Mechanisms of Trichoderma longibrachiatum T6 Fermentation against Valsa mali through Inhibiting Its Growth and Reproduction, Pathogenicity and Gene Expression.

Apple Valsa canker is one of the most serious diseases, having caused significant apple yield and economic loss in China. However, there is still no effective biological methods for controlling this disease. Our present study focused on the inhibitory activity and mechanisms of Trichoderma longibrachiatum (T6) fermentation on Valsa mali that causes apple Valsa canker (AVC). Our results showed that the T6 fermentation exhibited effective antifungal activity on the mycelial growth and conidia germination of V. mali, causing mycelium malformation and the hyphal disintegrating in comparison to the control. The activity of pathogenically related enzymes that are secreted from V. mali and the expression level of gene of V. mali were significantly inhibited and downregulated by treatment with T6 fermentation. In addition, the lesion area and number of pycnidia of V. mali formed on the branches were significantly reduced after treatment with the T6 fermentation through the pathogenicity test on the detached branches. Our results indicate that the possible mechanism of T6 fermentation against V. mali occurs through inhibiting its growth and reproduction, the pathogenic enzyme activity, and its related gene expression.

Mycobiota of maize seeds revealed by rDNA-ITS sequence analysis of samples with varying storage times.

Fungi are an integral component of the plant microbiome. However, the composition and variation in the fungal communities (mycobiota) associated with seeds are poorly understood. In this study, we investigated the mycobiota of 11 maize seed samples with storage times ranging from 6 months to 12 years. Mycobiota were characterized by a culture-based approach, and fungal species were identified through rDNA-ITS sequence analyses. From a total of 169 pure fungal isolates obtained from both the seed surface and internal tissues, we identified 16 distinct species (belonging to 10 genera) associated with maize seeds, all but one of which were ascomycetes. Among these species, seven were exclusively isolated from internal tissues, two species were isolated only from the seed surface, and another six species were isolated from both the surface and internal tissues. Aspergillus niger was consistently found under all storage conditions and dominated fungal communities with a relative abundance of 36%-100%. Species of Fusarium (9%-40%) and Penicillium (9%-20%) were also frequently isolated, but other species appeared sporadically and were isolated from fewer than three seed stocks. According to our results, while the overall incidence of fungal infection generally declined with storage time, there was no consistent association between seed storage time and fungal species richness or relative abundance; furthermore, the composition of the mycobiota associated with maize seeds was highly variable among the samples. The detection of the four major mycotoxigenic fungal genera, specifically Aspergillus, Fusarium, Penicillium, and Alternaria, was alarming, and the isolation of a potential controlling agent as well as information about their temporal occurrence will contribute to the management of mycotoxins in the future.

[Efficiency of Trichoderma longibrachiatum T6 in the control of Meloidogyne incognita and its rhizosphere colonization in cucumber].

Efficiency of different concentrations of Trichoderma longibrachiatum T6 against Meloidogyne incognita and its rhizosphere colonization in cucumber were determined in greenhouse experiments. The results of rhizosphere colonization experiments showed that the number of colonies in cucumber soil and root increased significantly ten weeks after inoculation with the second stage juveniles of M. incognita and different concentrations of T. longibrachiatum T6, and there was significant difference in different concentrations of T. longibrachiatum T6, e.g., the maximum numbers of colonies in soil and root were 7.8 x 107 and 6.3 x 105 CFU · mL⁻¹ respectively after treated with the spore suspension of 1.5 x 107 CFU · mL⁻¹. Greenhouse experiments results showed that different concentrations of T. longibrachiatum T6 had significant control effect on different life stages of M. incognita, and the control effect increased with the concentration of T. longibrachiatum T6. T. longibrachiatum T6 significantly increased plant height, root length, above-ground and root fresh mass o cucumber inoculated by M. incognita. T. longibrachiatum T6 could colonize in cucumber rhizosphere, had control effect on M. incognita, and significantly improved the growth of cucumber.

[Screening, identification and biocontrol effect of antagonistic actinomycetes against the pathogen of Cytospora sp. for apple tree]. / è‹¹æžœæ ‘è çƒ‚ç— èŒæ‹®æŠ—æ”¾çº¿èŒçš„ç­›é€‰ã€é‰´å®šåŠé˜²æ•ˆ.

