Exploring low-dose gamma radiation effects on monoterpene biosynthesis in Thymus vulgaris: insights into plant defense mechanisms.

Thymus vulgaris, commonly known as thyme, is a plant renowned for producing monoterpenes. This study aimed to understand the effects of low-dose gamma radiation, specifically in the range of 1-5 Gy, on various traits of Thymus vulgaris, providing context on its importance in agricultural and medicinal applications. The research explored morpho-physiological, biochemical, and gene-expression responses in thyme plants under no gamma- and gamma-ray exposure conditions. The study revealed complex relationships between gamma-ray doses and plant characteristics. In particular, shoot and root lengths initially increased with low doses (1-3 Gy) but decreased at higher doses (5 Gy), suggesting a dose-dependent threshold effect. Similarly, shoot and root fresh weights displayed an initial increase followed by a decline with increasing doses. Biochemical parameters showed dose-dependent responses, with low to moderate doses (1-3 Gy) stimulating enzyme activities and high doses (5 Gy) inhibiting them. Gene expression analysis was focused on the following specific genes: thymol synthase, γ-terpinene synthase, and carvacrol synthase. Low to moderate doses increased the expression of these genes, resulting in increased production of bioactive compounds. However, higher doses had diminished effects or suppressed gene expression. Metabolite analysis demonstrated dose-dependent responses, with moderate doses enhancing secondary metabolite production, while higher doses provided limited benefits. These findings underscore the implications of using gamma radiation to enhance secondary metabolite production in plants and its potential applications in agriculture, medicine, and environmental science. The study emphasizes the potential of gamma radiation as an external stressor to influence plant responses and highlights the importance of understanding such effects in various fields.

Creating a novel genetic diversity of Trichoderma afroharzianum by γ-radiation for xylanase-cellulase production.

Creating novel sources of a microbial strain using induced mutation can increase enzyme production for industrial use. According to this, we have developed a mutant strain of Trichoderma afroharzianum by Co60 gamma irradiation. Trichoderma mutants were isolated from an optimum dose of 250 Gy. The qualitative and quantitative screening were used for evaluating their enzyme production and the DNA barcoding method was used to identify the best Trichoderma mutant isolates. The highest cellulase (exo-glucanase, endoglucanase, ß-glucosidase, and total cellulase) and xylanase activities were observed in superior mutant isolates of Trichoderma afroharzianum NAS107-M44 and Trichoderma afroharzianum NAS107-M82, which is approximately 1.6-2.5 times higher than its parent strain, respectively. The electrophoretic pattern of proteins showed that the exo-glucanase I, endo-glucanase III, and the xylanase I enzymes hydrolyzed the corn bran, synergistically. Overall, gamma irradiation-induced mutation could be an expedient technique to access such superior mutants for the bioconversion of corn bran wastes.

Use of X-Irradiations in Reducing the Waste of Aflatoxin-Contaminated Pistachios and Evaluation of the Physicochemical Properties of the Irradiated Product.

This study investigates the effects of electron beam irradiation (0, 1, 2, 4, and 6 kGy) on Aspergillus flavus, aflatoxin B1 (AFB1), and the physicochemical properties of pistachios. The findings suggested that e-beam significantly reduced the spore population of A. flavus and the concentration of AFB1 at doses of 4 and 6 kGy. Three AFB1 degradation products were detected via LC-MS analysis and their structures were presented. Total phenolic content was improved at a dose of 2 kGy, while antioxidant activity was decreased in all treatments in both DPPH and ABTS assays. The chlorophyll and carotenoid content declined and the color indices changed, leading to a darker color. E-beam at a dose of 2 kGy raised the soluble protein levels and changed the intensity and pattern of protein bands. Irradiation doses of up to 6 kGy enhanced the content of malondialdehyde and total saturated fatty acids while leading to a decline in unsaturated fatty acids. The quality features were adversely affected at doses > 4 kGy. The findings suggest that as an alternative method, e-beam at doses ≥ 2 kGy can effectively decrease fungal load and aflatoxin B1 contamination, and e-beam application at doses ≤ 2 kGy can maintain the physicochemical attributes of pistachios to an acceptable extent.

Trichoderma harzianum as fungicide and symbiont: is it safe for human and animals?

Trichoderma species are considered as biological control agents against numerous phytopathogenic fungi. They are also helpful for plants as plant symbiont. This study aimed to identify harmful effects of Trichoderma in laboratory animals. In the first step, inhalation toxicity was studied. Six rats as control received a spray of bio-formulation without spores. Ten rats as treatment A received    1.00 × 106 colony-forming unit (CFU) of Trichoderma spores and ten rats as treatment B received 1.00 × 107 CFU per test of Trichoderma spores. The harmful effects of Trichoderma were obvious especially in the lungs, liver and kidney, and some blood parameters were abnormal. In the second step, we studied acute oral toxicity by gavage. Four rats as control received bio-formulation without spores. Six rats as treatment A received 1.00 × 106 CFU per test of Trichoderma spores. Six rats as treatment B received 1.00 × 107 CFU per test of Trichoderma spores. The harmful effects of Trichoderma were noticeable more in the liver and kidney tissues. For dermal toxicity study, two rabbits as control received bio-formulation without spores by rubbing on the surface of the skin. Treatment groups A and B received 1.00 × 106 and 1.00 × 107 CFU per test of Trichoderma spores, respectively (four rabbits for each group). The liver and kidney and some blood parameters were abnormal. Trichoderma has some harmful effects on tissues and organs and although it is a natural product, it should be used under cautions.

