Throughout history, plant diseases have posed significant challenges to agricultural progress, driven by both abiotic and biotic factors. Abiotic factors include wind, salt damage, freezing, girdling roots and compacted soil, while biotic factors encompass bacteria, nematodes, fungi and viruses. Plants have evolved diverse defense strategies to counter pathogen attacks, one of which involves chitinases, a subset of pathogenesis-related proteins. Chitinases are hydrolytic enzymes that degrade chitin, a high-molecular-weight linear polymer of N-acetylD-glucosamine, which is a crucial component of fungal cell walls and septa. These enzymes are produced by a wide range of organisms, including plants, animals, insects, fungi and microorganisms. In plants, chitinases are strongly expressed under pathogenic stress, primarily targeting fungal pathogens by breaking down their cell walls. They also contribute to cell wall remodeling and degradation during growth and defense processes. Numerous studies have demonstrated that the antifungal activity of chitinases is influenced by the chitin concentration and surface microstructure of different fungal species. Research has highlighted their role in protecting plants like mango, cucumber, rye, tomato, grapevine and other plants from various fungal diseases. These findings underscore the critical role of chitinases in plant defense mechanisms, showcasing their importance in mitigating fungal infections and supporting plant health.

Background Fungal infection predominantly damages agricultural practices, and conventional chemical fungicides and insecticides are applied to control it, which extensively harms human health and the environment. Some bacterial species can control fungus by lysing its outer chitin layer.Objectives The present research aimed to isolate microorganisms capable of producing chitinase, thus acting as a highly effective biocontrol agent in combating fungal phytopathogens.Methods Two chitinase-producing bacterial strains were successfully isolated and screened from soil samples from a fish market environment. The process involved the aseptic collection of soil samples, followed by serial dilution to facilitate microorganism isolation. The bacterium exhibited optimal extracellular chitinase enzyme production following a 72-h incubation period at a temperature of 30 degrees C in a chitinase detection medium containing 0.5% chitin. Validation of chitinase production was confirmed through a clear zone assay, thus verifying its chitinase-producing capacity.Results Among the various isolated strains, isolates S3C1 and S3C3 demonstrated the highest chitinase activity, leading to their selection for further investigation. Comprehensive morphological and biochemical tests were conducted on these two isolates to assess their characteristics and capabilities. These tests established that both isolates were gram-negative, rod-shaped bacteria. Through genetic sequencing of the 16S rRNA gene, both organisms were identified as Klebsiella variicola exhibiting a remarkable similarity of 99% with S3C1 and S3C3 respectively. The bacteria exhibited maximum chitinase synthesis at optimal circumstances, which were determined to be a temperature of 30 degrees C and a pH of 7, after a 48-h incubation period. The bacteria exhibited robust antifungal activity during bioassays, demonstrating their capability to suppress the growth of fungal pathogens (specifically, Fusarium oxysporum) in vitro.Conclusion This research suggests a promising alternative to synthetic fungicides in agricultural practices, fostering a sustainable approach to disease management.

Background Soil-borne plant diseases represent a severe problem that negatively impacts the production of food crops. Actinobacteria play a vital role in biocontrolling soil-borne fungi. Aim and objectives The target of the present study is to test the antagonistic activity of chitinase-producing Streptomyces cellulosae Actino 48 (accession number, MT573878) against Rhizoctonia solani. Subsequently, maximization of Actino 48 production using different fermentation processes in a stirred tank bioreactor. Finally, preparation of bio-friendly formulations prepared from the culture broth of Actino 48 using talc powder (TP) and bentonite in a natural as well as nano forms as carriers. Meanwhile, investigating their activities in reducing the damping-off and root rot diseases of peanut plants, infected by R. solani under greenhouse conditions. Results Actino 48 was found to be the most significant antagonistic isolate strain at p <= 0.05 and showed the highest inhibition percentage of fungal mycelium growth, which reached 97%. The results of scanning electron microscope (SEM) images analysis showed a large reduction in R. solani mycelia mass. Additionally, many aberrations changes and fungal hypha damages were found. Batch fermentation No. 2, which was performed using agitation speed of 200 rpm, achieved high chitinase activity of 0.1163 U mL- 1 min- 1 with a yield coefficient of 0.004 U mL- 1 min- 1 chitinase activity/g chitin. Nano-talc formulation of Actino 48 had more a significant effect compared to the other formulations in reducing percentages of damping-off and root rot diseases that equal to 19.05% and 4.76% with reduction percentages of 60% and 80%, respectively. The healthy survival percentage of peanut plants recorded 76.19%. Furthermore, the nano-talc formulation of Actino 48 was sufficient in increasing the dry weight of the peanut plants shoot, root systems, and the total number of peanut pods with increasing percentages of 47.62%, 55.62%, and 38.07%, respectively. Conclusion The bio-friendly formulations of actinobacteria resulting from this investigation may play an active role in managing soil-borne diseases.

As part of the development of alternative and environmentally friendly control against phytopathogenic fungi, Burkholderia cepacia could be a useful species notably via the generation of hydrolytic enzymes like chitinases, which can act as a biological control agent. Here, a Burkholderia contaminans S614 strain exhibiting chitinase activity was isolated from a soil in southern Tunisia. Then, response surface methodology (RSM) with a central composite design (CCD) was used to assess the impact of five factors (colloidal chitin, magnesium sulfate, dipotassium phosphate, yeast extract, and ammonium sulfate) on chitinase activity. B. contaminans strain 614 growing in the optimized medium showed up to a 3-fold higher chitinase activity. This enzyme was identified as beta-N-acetylhexosaminidase (90.1 kDa) based on its peptide sequences, which showed high similarity to those of Burkholderia lata strain 383. Furthermore, this chitinase significantly inhibited the growth of two phytopathogenic fungi: Botrytis cinerea M5 and Phoma medicaginis Ph8. Interestingly, a crude enzyme from strain S614 was effective in reducing P. medicaginis damage on detached leaves of Medicago truncatula. Overall, our data provide strong arguments for the agricultural and biotechnological potential of strain S614 in the context of developing biocontrol approaches.