scholarly journals INTERFERENCE BY NON-HOST PLANT ROOTS AND ROOT EXUDATES IN THE INFECTION PROCESSES OF <I>PHYTOPHTHORA NICOTIANAE</I>

2021 ◽  
Vol 0 (0) ◽  
pp. 0
Keyword(s):  
Host Plant ◽  
Root Exudates ◽  
Phytophthora Nicotianae ◽  
Plant Roots ◽  
Infection Processes

scholarly journals Rootstock-Scion Interaction Affects the Composition and Pathogen Inhibitory Activity of Tobacco (Nicotiana tabacum L.) Root Exudates

Plants ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 1652
Author(s):  
Cheng-Sheng Zhang ◽  
Yanfen Zheng ◽  
Lijuan Peng ◽  
Jianmin Cao
Keyword(s):  
Nicotiana Tabacum ◽  
Root Exudates ◽  
Root Exudate ◽  
Phytophthora Nicotianae ◽  
Susceptible Cultivar ◽  
Black Shank ◽  
Nicotiana Tabacum L ◽  
Disease Induction ◽  
Resistant Rootstock ◽  
Ethylhexyl Phthalate

The composition and allelopathy to Phytophthora nicotianae (the causal agent of tobacco black shank disease) of root exudates from a resistant tobacco (Nicotiana tabacum L.) cultivar Gexin 3, a susceptible cultivar Xiaohuangjin 1025 and their reciprocal grafts were investigated. Grafting with disease-resistant rootstock could improve resistance to black shank; this is closely related to the allelopathy of root exudates. The root exudates from the resistant cultivar inhibited the growth of P. nicotianae, while those from the susceptible cultivar promoted the growth; the grafting varieties had intermediate properties. The root exudate composition differed among cultivars. Gexin 3 was rich in esters and fatty acids, while Xiaohuangjin 1025 contained more hydrocarbons and phenolic acids. The composition of root exudates of grafted cultivars as well as their allelopathy to P. nicotianae were altered, and tended to be close to the composition of cultivar used as rootstock. Eugenol, 4-tert-butylphenol, mono (2-ethylhexyl) phthalate, 4-hydroxybenzoic acid, 2,6-di-tert-butylphenol, dipropyl phthalate, and methyl myristate were identified as the main compounds contributing to inhibitory properties of root exudates. Sorbitol was suggested to play a role in disease induction. Overall, rootstock–scion interaction affected the composition of tobacco root exudates, which may be attributed to the different disease resistance among grafted plants, rootstock and scion.

scholarly journals The Biocontrol Agent and Insect Pathogen Photorhabdus luminescens Interacts with Plant Roots

2020 ◽  
Vol 86 (17) ◽  
Author(s):  
Alice Regaiolo ◽  
Nazzareno Dominelli ◽  
Karsten Andresen ◽  
Ralf Heermann
Keyword(s):  
Biological Control ◽  
Pest Management ◽  
Root Exudates ◽  
Biological Control Agent ◽  
Plant Root ◽  
Specific Interaction ◽  
Plant Roots ◽  
Photorhabdus Luminescens ◽  
Content Type ◽  
Root Interactions

