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. 2014 May 13:14:130.
doi: 10.1186/1471-2229-14-130.

Natural rice rhizospheric microbes suppress rice blast infections

Carla Spence, Emily Alff, Cameron Johnson, Cassandra Ramos, Nicole Donofrio, Venkatesan Sundaresan, Harsh Bais  1
Affiliations

Natural rice rhizospheric microbes suppress rice blast infections

"VSports手机版" Carla Spence et al. BMC Plant Biol. .

Abstract (VSports注册入口)

Background: The natural interactions between plant roots and their rhizospheric microbiome are vital to plant fitness, modulating both growth promotion and disease suppression VSports手机版. In rice (Oryza sativa), a globally important food crop, as much as 30% of yields are lost due to blast disease caused by fungal pathogen Magnaporthe oryzae. Capitalizing on the abilities of naturally occurring rice soil bacteria to reduce M. oryzae infections could provide a sustainable solution to reduce the amount of crops lost to blast disease. .

Results: Naturally occurring root-associated rhizospheric bacteria were isolated from California field grown rice plants (M-104), eleven of which were taxonomically identified by 16S rRNA gene sequencing and fatty acid methyl ester (FAME) analysis V体育安卓版. Bacterial isolates were tested for biocontrol activity against the devastating foliar rice fungal pathogen, M. oryzae pathovar 70-15. In vitro, a Pseudomonas isolate, EA105, displayed antibiosis through reducing appressoria formation by nearly 90% as well as directly inhibiting fungal growth by 76%. Although hydrogen cyanide (HCN) is a volatile commonly produced by biocontrol pseudomonads, the activity of EA105 seems to be independent of its HCN production. During in planta experiments, EA105 reduced the number of blast lesions formed by 33% and Pantoea agglomerans isolate, EA106 by 46%. Our data also show both EA105 and EA106 trigger jasmonic acid (JA) and ethylene (ET) dependent induced systemic resistance (ISR) response in rice. .

Conclusions: Out of 11 bacteria isolated from rice soil, pseudomonad EA105 most effectively inhibited the growth and appressoria formation of M. oryzae through a mechanism that is independent of cyanide production V体育ios版. In addition to direct antagonism, EA105 also appears to trigger ISR in rice plants through a mechanism that is dependent on JA and ET signaling, ultimately resulting in fewer blast lesions. The application of native bacteria as biocontrol agents in combination with current disease protection strategies could aid in global food security. .

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Figures

Figure 1
Figure 1
Relative abundance (frequency) of the major bacterial phyla present in the rice rhizosphere microbial community recorder over two-years. The frequencies shown were obtained via classification of 16S rDNA sequences corresponding to a total of 654 and 630 clones, for 2008 and 2009 respectively.
Figure 2
Figure 2
Inhibition of M. oryzae vegetative growth by rice soil isolates. A) Antimicrobial assay showing the degree of inhibition of M. oryzae 70–15 by naturally isolated rice rhizobacteria as well as P. fluorescens CHAO and cyanide mutant CHA77. Error bars indicate standard error. Different letters indicate statistically significant differences between treatments (Tukey’s HSD). B) Representative images of the fungal inhibitory effect seen when 70–15 was exposed to bacterial diffusible and volatile compounds (diffusible plates), or solely through volatile compounds (volatile plates).
Figure 3
Figure 3
Cyanide production by rice isolates and activity of cyanide mutant D5 against M. oryzae. A) Bacterial cyanide production of all rice isolates, D5, CHAO, and CHA77 was measured after 24 hour incubation using the Lazar Model LIS-146CNCM micro cyanide ion electrode. Different letters indicate statistical significance (Tukey’s HSD). B) Antimicrobial assay against M. oryzae strain 70–15 and its parental strain guy11 with EA105 and its cyanide deficient mutant, D5. Different letters indicate statistical significance (Tukey’s HSD).
Figure 4
Figure 4
Inhibition of M. oryzae appressoria after bacterial treatment. Effect of bacteria on M. oryzae 70–15 appressorial formation through A) direct bacterial treatment, or through B) indirect (or volatile) bacterial treatment. Germinated conidia were incubated in a 50uL drop with bacterial treatment (EA105, cyanide mutant D5, CHAO, cyanide mutant CHA77, or E. coli DH5α) or placed in a drop next to the bacterial treatment for the indirect assay. Error bars represent standard deviation. Different letters indicate a significant difference (Tukey’s HSD).
Figure 5
Figure 5
Activity of EA105 against naturally isolated phytopathogens. Inhibition of naturally isolated phytopathogens by EA105 and CHAO in comparison to M. oryzae. With the exception of lab strain F. oxysporum FO5, all pathogens were isolated from infected plants or soil, and acquired from Nancy Gregory at the University of Delaware. Error bars represent standard error. Asterisks indicate significant differences between EA105 and CHAO treatment (Student’s t-test, p < 0.05).
Figure 6
Figure 6
The effect of rhizobacterial priming on rice blast lesion formation. Spores were sprayed on 3-week old whole plants 24 hour after being root primed with mock, EA105, EA106, EA201 or CHAO suspension. A) Representative leaf segments of mock or rhizobacterial primed plants. B) The average number of lesions formed on the second youngest leaf of O. sativa cv. Maratelli. Error bars indicate standard error. Means with the same letter do not differ significantly (Tukey’s HSD).
Figure 7
Figure 7
Expression of defense related genes in rice plants treated with rhizobacteria EA105 and EA106. Roots of aseptically grown rice plants were treated with EA105 or EA106. Leaf samples were collected at 24 hrs post treatment and the expression of genes involved in A) ethylene, B) jasmonic acid (JA), or C) salicylic acid (SA) signaling was examined. Error bars indicate standard error. Means with the same letter do not differ significantly (Tukey’s HSD).
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References

    1. Zeigler RS, Leong SA, Teng PS. Rice blast disease. Rice Blast Disease. 1994. pp. 1–626.
    1. Skamnioti P, Gurr SJ. Against the grain: safeguarding rice from rice blast disease. Trends Biotechnol. 2009;27:141–150. doi: 10.1016/j.tibtech.2008.12.002. - DOI - PubMed
    1. Bonman JM, Khush GS, Nelson RJ. Breeding rice for resistance to pests. Annu Rev Phytopathol. 1992;30:507–528. doi: 10.1146/annurev.py.30.090192.002451. - DOI
    1. Chuma I, Isobe C, Hotta Y, Ibaragi K, Futamata N, Kusaba M, Yoshida K, Terauchi R, Fujita Y, Nakayashiki H, Valent B, Tosa Y. Multiple translocation of the AVR-Pita effector gene among chromosomes of the rice blast fungus Magnaporthe oryzae and related species. PLoS Pathogens. 2011;7:e1002147. doi: 10.1371/journal.ppat.1002147. - DOI - PMC - PubMed
    1. Aktar MW, Sengupta D, Chowdhury A. Impact of pesticides use in agriculture: their benefits and hazards. Interdisciplinary Toxicol. 2009;2:1–12. - PMC - PubMed

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