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Induced systemic resistance against Botrytis cinerea by Micromonospora strains isolated from root nodules.

Martínez-Hidalgo P, García JM, Pozo MJ - Front Microbiol (2015)

Bottom Line: This induced systemic resistance, confirmed in different tomato cultivars, is long lasting.The defensive response of tomato plants inoculated with Micromonospora spp. differs from that of non-inoculated plants, showing a stronger induction of jasmonate-regulated defenses when the plant is challenged with a pathogen.The hypothesis of jasmonates playing a key role in this defense priming effect was confirmed using defense-impaired tomato mutants, since the JA-deficient line def1 was unable to display a long term induced resistance upon Micromonospora spp. inoculation.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Genetics, University of Salamanca Salamanca, Spain ; Unidad Asociada USAL-CSIC "Interacción Planta-Microorganismo" Salamanca, Spain.

ABSTRACT
Micromonospora is a Gram positive bacterium that can be isolated from nitrogen fixing nodules from healthy leguminous plants, where they could be beneficial to the plant. Their plant growth promoting activity in legume and non-legume plants has been previously demonstrated. The present study explores the ability of Micromonospora strains to control fungal pathogens and to stimulate plant immunity. Micromonospora strains isolated from surface sterilized nodules of alfalfa showed in vitro antifungal activity against several pathogenic fungi. Moreover, root inoculation of tomato plants with these Micromonospora strains effectively reduced leaf infection by the fungal pathogen Botrytis cinerea, despite spatial separation between both microorganisms. This induced systemic resistance, confirmed in different tomato cultivars, is long lasting. Gene expression analyses evidenced that Micromonospora stimulates the plant capacity to activate defense mechanisms upon pathogen attack. The defensive response of tomato plants inoculated with Micromonospora spp. differs from that of non-inoculated plants, showing a stronger induction of jasmonate-regulated defenses when the plant is challenged with a pathogen. The hypothesis of jasmonates playing a key role in this defense priming effect was confirmed using defense-impaired tomato mutants, since the JA-deficient line def1 was unable to display a long term induced resistance upon Micromonospora spp. inoculation. In conclusion, nodule isolated Micromonospora strains should be considered excellent candidates as biocontrol agents as they combine both direct antifungal activity against plant pathogens and the ability to prime plant immunity.

No MeSH data available.


Related in: MedlinePlus

Effect of Micromonospora ALFpr18c root inoculation on B. cinerea disease development in different tomato cultivars (Solanum lycopersicom L. ‘Moneymaker’ and ‘Castlemart’). Necrosis severity caused by Botrytis was scored using a three levels disease scale: mild, moderate and severe, as shown in Supplementary Figure S2. The number of leaflets within each category is shown. For each tomato cultivar, disease damage level was compared between the control and the bacterial treatments. Control, plants not inoculated with Micromonospora; pr18c 1M and pr18c 1D, plants inoculated with Micromonospora sp. pr18c 1 month or 1 day before challenge with B. cinerea, respectively. Bars not sharing a common letter (lowercase for mild, uppercase for moderate and greek for severe symptoms) are significantly different using Bonferroni corrected Chi-square tests, followed by z-tests (P ≤ 0.05).
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Figure 2: Effect of Micromonospora ALFpr18c root inoculation on B. cinerea disease development in different tomato cultivars (Solanum lycopersicom L. ‘Moneymaker’ and ‘Castlemart’). Necrosis severity caused by Botrytis was scored using a three levels disease scale: mild, moderate and severe, as shown in Supplementary Figure S2. The number of leaflets within each category is shown. For each tomato cultivar, disease damage level was compared between the control and the bacterial treatments. Control, plants not inoculated with Micromonospora; pr18c 1M and pr18c 1D, plants inoculated with Micromonospora sp. pr18c 1 month or 1 day before challenge with B. cinerea, respectively. Bars not sharing a common letter (lowercase for mild, uppercase for moderate and greek for severe symptoms) are significantly different using Bonferroni corrected Chi-square tests, followed by z-tests (P ≤ 0.05).

Mentions: We extended our analysis to other tomato cultivars to find out if the protection by Micromonospora sp. ALFpr18c was a consistent effect for tomato and not a cultivar-specific response, choosing two well-characterized cultivars with defense impaired mutants available: ‘Castlemart’ and ‘Moneymaker.’ The sensitivity to B. cinerea of the two tomato cultivars differ significantly, being ‘Castlemart’ less severely affected than ‘Moneymaker’ (X2 = 18,871, P = 0.001; Figure 2). Remarkably, inoculation with Micromonospora spp. resulted in a significant reduction of the disease symptoms in both cultivars. The ISR by ALFpr18c against B. cinerea was effective regardless the timing of the inoculation of the bacteria, 30 days or 24 h before the challenge with the pathogen (Figure 2). Micromonospora sp. protected plants challenged with B. cinerea by reducing the severity of damage caused by the pathogen, as it was shown by a significant decrease in the number of leaflets with the highest level of damage (Figure 2). Indeed, there was a statistically significant association between levels of leaf fungal damage and inoculation treatments for ‘Castlemart’ (X2 = 8,374, P = 0.015) and for ‘Moneymaker’ (X2 = 29,824, P = 0.001).


