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The plant growth-promoting fungi (PGPF) have long been known to improve plant growth and suppress plant diseases. The PGPF Penicillium viridicatum GP15-1 elicited plant growth and induced systemic resistance (ISR) in Arabidopsis thaliana against Pseudomonas syringae pv. tomato DC3000 ( Pst), leading to a restriction of pathogen growth and disease development. Examination of local and systemic genes indicated that GP15-1 did not modulate the expression of any of the tested defence-related marker genes involved in salicylic acid (SA), jasmonic acid (JA) and ethylene signalling pathways. Subsequent challenge of GP15-1-colonized plants with Pst bacterium primed Arabidopsis plants for enhanced activation of the JA-inducible Atvsp (vegetative storage protein) gene at a later stage of infection. To assess the contribution of different signalling pathways in GP15-1-elicited plant growth and ISR, Arabidopsis genotypes implicated in SA signalling expressing the nahG transgene (NahG) or carrying disruption in NPR1 ( npr1), JA signalling ( jar1) and ethylene signalling ( ein2) were tested. The GP15-1-induced plant growth and ISR were fully compromised in an ein2 mutation. Root colonization assay revealed that the inability of the ein2 mutant to express GP15-1-induced plant growth and ISR was not associated with reduced root colonization by GP15-1. In conclusion, our results demonstrate the ethylene signalling pathway is involved in plant growth promotion and ISR elicitation by the PGPF P. viridicatum GP15-1 in Arabidopsis. These results provide evidence that ethylene signalling has a substantial role in plant growth and disease resistance. [ABSTRACT FROM AUTHOR]

The effect of fan-forced wind on the severity and growth ofFusarium oxysporumf. sp.radicis-lycopersici(FORL) was examined in this study. The discoloration severity of the total root system was significantly reduced in plants treated with air blasting for 30 min at a wind speed of 4 m/s compared with the control. In addition, the number of colony-forming units of FORL per gram of fresh root weight was significantly reduced (p ≤ 0.05) in plants treated with air blasting at a wind speed of 4 m/s for 30 min, and the root extracts of these plants had a significantly lower production of FORL budding cells. Booster wind treatments significantly reduced the severity and growth of FORL compared with single and control treatments. Furthermore, RT-PCR analysis indicated that the expression of defense-related genes was induced in the leaves of seedlings treated with air blasting at a wind speed of 4 m/s. [ABSTRACT FROM AUTHOR]

Susceptible and resistant cultivars of cucumber (cv. Suyo and cv. Shogoin fushinari, respectively) were evaluated for induction of systemic resistance by plant growth-promoting fungal isolatesPhomasp. GS8-1 and nonsporulating fungus GU21-2 againstColletotrichum orbiculare. Reduction in anthracnose disease was assessed at regular intervals of 0, 3, 6, and 9 days after challenge inoculation. Activities of endochitinase,β-1,3-endoglucanase, peroxidase (PO), polyphenol oxidase, and phenylalanine ammonia lyase (PAL) were assayed at the above intervals, while the activities of exochitinase andβ-1,3-exogluconase were assayed at 9 days after challenge inoculation. The data showed that all the enzymes activities increased in plants treated with plant growth-promoting fungi (PGPF) compared with nontreated plants of both cultivars. The activities of endochitinase andβ-1,3-endoglucanase were highly increased in PGPF-induced plants than in nontreated plants of both cultivars at different time points. Activities of PO, polyphenol oxidase, and PAL also increased between 3 and 6 days due to inoculation with PGPF and decreased thereafter. The activity of PAL at 9 days in PGPF-induced plants was at the same level as that of nontreated plants of both cultivars. Results of this investigation suggest that PGPF-induced systemic resistance is associated with not only high increases in the activities of chitinase andβ-1,3-gluconases but also other plant defense-related enzymes such as PO, PPO, and PAL. Roles of other mechanisms rather than accumulation of defense-related enzymes in PGPF-mediated induced resistance in susceptible cultivars were demonstrated. [ABSTRACT FROM AUTHOR]