ABSTRACT The number of sustainable agriculture techniques to improve pest management and environmental safety is rising, as biological control agents are used to enhance disease resistance and abiotic stress tolerance in crops. Here, we investigated the capacity of the Photorhabdus luminescens secondary variant to react to plant root exudates and their behavior toward microorganisms in the rhizosphere. P. luminescens is known to live in symbiosis with entomopathogenic nematodes (EPNs) and to be highly pathogenic toward insects. The P. luminescens-EPN relationship has been widely studied, and this combination has been used as a biological control agent; however, not much attention has been paid to the putative lifestyle of P. luminescens in the rhizosphere. We performed transcriptome analysis to show how P. luminescens responds to plant root exudates. The analysis highlighted genes involved in chitin degradation, biofilm regulation, formation of flagella, and type VI secretion system. Furthermore, we provide evidence that P. luminescens can inhibit growth of phytopathogenic fungi. Finally, we demonstrated a specific interaction of P. luminescens with plant roots. Understanding the role and the function of this bacterium in the rhizosphere might accelerate the progress in biocontrol manipulation and elucidate the peculiar mechanisms adopted by plant growth-promoting rhizobacteria in plant root interactions. IMPORTANCE Insect-pathogenic Photorhabdus luminescens bacteria are widely used in biocontrol strategies against pests. Very little is known about the life of these bacteria in the rhizosphere. Here, we show that P. luminescens can specifically react to and interact with plant roots. Understanding the adaptation of P. luminescens in the rhizosphere is highly important for the biotechnological application of entomopathogenic bacteria and could improve future sustainable pest management in agriculture.

scholarly journals Investigating the role of root exudates in recruiting Streptomyces bacteria to the Arabidopsis thaliana root microbiome

2020 ◽  
Author(s):  
Sarah F. Worsley ◽  
Michael Macey ◽  
Sam Prudence ◽  
Barrie Wilkinson ◽  
J. Colin Murrell ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Stable Isotope ◽  
Plant Growth ◽  
Root Exudates ◽  
Soil Bacteria ◽  
Stable Isotope Probing ◽  
Plant Roots ◽  
Plant Metabolites ◽  
Complex Organic ◽  
Root Microbiome

AbstractStreptomyces species are saprophytic soil bacteria that produce a diverse array of specialised metabolites, including half of all known antibiotics. They are also rhizobacteria and plant endophytes that can promote plant growth and protect against disease. Several studies have shown that streptomycetes are enriched in the rhizosphere and endosphere of the model plant Arabidopsis thaliana. Here, we set out to test the hypothesis that they are attracted to plant roots by root exudates, and specifically by the plant phytohormone salicylate, which they might use as a nutrient source. We confirmed a previously published report that salicylate over-producing cpr5 plants are colonised more readily by streptomycetes but found that salicylate-deficient sid2-2 and pad4 plants had the same levels of root colonisation by Streptomyces bacteria as the wild-type plants. We then tested eight genome sequenced Streptomyces endophyte strains in vitro and found that none were attracted to or could grow on salicylate as a sole carbon source. We next used 13CO2 DNA stable isotope probing to test whether Streptomyces species can feed off a wider range of plant metabolites but found that Streptomyces bacteria were outcompeted by faster growing proteobacteria and did not incorporate photosynthetically fixed carbon into their DNA. We conclude that, given their saprotrophic nature and under conditions of high competition, streptomycetes most likely feed on more complex organic material shed by growing plant roots. Understanding the factors that impact the competitiveness of strains in the plant root microbiome could have consequences for the effective application of biocontrol strains.ImportanceStreptomyces bacteria are ubiquitous in soil but their role as rhizobacteria is less well studied. Our recent work demonstrated that streptomycetes isolated from A. thaliana roots can promote growth and protect against disease across plant species and that plant growth hormones can modulate the production of bioactive specialised metabolites by these strains. Here we used 13CO2 DNA stable isotope probing to identify which bacteria feed on plant metabolites in the A. thaliana rhizosphere and, for the first time, in the endosphere. We found that Streptomyces species are outcompeted for these metabolites by faster growing proteobacteria and instead likely subsist on more complex organic material such as cellulose derived from plant cell material that is shed from the roots. This work thus reveals the “winners and losers” in the battle between soil bacteria for plant metabolites and could inform the development of methods to apply streptomycetes as plant growth-promoting agents.

scholarly journals Phosphorus deficiency changes carbon isotope fractionation and triggers exudate reacquisition in tomato plants

