The obtained data will greatly enrich current C. globosum metabolomic information and provide a good foundation for better understanding of biocontrol mechanism of C. globosum against plant pathogens and facilitating widespread application in the field of bio-control.

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Deciphering the network of interconnected pathways of Chaetomium globosum antagonistic related genes against Bipolaris sorokiniana using RNA seq approach ABSTRACT: Chaetomium species are known as potential biocontrol agents against phytopathogens due to their multiple antagonistic mechanisms. Plant disease is controlled by Chaetomium exhibit complex interactions against plant pathogen under varied conditions. Previously, mycoparasitism and antibiosis have been reported as most effective mechanism exhibited by the C. globosum against Bipolaris sorokiniana. In the present study, the examination of major biosynthetic pathways underlying Chaetomium globosum biocontrol activity was elucidated. It was shown that the pathways related to biosynthesis of secondary metabolites, hydrolytic enzymes and other key regulator genes were involved in production of hydrolytic enzymes and antifungal metabolites. We identified various genes of biological function with significant log2 fold change such as phosphoribosyl aminoimidazole carboxylase (9.693), protease (8.18), cyanate hydratase (Cyanase) (6.7), Fe2OG dioxygenase domain-containing protein (5.9), superoxide dismutase (5.55), glycosidase (5.34), carboxylic ester hydrolase (5.27), alpha-1,2-Mannosidase (4.44), alpha-1,4 glucan phosphorylase (3.99), endochitinase (3.87), P53-like transcription factor (Fragment) (3.55), metalloprotease (3.4), polyketide synthase (3.35), Catalase-peroxidase (CP) (3.14), protein kinase domain-containing protein (3.18) and glutamate decarboxylase (2.1) which are involved in biosynthesis of secondary metabolites, polyketide synthase, antibiotic, hydrolytic enzymes and putative fungistatic metabolites. This data provides a good foundation for continued researches into C. globosum Cg2 biocontrol activity for facilitating widespread application under the field conditions.

C. globosum is an endophytic fungus, which is recorded effective against several fungal and bacterial diseases in plants. The exclusively induce defense as mechanism of biocontrol for C. globosum against phyto-pathogens is reported. Our pervious study states the effectiveness of induced defense by C. globosum (Cg), in tomato against Alternaria solani. In this study the temporal transcriptome analysis of tomato plants after treatment with C. globosum was performed for time points at 0 hpCi, 12 hpCi, 24 hpCi and 96 phCi. The temporal expression analysis of genes belonging to defense signaling pathways indicates the maximum expression of genes at 12 h post Cg inoculation. The sequential progression in JA signaling pathway is marked by upregulation of downstream genes (Solyc10g011660, Solyc01g005440) of JA signaling at 24 hpCi and continued to express at same level upto 96 hpCi. However, the NPR1 (Solyc07g040690), the key regulator of SA signaling is activated at 12 h and repressed in later stages. The sequential expression of phenylpropanoid pathway genes (Solyc09g007920, Solyc12g011330, Solyc05g047530) marks the activation of pathway with course of time after Cg treatment that results in lignin formation. The plant defense signaling progresses in sequential manner with time course after Cg treatment. The results revealed the involvement of signaling pathways of ISR and SAR in systemic resistance induced by Cg in tomato, but with temporal variation.