The pathogen of Cytospora sp. was considered as the target fungus to evaluate the bio-control potential of antagonistic actinomycetes against Cytospora sp. in the present study, which was isolated from the rhizosphere soil of apple tree. Moreover, the antagonistic effect of actinomycetes against Cytospora sp. growth was determined by the method of confrontation and growth rate, and the screened antagonistic strain was identified by the method of morphology and molecular biology. Also, the inhibitory activity of strain ZZ-9 against the conidium germination and mycelia growth of Cytospora sp. was determined in vivo, and its bio-control effect on Cytospora sp. growth was determined in detached apple twigs. The results showed that fifteen strains of actinomycetes had the inhibitory effect on Cytospora sp. growth, among all the isolated strains, which accounted for 18.8% and especially the inhibitory rate of eight strains was more than 50%. In addition, among all the screened strains, the strain ZZ-9 presented the highest inhibitory rate of 96.4%, which was significantly higher than those of the other isolated strains. The strain ZZ-9 was initially identified as Streptomyces rochei according to cultural characteristics, physiological and biochemical properties and 16S rDNA analysis. The nucleotide sequences in GenBank accession number was registered as KT986228. Different dilution of ZZ-9 fermentation had significant inhibitory effect on Cytospora sp. conidium germination and mycelia growth. The inhibitory rates of the 50 times fermentation on both conidium germination and mycelia growth were more than 80%. The inhibited mycelia's color was deepened, the mycelia branches were increased, and the ends of hyphae were swelled and deformed, even the protoplasm was concentrated and released. The bio-control effect of the ZZ-9 stock solution on Cytospora sp. growth was more than 75% in detached apple twigs. Thus, our results indicated that the strain ZZ-9 could be used for controlling apple tree Valsa canker in vivo and vitro.

[Lethal effects of Trichoderma longibrachiatum on Heterodera avenae].

The lethal effect of the conidia suspension of Trichoderma longibrachiatum against second stage juveniles of Heterodera avenae was observed under microscopic conditions and studied in vitro to preliminarily determine the potential and mechanism of the conidia suspension of T. longibrachiatum against H. avenae. Microscopic observation results showed that the conidia suspension of T. longibrachiatum adhered to or parasitized on the surface of second stage juveniles, even some parasitized nematodes were deformed at the initial stage. Later, the second stage juveniles were wrapped and the integuments were penetrated by a large number of hyphae germinated from the conidia suspension of T. longibrachiatum. Even the body of dead second stage juveniles was completely lysed. In vitro studies showed that different concentrations (1.5 x 10(5)-1.5 x 10(7) cfu x mL(-1)) of T. longibrachiatum (conidia suspension) had strong lethal and parasitic effects on the second stage juveniles of H. avenae, and significant differences existed among the treatments with different concentrations of T. longibrachiatum. In addition, the lethal and parasitic effects increased with increasing the T. longibrachiatum concentration. The mortality and corrected mortality of the second stage juveniles treated with the concentrations of 1.5 x 10(7) cfu x mL(-1) were 91.3% and 90.4% after 72 hours, and the second stage juveniles were parasitized by 88.7% after 14 days. Therefore, the conidia suspension of T. longibrachiatum had a great lethal effect on H. avenae, and the strain could be considered as a potential bio-control agent against H. avenae.

[Parasitic and lethal effects of Trichoderma longibrachiatum on Heterodera avenae: microscopic observation and bioassay].

A laboratory experiment was conducted to study the parasitic and lethal effects of Trichoderma longibrachiatum conidia suspension on Heterodera avenae cysts. Different concentrations (1.5 x 10(5)-1.5 x 10(7) cfu x mL(-1)) of T. longibrachiatum conidia suspension had strong parasitic and lethal effects on H. avenae cysts, and the effects differed significantly among the different concentrations. When treated with the T. longibrachiatum conidia suspension at a concentration of 1.5 x 10(7) cfu x mL(-1), 96.7% of the H. avenae cysts were parasitized by the conidia at the 18th day, and the hatching rate of the cysts was inhibited by 91.2% at the 22nd day. The microscopic observation showed that at the initial parasitic stage, T. longibrachiatum conidia suspension adhered or parasitized on the cyst surface, germinated a large number of hyphae, and grew on the cyst surface, making the development of cyst embryo stopped and the contents in cysts flocculated, and even, some cysts started to deform, and small dark brown vacuoles formed on the cyst surface. At the later parasitic stage, the cysts were penetrated by dense mycelium, cysts were broken, their contents exosmosed, and the mycelium on the integument of some cysts produced conidiophores, on which, conidium were adhered or parasitized. It was considered that T. longibrachiatum could be used as a potential high-efficient bioagent to control the occurrence and damage of H. avenae.

External noise and feedback regulation: steady-state statistics of auto-regulatory genetic network.

The steady-state statistics of a single gene auto-regulatory genetic network with the additive external Gaussian white noises is investigated. The main result shows that the negative feedback will result in that the mRNA noise has a positive contribution to the protein noise, but the positive feedback will result in that the mRNA noise has a negative contribution to the protein noise. If there is no feed back, then the contribution of mRNA noise to protein noise is always positive. On the other hand, the analysis and numerical simulations of linear and nonlinear feedback show that it is possible that the negative feedback increases, but the positive feedback decreases, the protein noise.