Molecular Phylogeny of Endophytic Fungi from Rattan (Calamus castaneus Griff.) Spines and Their Antagonistic Activities against Plant Pathogenic Fungi

Palm Fungi and Their Key Role in Biodiversity Surveys: A Review

Over the past three decades, a wealth of studies has shown that palm trees (Arecaceae) are a diverse habitat with intense fungal colonisation, making them an important substratum to explore fungal diversity. Palm trees are perennial, monocotyledonous plants mainly restricted to the tropics that include economically important crops and highly valued ornamental plants worldwide. The extensive research conducted in Southeast Asia and Australasia indicates that palm fungi are undoubtedly a taxonomically diverse assemblage from which a remarkable number of new species is continuously being reported. Despite this wealth of data, no recent comprehensive review on palm fungi exists to date. In this regard, we present here a historical account and discussion of the research on the palm fungi to reflect on their importance as a diverse and understudied assemblage. The taxonomic structure of palm fungi is also outlined, along with comments on the need for further studies to place them within modern DNA sequence-based classifications. Palm trees can be considered model plants for studying fungal biodiversity and, therefore, the key role of palm fungi in biodiversity surveys is discussed. The close association and intrinsic relationship between palm hosts and palm fungi, coupled with a high fungal diversity, suggest that the diversity of palm fungi is still far from being fully understood. The figures suggested in the literature for the diversity of palm fungi have been revisited and updated here. As a result, it is estimated that there are about 76,000 species of palm fungi worldwide, of which more than 2500 are currently known. This review emphasises that research on palm fungi may provide answers to a number of current fungal biodiversity challenges.

Diaporthe Species on Palms: Molecular Re-Assessment and Species Boundaries Delimitation in the D. arecae Species Complex

Due to cryptic diversification, phenotypic plasticity and host associations, multilocus phylogenetic analyses have become the most important tool in accurately identifying and circumscribing species in the Diaporthe genus. However, the application of the genealogical concordance criterion has often been overlooked, ultimately leading to an exponential increase in novel Diaporthe spp. Due to the large number of species, many lineages remain poorly understood under the so-called species complexes. For this reason, a robust delimitation of the species boundaries in Diaporthe is still an ongoing challenge. Therefore, the present study aimed to resolve the species boundaries of the Diaporthe arecae species complex (DASC) by implementing an integrative taxonomic approach. The Genealogical Phylogenetic Species Recognition (GCPSR) principle revealed incongruences between the individual gene genealogies. Moreover, the Poisson Tree Processes' (PTPs) coalescent-based species delimitation models identified three well-delimited subclades represented by the species D. arecae, D. chiangmaiensis and D. smilacicola. These results evidence that all species previously described in the D. arecae subclade are conspecific, which is coherent with the morphological indistinctiveness observed and the absence of reproductive isolation and barriers to gene flow. Thus, 52 Diaporthe spp. are reduced to synonymy under D. arecae. Recent population expansion and the possibility of incomplete lineage sorting suggested that the D. arecae subclade may be considered as ongoing evolving lineages under active divergence and speciation. Hence, the genetic diversity and intraspecific variability of D. arecae in the context of current global climate change and the role of D. arecae as a pathogen on palm trees and other hosts are also discussed. This study illustrates that species in Diaporthe are highly overestimated, and highlights the relevance of applying an integrative taxonomic approach to accurately circumscribe the species boundaries in the genus Diaporthe.

Deposition of Daldinia starbaeckii (ELF) functionalized silver nanoparticles on urinary catheter tube using chitosan polymer to prevent microbial biofilms formation during UTI infection

Catheter-associated urinary tract infections (CAUTI) are the most common healthcare problem in hospitals. In this study, we isolated the Daldinia starbaeckii (An endolichenic fungus from Roccella montagnie) and its biomass extract were used to simultaneously synthesize and deposit DSFAgNPs on the inner and outer surfaces of the catheter tube using chitosan biopolymer via In-situ deposition method. Perfectly designed D. starbaeckii extract functionalized DSFAgNPs were characterized by UV spectroscopy, FTIR, SEM, EDS, TEM, and XRD. The microbial efficacy of DSFAgNPs & DSFAgNPs coated catheter (CTH3) was evaluated against eight human pathogenic gram (+ / -) ive strains and Candida albicans. Results indicated DSFAgNPs showed significant biological activity against both gram (+ / -) ive bacteria with an average MIC90 of 4 µl/ml. The most promising activity was observed against Helicobacter pylori. When bacteria strains allow to grow with CTH3 we reported significant reduction in colony formation unit (CFU/ml) in broth culture assay with an average 70% inhibition. Further, antibiofilm activity of CTH3 against P. aeruginosa showed strong inhibition of biofilm formation (85%). The study explored an alternate approach for significantly prevent CAUTI among hospital patients. We isolated an endolichenic fungus from lichen Roccella montagnei. The molecular characterization of fungus identified as Daldinia starbaeckii (DSF). The DSF was cultured and its fungal biomass exudes were used to simultaneously construct DSF-AgNPs and its deposition on the catheter surface using biopolymer chitosan via In-situ deposition method. Further, antimicrobial and antibiofilm efficacy of DSF-AgNPs was checked against urinary catheter contaminating and human pathogenic bacterial strains. Based on our research, we determined that DSF-AgNPs coating on a urinary catheter through this method is a cost-effective, eco-friendly approach to prevent catheter contamination.