Induced systemic resistance against Botrytis cinerea by Micromonospora strains isolated from root nodules.

Martínez-Hidalgo P, García JM, Pozo MJ - Front Microbiol (2015)

Effect of Micromonospora ALFpr18c root inoculation on B. cinerea disease development in different tomato cultivars (Solanum lycopersicom L. ‘Moneymaker’ and ‘Castlemart’). Necrosis severity caused by Botrytis was scored using a three levels disease scale: mild, moderate and severe, as shown in Supplementary Figure S2. The number of leaflets within each category is shown. For each tomato cultivar, disease damage level was compared between the control and the bacterial treatments. Control, plants not inoculated with Micromonospora; pr18c 1M and pr18c 1D, plants inoculated with Micromonospora sp. pr18c 1 month or 1 day before challenge with B. cinerea, respectively. Bars not sharing a common letter (lowercase for mild, uppercase for moderate and greek for severe symptoms) are significantly different using Bonferroni corrected Chi-square tests, followed by z-tests (P ≤ 0.05).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4556977&req=5

Figure 2: Effect of Micromonospora ALFpr18c root inoculation on B. cinerea disease development in different tomato cultivars (Solanum lycopersicom L. ‘Moneymaker’ and ‘Castlemart’). Necrosis severity caused by Botrytis was scored using a three levels disease scale: mild, moderate and severe, as shown in Supplementary Figure S2. The number of leaflets within each category is shown. For each tomato cultivar, disease damage level was compared between the control and the bacterial treatments. Control, plants not inoculated with Micromonospora; pr18c 1M and pr18c 1D, plants inoculated with Micromonospora sp. pr18c 1 month or 1 day before challenge with B. cinerea, respectively. Bars not sharing a common letter (lowercase for mild, uppercase for moderate and greek for severe symptoms) are significantly different using Bonferroni corrected Chi-square tests, followed by z-tests (P ≤ 0.05).
Mentions: We extended our analysis to other tomato cultivars to find out if the protection by Micromonospora sp. ALFpr18c was a consistent effect for tomato and not a cultivar-specific response, choosing two well-characterized cultivars with defense impaired mutants available: ‘Castlemart’ and ‘Moneymaker.’ The sensitivity to B. cinerea of the two tomato cultivars differ significantly, being ‘Castlemart’ less severely affected than ‘Moneymaker’ (X2 = 18,871, P = 0.001; Figure 2). Remarkably, inoculation with Micromonospora spp. resulted in a significant reduction of the disease symptoms in both cultivars. The ISR by ALFpr18c against B. cinerea was effective regardless the timing of the inoculation of the bacteria, 30 days or 24 h before the challenge with the pathogen (Figure 2). Micromonospora sp. protected plants challenged with B. cinerea by reducing the severity of damage caused by the pathogen, as it was shown by a significant decrease in the number of leaflets with the highest level of damage (Figure 2). Indeed, there was a statistically significant association between levels of leaf fungal damage and inoculation treatments for ‘Castlemart’ (X2 = 8,374, P = 0.015) and for ‘Moneymaker’ (X2 = 29,824, P = 0.001).

Bottom Line: This induced systemic resistance, confirmed in different tomato cultivars, is long lasting.The defensive response of tomato plants inoculated with Micromonospora spp. differs from that of non-inoculated plants, showing a stronger induction of jasmonate-regulated defenses when the plant is challenged with a pathogen.The hypothesis of jasmonates playing a key role in this defense priming effect was confirmed using defense-impaired tomato mutants, since the JA-deficient line def1 was unable to display a long term induced resistance upon Micromonospora spp. inoculation.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Genetics, University of Salamanca Salamanca, Spain ; Unidad Asociada USAL-CSIC "Interacción Planta-Microorganismo" Salamanca, Spain.

ABSTRACT
Micromonospora is a Gram positive bacterium that can be isolated from nitrogen fixing nodules from healthy leguminous plants, where they could be beneficial to the plant. Their plant growth promoting activity in legume and non-legume plants has been previously demonstrated. The present study explores the ability of Micromonospora strains to control fungal pathogens and to stimulate plant immunity. Micromonospora strains isolated from surface sterilized nodules of alfalfa showed in vitro antifungal activity against several pathogenic fungi. Moreover, root inoculation of tomato plants with these Micromonospora strains effectively reduced leaf infection by the fungal pathogen Botrytis cinerea, despite spatial separation between both microorganisms. This induced systemic resistance, confirmed in different tomato cultivars, is long lasting. Gene expression analyses evidenced that Micromonospora stimulates the plant capacity to activate defense mechanisms upon pathogen attack. The defensive response of tomato plants inoculated with Micromonospora spp. differs from that of non-inoculated plants, showing a stronger induction of jasmonate-regulated defenses when the plant is challenged with a pathogen. The hypothesis of jasmonates playing a key role in this defense priming effect was confirmed using defense-impaired tomato mutants, since the JA-deficient line def1 was unable to display a long term induced resistance upon Micromonospora spp. inoculation. In conclusion, nodule isolated Micromonospora strains should be considered excellent candidates as biocontrol agents as they combine both direct antifungal activity against plant pathogens and the ability to prime plant immunity.

No MeSH data available.


Related in: MedlinePlus