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Raphael Tiziani ◽  
Youry Pii ◽  
Silvia Celletti ◽  
Stefano Cesco ◽  
Tanja Mimmo
Keyword(s):  
Root Exudates ◽  
Isotope Fractionation ◽  
Phosphorus Deficiency ◽  
Plant Roots ◽  
P Deficiency ◽  
Tomato Plants ◽  
Tomato Roots ◽  
Wide Range ◽  
Hydroponically Grown ◽  
Over Time

Abstract Plant roots are able to exude vast amounts of metabolites into the rhizosphere in response to phosphorus (P) deficiency. Causing noteworthy costs in terms of energy and carbon (C) for the plants. Therefore, it is suggested that exudates reacquisition by roots could represent an energy saving strategy of plants. This study aimed at investigating the effect of P deficiency on the ability of hydroponically grown tomato plants to re-acquire specific compounds generally present in root exudates by using 13C-labelled molecules. Results showed that P deficient tomato plants were able to take up citrate (+ 37%) and malate (+ 37%), particularly when compared to controls. While glycine (+ 42%) and fructose (+ 49%) uptake was enhanced in P shortage, glucose acquisition was not affected by the nutritional status. Unexpectedly, results also showed that P deficiency leads to a 13C enrichment in both tomato roots and shoots over time (shoots—+ 2.66‰, roots—+ 2.64‰, compared to control plants), probably due to stomata closure triggered by P deficiency. These findings highlight that tomato plants are able to take up a wide range of metabolites belonging to root exudates, thus maximizing C trade off. This trait is particularly evident when plants grew in P deficiency.

scholarly journals Community composition of arctic root-associated fungi mirrors host plant phylogeny

2020 ◽  
Vol 96 (11) ◽  
Author(s):  
S S Botnen ◽  
E Thoen ◽  
P B Eidesen ◽  
A K Krabberød ◽  
H Kauserud
Keyword(s):  
Host Plant ◽  
Community Composition ◽  
Plant Species ◽  
Host Plants ◽  
Plant Roots ◽  
Gene Marker ◽  
Rrna Gene ◽  
Phylogenetic Distance ◽  
Gene Markers ◽  
Plant Phylogeny

ABSTRACT The number of plant species regarded as non-mycorrhizal increases at higher latitudes, and several plant species in the High-Arctic Archipelago Svalbard have been reported as non-mycorrhizal. We used the rRNA ITS2 and 18S gene markers to survey which fungi, as well as other micro-eukaryotes, were associated with roots of 31 arctic plant species not usually regarded as mycorrhizal in Svalbard. We assessed to what degree the root-associated fungi showed any host preference and whether the phylogeny of the plant hosts may mirror the composition of root-associated fungi. Fungal communities were largely structured according to host plant identity and to a less extent by environmental factors. We observed a positive relationship between the phylogenetic distance of host plants and the distance of fungal community composition between samples, indicating that the evolutionary history of the host plants plays a major role for which fungi colonize the plant roots. In contrast to the ITS2 marker, the 18S rRNA gene marker showed that chytrid fungi were prevalently associated with plant roots, together with a wide spectrum of amoeba-like protists and nematodes. Our study confirms that arbuscular mycorrhizal (AM) fungi are present also in arctic environments in low abundance.

scholarly journals Imazapic Herbigation for Egyptian Broomrape (Phelipanche aegyptiaca) Control in Processing Tomatoes—Laboratory and Greenhouse Studies

Plants ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 1182
Author(s):  
Yaakov Goldwasser ◽  
Onn Rabinovitz ◽  
Zev Gerstl ◽  
Ahmed Nasser ◽  
Amit Paporisch ◽  
...  
Keyword(s):  
Host Plant ◽  
Drip Irrigation ◽  
High Rate ◽  
Plant Roots ◽  
Irrigation Systems ◽  
Vast Number ◽  
Tomato Roots ◽  
Wide Range ◽  
Heavy Damage ◽  
Processing Tomatoes