The Role of Cell Wall Degrading Enzymes in Antagonistic Traits of Trichoderma virens Against Rhizoctonia solani.

BACKGROUND: High antagonistic ability of different Trichoderma species against a diverse range of plant pathogenic fungi has led them to be used as a biological fungicide in agriculture. They can also promote plant growth, fertility, resistance to stress, and absorption of nutrients. They are also opportunistic and symbiotic pathogens, which can lead to the activation of plant defense mechanisms. OBJECTIVES: The aim of this present study was to investigate possible enhancement of lytic enzymes production and biocontrol activity of T. virens against Rhizoctonia solani through gamma radiation and to find the relationship between changes in lytic enzyme production and antagonistic activity of T. virens. MATERIAL AND METHODS: Dual culture conditions were used to evaluate the antagonistic effect of T. virens and its gamma mutants against R. solani. Then, their chitinase and cellulase activities were measured. For more detailed investigation of enzymes, densitometry pattern of the proteins was extracted from the T. virens wild-type and its mutants were obtained via SDS-polyacrylamide gel electrophoresis. RESULTS: The mutant T.vi M8, T. virens wild-type and mutant T.vi M20 strains showed the maximum antagonistic effects against the pathogen, respectively. Data showed that the mutant T. vi M8 reduced the growth of R. solani by 58 %. The mutants revealed significantly different (p<0.05) protein contents, chitinase and cellulase production (mg.mL-1) and activity (U.mL-1) compared to the wild-type strain. The highest extracellular protein production in the supernatant of chitinase and cellulase TFM was observed for the T.vi M11 and T.vi M17 strains, respectively. The T.vi M12 and wild-type strains secreted chitinase and cellulase significantly more than other strains did. Densitometry of SDS-PAGE gel bands indicated that both the amount and diversity of chitinase related proteins in the selected mutant (T. vi M8) were far higher than those of the wild-type. The diversity of molecular weight of proteins extracted from the T. virens M8 (20 proteins or bands) was very high compared to the wild-type (10 proteins) and mutant T.vi M15 (2 proteins). CONCLUSIONS: Overall, there was a strong link between the diversity of various chitinase proteins and the antagonistic properties of the mutant M8.

Biocontrol Activities of Gamma Induced Mutants of Trichoderma harzianum against some Soilborne Fungal Pathogens and their DNA Fingerprinting.

BACKGROUND: Random induced mutation by gamma radiation is one of the genetic manipulation strategies to improve the antagonistic ability of biocontrol agents. OBJECTIVES: This study aimed to induce mutants with more sporulation, colonization rate leading to enhanced antagonistic ability (in vitro assay) comparing to wild type (WT) and the assessment of genetic differences (in situ evaluation) using molecular markers. The superior mutants could be appropriate biocontrol agents against soil borne fungal diseases. MATERIALS AND METHODS: In this research sampling and isolation of Trichoderma isolates were performed from soils with low incidence of soil borne disease. T. harzianum 65 was selected and irradiation was conducted with gammacell at optimal dose 250 Gray/s. Mutants (115) were obtained from the WT. The antagonistic abilities of twenty-four mutants were evaluated using dual culture and culture filtrate tests. RESULTS: The results of in vitro assays revealed that Th15, Th11 and Th1 mutants exhibited stronger growth inhibition (GI) and colonization rate on Macrophomina phaseolina and Rhizoctonia solani AG4 compared to the wild type. Th15 and Th11 mutants exhibited stronger GI and colonization rate on Sclerotinia sclerotiorum in dual culture and culture filtrate tests and Th1 and Th11 mutants exhibited stronger GI on Fusarium grminearum in culture filtrate test. The DNA fingerprinting was carried out using RAPD and rep-PCR markers. Two (Th9 and Th17) out of the 24 mutants categorized distantly from the rest based on different polymorphism obtained by molecular markers. However, Th9 was different in GI% from Th17. RAPD analysis separated WT from mutants, Th9 from Th17 and also phenotypically superior mutants from other mutants. Meanwhile, rep-PCR analysis categorized WT isolate and mutants according to their antagonistic properties. CONCLUSIONS: The latter marker (rep-PCR) appeared to be reproducible and simple to distinguish mutants from a single isolate of T. harzianum. Mutants (3 isolates) were phenotypically and genotypically distinct from WT. These mutants demonstrated a pronounced biocontrol activities against soilborne fungal phytopathogens.