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Induced Systemic Resistance and Promotion of Plant Growth by Bacillus spp…
Induced Systemic Resistance and Promotion of Plant Growth by Bacillus spp.
штаммы
B. amyloliquefaciens, B. subtilis, B. pasteurii, B. cereus, B. pumilus, B. mycoides, B. sphaericus
Greenhouse reports of systemic disease protection
2 strains of
B. pumilus
(strains 203-6 and 203-7) and 1 of
B. mycoides
(strain Bac J)
reduced the severity of Cercospora leaf spot of sugar beet (Cercospora beticola)
Bac J
strain was sprayed onto one leaf of test plants at approximately
1.0 log 8 CFU/ml
The leaf was bagged, and the plants were challenge-inoculated by being sprayed with spore suspensions 3 days after treatment with Bac J
Significant reductions in disease severity were obtained by treatment with Bac J on both a highly susceptible and a moderately resistant variety of sugar
Strains 203-6 and 203-7
, originating from sugar beet embryos, were selected in a subsequent study aimed at developing a rapid selection system for bacteria that elicit ISR against Cercospora leaf spot
Both strains significantly reduced disease severity to a level that was not significantly different from the protection afforded by strain Bac J and
acibenzolar-S-methyl
, a chemical elicitor of systemic acquired resistance
Bacillus spp
Bacillus spp. Zehnder et al. (35)
against Cucumber mosaic virus (CMV)
When compared with controls, all the bacterial treatments significantly reduced disease severity based on symptoms, decreased disease incidence based on enzyme-linked immunosorbent assay (ELISA), and decreased virus accumulation
Elicitation of systemic protection against CMV by B. pumilus strain SE34 was also noted in tobacco in unpublished work by C.-M. Ryu.
The severity of blue mold of tobacco, caused by Peronospora tabacina Adam, has been reduced by treatment with Bacillus spp. (37–39).
B. pasteurii C-9 and B. pumilus SE34 and T4
, when applied as soil drenches of three tobacco cultivars, resulted in significant reductions in the mean percentage of leaf area with lesions caused by Peronospora tabacina.
Field reports of systemic disease protection
On sugar beet,
B. mycoides strain Bac J
, when sprayed onto leaves using a suspension of log 7.0 CFU/ml, significantly reduced the severity of Cercospora leaf spot on sugar beet in field trials conducted during six growing season
Mechanisms of ISR by Bacillus spp
It has been suggested that mixtures of PGPR strains with different mechanisms (22) might more reliably benefit plants than would individual PGPR strains :!:
Elicitation of ISR in sugar beet by B. mycoides strain Bac J (1) and B. pumilus strains 203-6 and 203-7 (2) was associated with
enhanced peroxidase activity
and
increased production of one chitinase isozyme and two isozymes of β-1,3-glucanase.
In the tobacco blue mold system, Zhang et al. (37) reported that plants treated with
B. pumilus strain SE34
had greatly increased levels of
salicylic acid
, compared with that of nontreated plants or plants treated with two gram-negative bacteria, 1 day after challenge-inoculation with the pathogen
Two
cytological studies
were conducted by Benhamou et al. (3,4) with
B. pumilus strain SE34.
1 -
treated with SE34
- colonization of pea roots by Fusarium oxysporum f. sp. pisi was restricted to the epidermis and outer cortex of roots
nonbacterized roots
, the pathogen extensively colonized the cortex, endodermis, and the paratracheal parenchyma cells and radiated toward the vascular stele
This reduction in fungal colonization by treatment with strain SE34 was associated
with strengthening of the epidermal and cortical cell walls.
In addition, roots treated with SE34 exhibited
newly formed barriers
beyond the site of fungal infection
These barriers were cell wall appositions that contained large amounts of
callose
and were infiltrated with
phenolic compounds.
Phenolic compounds, detected in transmission electron micrographs using gold-complexed laccase, accumulated in host cell walls, in intercellular spaces, and on the surface and inside of the invading pathogen’s hyphae.