The influence of the interaction between Phoma sp. GS8-2 (GS8-2) and the arbuscular mycorrhizal fungus Glomus mosseae (Gm) on the development of soil-borne diseases, microbial population, and plant growth in cucumber, bentgrass and tomato plants was investigated under controlled conditions. The composite inoculation of GS8-2 and Gm yielded varied effects on suppression of symptoms of soil-borne pathogens depending on the host-pathogen combination involved. The GS8-2 + Gm had neutral effect in reducing damping-off disease of cucumber caused by Rhizoctonia solani AG-4 and the crown and root rot disease of tomato caused by Fusarium oxysporum f. sp. radicis-lycopersici ( Forl), but exacerbated the brown patch disease caused by R. solani AG2-2 in bentgrass. In tomato plants, Forl populations in the roots and rhizosphere were significantly reduced by GS8-2 + Gm. Results also show that the composite inoculation of GS8-2 and Gm resulted to a synergistic effect on the reduction of fungal and bacterial populations in roots and rhizosphere of the plants. Plant growth enhancement was due to the individual effect of GS8-2 or Gm but not their interaction. GS8-2 root colonization of cucumber and tomato plants decreased significantly in dual inoculated plants compared to plants inoculated with GS8-2 alone; while no significant differences were found in the Gm root colonization of the three plant species indicating that GS8-2 had no effect on Gm. [ABSTRACT FROM AUTHOR]

The culture filtrate (CF) from the plant growth-promoting fungus Phoma sp. GS8-1 was found to induce systemic resistance in Arabidopsis thaliana against the bacterial leaf speck pathogen Pseudomonas syringae pv. tomato DC3000 ( Pst), and the underlying mechanism was studied. Roots of A. thaliana were treated with CF from GS8-1, and plants expressed a clear resistance to subsequent Pst infection; disease severity was reduced, and proliferation of pathogen was suppressed. Various mutants of A. thaliana were used to test whether the CF induced resistance through one of the known signaling pathways: salicylic acid (SA), jasmonic acid (JA), and ethylene (ET). The CF was fully protective against Pst in Arabidopsis mutants jar1 and ein2 similar to wild-type plants. However, its efficacy was reduced in plants containing transgene NahG. Examination of systemic gene expression revealed that CF modulates the expression of SA-inducible PR-1, PR-2 and PR-5 genes, the JA/ET-inducible ChitB gene, and the ET-inducible Hel gene. Moreover, the expression of these genes was further enhanced upon subsequent stimulation after attack by Pst. Our data suggest that in addition to a partial requirement for SA, the signals JA and ET may also play a role in defense signaling in Arabidopsis. [ABSTRACT FROM AUTHOR]

Although a wealth of information is available regarding resistance induced by plant growth-promoting rhizobacteria (PGPR), not much is known about plant growth-promoting fungi (PGPF). Hence, the goal of the present research was to provide more information on this matter. In Arabidopsis thaliana L., root colonizing PGPF Penicillium sp. GP16-2 or its cell free filtrate (CF) elicited an induced systemic resistance (ISR) against infection by Pseudomonas syringae pv. tomato DC3000 ( Pst), leading to a restriction of pathogen growth and disease development. We demonstrate that signal transduction leading to GP16-2-mediated ISR requires responsiveness to JA and ET in a NPR1-dependent manner, while CF-mediated ISR shows dispensability of SA, JA, ET and NPR1-dependent signaling (at least individually). In addition, root colonization by GP16-2 is not associated with a direct effect on expression of known defense-related genes, but potentiates the activation of JA/ET-inducible ChitB, which only becomes apparent after infection by Pst. However, CF-mediated ISR was partly associated with the direct activation of marker genes responsive to both SA and JA/ET signaling pathways and partly associated with priming, leading to activation of JA-/ET-inducible ChitB and Hel genes. These suggest that CF may contain one or more elicitors that induce resistance by way where at least SA, JA and ET may play a role in defense signaling in Arabidopsis. Therefore, defense gene changes and underlying signaling pathways induced by Penicillium sp. GP16-2 root colonization and its CF application are not the same and only partially overlap. [ABSTRACT FROM AUTHOR]