Culturable endophytic fungal assemblages from Styrax sumatrana and Stryax benzoin and their potential as antifungal, antioxidant, and alpha-glucosidase inhibitory resources

Benzoin resin, produced by the native Indonesian trees Styrax sumatrana and Styrax benzoin, has been incorporated into medical practices to treat wounds, erythema, and many other conditions for centuries. Endophytic fungi that reside within medicinal plants have antimicrobial, antioxidant, and α-glucosidase inhibitory capacities, contributing to plant health and derivative products. In this study, we determined the antifungal, antioxidant, and α-glucosidase inhibitory capacities of endophytic fungal isolates from three different tissues (leaves, bark, and stems) of S. sumatrana and S. benzoin trees. The genera of fungal isolates were determined by phylogenetic analysis of internal transcribed spacer sequences. A total of 58 fungal isolates were classified into 15 different fungal genera from eight taxonomic orders—Hypocreales, Botryosphaeriales, Glomerellales, Diaphortales, Pleosporales, Eurotiales, Xylariales, and Mucorales—with a pattern of host species specificity. Among these isolates, Trichoderma sp. 6407 consistently exhibited high inhibition of the growth of plant pathogens Fusarium sp., Trichoderma viride, and Aspergillus niger. With respect to antioxidant activity, Phyllosticta sp. 6454 consistently showed 2,2-diphenyl-1-picrylhydrazyl inhibition (37.59 ± 0.05%), 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid)-based antioxidant activity (25.04 ± 0.27 mgTE/g), and α-glucosidase inhibitory activity (52.15 ± 10.08%). Neopestalotiopsis sp. 6431 was notably potent in 2,2-diphenyl-1-picrylhydrazyl inhibition (49.65 ± 0.80%), ferric reducing antioxidant power-based antioxidant activity (197.49 ± 8.65 mgTE/g), and α-glucosidase inhibitory activity (52.88 ± 4.93%). This study revealed that Trichoderma sp. 6407, Phyllosticta sp. 6454, and Neopestalotiopsis sp. 6431 exhibited antifungal, antioxidant, and α-glucosidase inhibitory activities.

Evaluation of the pathogenicity of endophytic fungi isolated from spines of rattan (Calamus castaneus) against other plant hosts

AIMS

In this study, we sought to determine the pathogenic ability of endophytic fungi recovered from the spines of Calamus castaneus, a common rattan palm growing in the forests of Peninsula Malaysia.

METHODS AND RESULTS

Ten endophytic fungal isolates were selected for pathogenicity tests: Colletotrichum boninense, C. fructicola, C. cliviae, Diaporthe hongkongensis, D. arengae, D. cf. nobilis, Neopestalotiopsis saprophytica, N. formicarum, Fusarium solani, and F. oxysporum. These endophytes were tested against leaves of bertam (Eugeissona sp.), oil palm (Elaeis guineensis), and mango (Mangiferae indica) and the fruits of chilli (Capsicum annum), tomato (Solanum lycopersicum), and banana (Musa acuminata). The fungal isolates showed infectivity against bertam, oil palm, and mango leaves with degrees of virulence ranging from low to moderate, whereas infectivity against chilli, tomato, and banana ranged from low to very high.

CONCLUSIONS

Fungal endophytes isolated from the spines of C. castaneus are pathogenic to different crop plants with differing degrees of virulence or aggressiveness.

SIGNIFICANCE AND IMPACT OF THE STUDY

Spines of C. castaneus can harbour fungal pathogens of a number of different crops as endophytes. The ability of the fungal endophytes to colonise and infect different crops demonstrate their importance towards agricultural crops. There is a possibility the endophytes behave as latent pathogen. When conditions become favourable, the fungal endophytes transform to pathogenic form and potentially infect other plants.

Fungal Endophytes and Their Role in Agricultural Plant Protection against Pests and Pathogens

Virtually all examined plant species harbour fungal endophytes which asymptomatically infect or colonize living plant tissues, including leaves, branches, stems and roots. Endophyte-host interactions are complex and span the mutualist-pathogen continuum. Notably, mutualist endophytes can confer increased fitness to their host plants compared with uncolonized plants, which has attracted interest in their potential application in integrated plant health management strategies. In this review, we report on the many benefits that fungal endophytes provide to agricultural plants against common non-insect pests such as fungi, bacteria, nematodes, viruses, and mites. We report endophytic modes of action against the aforementioned pests and describe why this broad group of fungi is vitally important to current and future agricultural practices. We also list an extensive number of plant-friendly endophytes and detail where they are most commonly found or applied in different studies. This review acts as a general resource for understanding endophytes as they relate to potential large-scale agricultural applications.