2-
effect of SE34 alone or in combination with chitin on structural and cytochemical changes of tomato infected with Fusarium oxysporum f. sp. radicis-lycopersici was investigated
Treatment by strain SE34 reduced the severity of typical symptoms, including wilting of seedlings and numbers of brown lesions on lateral roots.
marked changes in the host physiology
Physiological changes elicited by strain SE34 included an
increase in host cell wall density
,
t
he accumulation of polymorphic deposits at sites of potential pathogen penetration
,
and the frequent occlusion of epidermal cells and intercellular spaces with an osmophilic, amorphous material that appeared to trap the invading fungal hyphae.
chitosan - увеличивал физиологические изменения растения-хозяина :!:
количественная оценка
using gold-complexed β-1,3-glucanase
higher amounts of
β-1,3-glucans
accumulated in roots
from plants treated with strain SE34 plus chitosan compared with that of nonbacterized, chitosan-treated plants and nontreated plants.
Interestingly, the overall chitin component of the invading pathogen was structurally preserved in roots treated with SE34 with or without chitosan at the time when hyphal degradation was apparent.
This suggests that synthesis of
chitinase
in bacterial-treated roots is not an early event in the cascade of physiological steps in signal transduction that leads to induced resistance.
B. pumilus SE34 on tomato lines
signaling pathways was tested
ISR was elicited on nahG lines,
which breakdown endogenous salicylic acid
, but not in the ethylene-insensitive NR/NR line or in the jasmonic acidinsensitive df1/df1 line
The conclusion that SE34 elicits ISR via salicylic acid-independent pathways conforms to the model with ISR elicited by Pseudomonas spp.
Different results were found with B. pumilus strain T4
transgenic line of tobacco + GUS reporter gene fused to the PR1a promoter
Elicitation of ISR by strain T4 was associated with a significant increase in GUS activity in microtiter-plate and whole-plant bioassays.
elicitation of ISR results in activation of PR1a, which is activated during
salicylic acid-dependent signaling pathway
strain T4 in Arabidopsis spp
B. pumilus T4
and
SE34
,
B. amyloliquefaciens IN937a
, and
B. subtilis GB03
were evaluated for elicitation of ISR against two different pathovars of
Pseudomonas syringae
(pvs. tomato and maculicola).
while a salicylic acid-independent pathway was dominant in the tests, a salicylic acid-dependent pathway appeared to be activated during ISR elicited by strain SE34 against one pathovar.
ISR elicited by strain SE34 was dependent on NPR1, jasmonic acid, and ethylene
ISR elicited by strain T4 was dependent on ethylene.
ISR elicited by strain T4 was independent of NPR1 and jasmonic acid.
общее
Some different pathways appear to be operable when ISR is elicited by selected strains of Bacillus spp. than when ISR is elicited by Pseudomonas spp.
The specific signal transduction pathway that is promoted during ISR by Bacillus spp. depends on the strain, the host plant, and at least in one case, on the pathogen used on a given host.
поиск бактериальных детерменант
volatile extracts - летучие экстракты Bacillus
первичные детерминанты стимуляции роста растений и вызывания ISR
Ryu et al. (25) observed significant growth promotion of Arabidopsis spp. by B. subtilis strain GB03 and B. amyloliquefaciens strain IN937a in I-plates
When either of the two bacteria were placed on one side of I-plates, Arabidopsis plants growing on the other side of the plate exhibited enhanced growth, presumably as a result of volatiles produced by the bacteria
2,3-butanediol
and
acetoin
elicited plant growth promotion
VOCs from strains GB03 and IN937a были протестированы на мутантах Arabidopsis, включая
cytokinin-, brassinosteroid-, and gibberellic acidinsensitive mutants
auxin-transport-deficient and cytokinin receptor-deficient mutants
VOCs from strain IN937a promoted growth of all mutants
VOCs from strain GB03 did not promote growth on two lines:
the cytokinin- and ethyleneinsensitive mutant (double mutation)
the cytokinin receptordeficient mutant
Hence, the cytokinin-signaling pathway appears to play a role in growth promotion with VOCs from strain GB03 but not IN937a
exposure of Arabidopsis spp. to VOCs from strains
GB03
and
IN937a
reduction in the severity of disease caused by Erwinia carotovora subsp. carotovora.
