Project description:Biological control is a promising approach to control diseases caused by Pythium species. Unusually for a single genus, the Pythium genus also includes species that can antagonise Pythium plant pathogens, such as Pythium oligandrum. These Pythium plant pathogens are commonly found in the soil such as the broad host-range pathogen Pythium myriotylum and cause various diseases of important crops. While P. oligandrum genes expressed in the interaction with oomycete plant pathogens have been identified previously, the transcriptional response of an oomycete plant pathogen to P. oligandrum has not been investigated. An isolate of P. oligandrum, GAQ1, recovered from soil could antagonise P. myriotylum in a plate-based confrontation assay. The P. oligandrum isolate had a strong disease control effect on soft-rot of ginger caused by P. myriotylum. We investigated the transcriptional interaction between P. myriotylum and P. oligandrum. As part of the transcriptional response of P. myriotylum to the presence of P. oligandrum, putative effector genes such as a sub-set of Kazal-type protease inhibitors were strongly upregulated. P. myriotylum cellulases and elicitin-like putative effectors were also upregulated. In P. oligandrum, cellulases, peroxidases, proteases and NLP effectors were upregulated. The transcriptional response of P. myriotylum suggests clear features of a counter-attacking strategy that may contribute to the variable success and durability of biological attempts to control diseases caused by Pythium species. Whether aspects of this counter-attack could inhibit aspects of this virulence of P. myriotylum is another interesting aspect for future studies.
Project description:The oomycete Pythium oligandrum is a potential biocontrol agent to control a wide range of fungal and oomycetes-caused diseases such as Pythium myriotylum-caused rhizome rot in ginger leading to reduced yields and compromised quality. Previously, P. oligandrum has been studied for its plant growth-promoting potential by auxin production and induction of disease resistance by elicitors such as oligandrin. Volatile organic compounds (VOCs) play beneficial roles in sustainable agriculture by enhancing plant growth and resistance. We investigated the contribution of P. oligandrum-produced VOCs on plant growth and disease suppression by initially using N. benthamiana plants for screening. P. oligandrum VOCs significantly enhanced tobacco seedling and plant biomass content. Screening of the individual VOCs showed that 3-octanone and hexadecane promoted the growth of tobacco seedlings. The total VOCs from P. oligandrum also enhanced the shoot and root growth of ginger plants. Transcriptomic analysis showed a higher expression of genes related to plant growth hormones, and stress responses in the leaves of ginger plants exposed to P. oligandrum VOCs. The concentrations of plant growth hormones such as auxin, zeatin, and gibberellic acid were higher in the leaves of ginger plants exposed to P. oligandrum VOCs. In a ginger disease biocontrol assay, the VOC-exposed ginger plants infected with P. myriotylum had lower levels of disease severity. We conclude that this study contributes to understanding the growth-promoting mechanisms of P. oligandrum on ginger and tobacco, priming of ginger plants against various stress and the mechanisms of action of P. oligandrum as a biocontrol agent.
Project description:The biocontrol agent Pythium oligandrum, which is a member of phylum Oomycota, can control diseases caused by a taxonomically wide range of plant pathogens, including fungi, bacteria, and oomycetes. However, whether P. oligandrum could control diseases caused by plant root-knot nematodes (RKNs) was unknown. We investigated a recently isolated P. oligandrum strain GAQ1, and the P. oligandrum CBS530.74 strain, for the control of RKN Meloidogyne incognita infection of tomato (Solanum lycopersicum L.). Initially, P. oligandrum culture filtrates were found to be lethal to M. incognita second-stage juveniles (J2s) with up to 84% mortality at 24 h after treatment compared to 14% in the control group. Consistent with the lethality to M. incognita J2s, tomato roots treated with P. oligandrum culture filtrates reduced the attraction of nematodes, and the number of nematodes penetrating the roots was reduced by up to 78%. In a greenhouse pot trial, P. oligandrum GAQ1 inoculation of tomato plants significantly reduced the gall number by 58% in plants infected with M. incognita. Notably, P. oligandrum GAQ1 mycelial treatment significantly increased tomato plant height (by 36%), weight (by 27%), and root weight (by 48%). Transcriptome analysis of tomato seedling roots inoculated with the P. oligandrum GAQ1 strain identified ~2,500 differentially expressed genes. The enriched GO terms and annotations in the up-regulated genes suggested modulation of plant hormone-signaling and defense-related pathways in response to P. oligandrum. In conclusion, our results support that P. oligandrum GAQ1 can serve as a potential biocontrol agent for M. incognita control in tomato. Multiple mechanisms appear to contribute to the biocontrol effect involving direct inhibition of M. incognita, potential priming of tomato plant defenses, and plant growth promotion.
Project description:The objective of this study was to evaluate the effect of mycoparasite and roo tendophyte P. oligandrum on the A17 M. truncatula transcriptome.
Project description:The oomycete P. oligandrum is a soil-inhabiting parasite and predator of both fungi and oomycetes and uses hydrolytic enzymes extensively to penetrate and hydrolyze its host or prey. Other mechanisms have been overlooked, and we investigated whether P. oligandrum-produced volatile organic compounds (VOCs) could also be contributing to antagonism. VOCs have diverse functions, including contributing to antagonism in ecological interactions and potential applications in biocontrol. The growth-inhibiting activity of P. oligandrum VOCs was tested on P. myriotylum – a host or prey of P. oligandrum – coupled with electron microscopy, biochemical assays and transcriptomic analysis. The total VOCs produced by P. oligandrum reduced P. myriotylum growth by 80% and zoospore levels by 60%. GC-MS identified twenty-three VOCs, and methyl heptenone, D-limonene, 2-undecanone and 1-octanal were potent inhibitors of P. myriotylum growth and led to increased production of reactive oxygen species at a concentration that did not inhibit P. oligandrum growth. Exposure to the total VOCs of P. oligandrum led to shrinkage of P. myriotylum hyphae, and lysis of the cellular membranes and organelles. Transcriptomic analysis of P. myriotylum exposed to the P. oligandrum VOCs at increasing levels of growth inhibition showed initially a strong upregulation of putative detoxification related genes that was not maintained later during exposure to the VOCs. The inhibition of P. myriotylum growth continued after the exposure to the VOCs was discontinued and led to reduced leaf lesion size during P. myriotylum infection of its plant host. The VOCs produced by P. oligandrum could be another factor alongside hydrolytic enzymes contributing to its ecological role as a microbial antagonist where the concentration of the VOCs may be inhibitory in particular ecological niches such as in soil. The VOCs analyzed here may also be contributing to the biocontrol of diseases using P. oligandrum commercial preparations.