Parasitic plants belonging to the Orobanchaceae family include species that cause heavy damage to crops in Mediterranean climate regions. Phelipanche aegyptiaca is the most common of the Orobanchaceae species in Israel inflicting heavy damage to a wide range of broadleaf crops, including processing tomatoes. P. aegyptiaca is extremely difficult to control due to its minute and vast number of seeds and its underground association with host plant roots. The highly efficient attachment of the parasite haustoria into the host phloem and xylem enables the diversion of water, assimilates and minerals from the host into the parasite. Drip irrigation is the most common method of irrigation in processing tomatoes in Israel, but the delivery of herbicides via drip irrigation systems (herbigation) has not been thoroughly studied. The aim of these studies was to test, under laboratory and greenhouse conditions, the factors involved in the behavior of soil-herbigated imazapic, and the consequential influence of imazapic on P. aegyptiaca and tomato plants. Dose-response Petri dish studies showed that imazapic does not impede P. aegyptiaca seed germination and non-attached seedlings, even at the high rate of 5000 ppb. Imazapic applied to tomato roots inoculated with P. aegyptiaca seeds in a PE bag system revealed that the parasite is killed only after its attachment to the tomato roots, at concentrations as low as 2.5 ppb. Imazapic sorption curves and calculated Kd and Koc values indicated that the herbicide Kd is similar in all soils excluding a two-fold higher coefficient in the Gadash farm soil, while the Koc was similar in all soils except the Eden farm soil, in which it was more than twofold lower. In greenhouse studies, control of P. aegyptiaca was achieved at >2.5 ppb imazapic, but adequate control requires repeated applications due to the 7-day half-life (t1/2) of the herbicide in the soil. Tracking of imazapic in soil and tomato roots revealed that the herbicide accumulates in the tomato host plant roots, but its movement to newly formed roots is limited. The data obtained in the laboratory and greenhouse studies provide invaluable knowledge for devising field imazapic application strategies via drip irrigation systems for efficient and selective broomrape control.

scholarly journals Investigating the Role of Root Exudates in Recruiting Streptomyces Bacteria to the Arabidopsis thaliana Microbiome

2021 ◽  
Vol 8 ◽  
Author(s):  
Sarah F. Worsley ◽  
Michael C. Macey ◽  
Samuel M. M. Prudence ◽  
Barrie Wilkinson ◽  
J. Colin Murrell ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Root Exudates ◽  
Plant Root ◽  
Stable Isotope Probing ◽  
Plant Roots ◽  
Plant Metabolites ◽  
Published Report ◽  
Promote Plant Growth

Streptomyces species are saprophytic soil bacteria that produce a diverse array of specialized metabolites, including half of all known antibiotics. They are also rhizobacteria and plant endophytes that can promote plant growth and protect against disease. Several studies have shown that streptomycetes are enriched in the rhizosphere and endosphere of the model plant Arabidopsis thaliana. Here, we set out to test the hypothesis that they are attracted to plant roots by root exudates, and specifically by the plant phytohormone salicylate, which they might use as a nutrient source. We confirmed a previously published report that salicylate over-producing cpr5 plants are colonized more readily by streptomycetes but found that salicylate-deficient sid2-2 and pad4 plants had the same levels of root colonization by Streptomyces bacteria as the wild-type plants. We then tested eight genome sequenced Streptomyces endophyte strains in vitro and found that none were attracted to or could grow on salicylate as a sole carbon source. We next used 13CO2 DNA stable isotope probing to test whether Streptomyces species can feed off a wider range of plant metabolites but found that Streptomyces bacteria were outcompeted by faster growing proteobacteria and did not incorporate photosynthetically fixed carbon into their DNA. We conclude that, given their saprotrophic nature and under conditions of high competition, streptomycetes most likely feed on more complex organic material shed by growing plant roots. Understanding the factors that impact the competitiveness of strains in the plant root microbiome could have consequences for the effective application of biocontrol strains.

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