2,3-butanediol
was found to elicit ISR in a dose-dependent manner.
Various mutant lines of Arabidopsis spp. were exposed to whole VOCs (not individual fractions).
jasmonic acid-insensitive line (coi1) жасминовая кислота
ethylene-insensitive line (ein2)
salicylic acid-degrading line (NahG)
salicylic acid constitutively producing line (crp1)
line that lacks synthesis of salicylate and activation of the regulatory gene npr1
VOCs from strain IN937a elicited ISR on all of these lines
VOCs from strain GB03 elicited ISR on all lines except the ethyleneinsensitive line
The importance of the ethylene-dependent signaling pathway for elicitation of ISR by VOCs from strain GB03
was confirmed in tests with GUS fusions as reporters for activity of the following genes: PR1a for salicylic acid, PDF1.2 for jasmonic acid and ethylene, and Jin14 for jasmonic acid.
Exposure of plants to VOCs from strain GB03 increased GUS activity of PDF1.2 but not of the other genes. This finding confirms that the ethylene pathway is involved with elicitation of ISR by VOCs from strain GB03.
общее
летучие в-ва из Bacillus вызывают индуцированную системнуюустойчивость и стимулируют рост
2,3-butanediol
стумулирует рост растений и ISR
signaling pathways for both growth promotion and ISR are different between the two strains
with strain GB03, the signaling pathway for growth promotion (cytokinindependent) appears to be different from the pathway for ISR (ethylene-dependent).
Progress toward practical use in agriculture and horticulture
Bacillus PGPR seem to have an advantage over pseudomonad PGPR
Bacillus spp. elicit both plant growth promotion and ISR
препарат Yield Shield
spore preparation of the B. pumilus strain
INR7
and designated by Gustafson,
LLC as GB34
soybeans to protect against Rhizoctonia solani and Fusarium spp
strain INR7 results in significant seedling growth promotion and in ISR
decrease in incidence and severity of Rhizoctonia solani inoculated onto stems at a point where INR7 does not colonize and by a systemic increase in lignification of plant cell walls
fungicides
no direct reports on this subject using Bacillus spp
indirect support
Montana State University on ISR against Cercospora leaf spot of sugar beet
treatment with the most widely used fungicide,
triphenyltin hydroxide
, was significantly greater than the protection resulting from B. mycoides strain Bac J in four of the six field trials
Bac J + the fungicide propiconazole
disease reduction
that was statistically equivalent to that from treatment with triphenyltin hydroxide in five of the six field trials
mixing strains of biological disease control agents can increase the repeatability of efficacy
Jetiyanon and Kloepper (10)
mixture of B. amyloliquefaciens IN937a and B. subtilis IN937b significantly protected against all the tested diseases
The mixture of strains IN937a and IN937b also resulted in significant yield increases of all crops during the rainy season and generally in significant promotion of midseason plant growth
product BioYield by Gustafson (11)
two-strain mixtures of Bacillus spp. that elicit ISR together
concept was to develop a biological formulation consisting of components known to exert different mechanisms for control of diseases.
components
chitosan for nematode control
B. subtilis strain GB03 for control of soilborne pathogens via production of the antibiotic
iturin
one of several tested strains of Bacillus spp. that elicit ISR
three-component combination (chitosan plus two bacterial strains) exhibited a more consistent and greater magnitude of growth promotion and systemic protection against pathogens than did any of the individual components
Based on the results, the two-strain combination of B. amyloliquefaciens strain IN937a and B. subtilis strain GB03 was selected for product development
Signaling pathways
Бактериальные детерменанаты