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Risk assessment of climate change variables on bacterial pathogenesis of soft rot in tomato plant

KrishiKosh

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Title Risk assessment of climate change variables on bacterial pathogenesis of soft rot in tomato plant
Ph D
 
Creator NAMITA RANI DAS
 
Contributor Anita Chaudhary
 
Subject Pectobacterium, HSL, soft rot, OHHL
 
Description T-8388
In the current climate change scenario and future predictions, the plant pathogenic
interaction is expected to become more complex. Plant pathogens cross talk among
themselves by producing and secreting certain kind of signal molecules, the mechanism
called Quorum Sensing (QS). QS signals vary in side chain length from C4 to C18,
chemically very unstable, prone to degraded by the elevated temperature, alkaline pH
etc. and activate special gene (virulent gene) expression. In Pectobacterium carotovorum
pv. carotovorum, cell wall degrading enzymes (virulent factor) is produced by this kind
of mandatory cross communication procedure (QS), which causes maceration of plant
tissue. Our aim was to evaluate the impact of climate change variables on QS mediated
pathogenesis of soft rot in tomato. From this investigation, one novel and more virulent
Pectobacterium carotovorum pv. carotovorum strain (Gene Bank Accession
no.GU590785) was isolated and found to produce C6-OHHL, C6-HHL along with one
novel QS active compound namely C10-Undecanoyl Homoserine Lactone (confirmed by
LC-MS analysis). This new compound showed 0.19 Rf value in a biosensor
(Agrobacterium tumefaciens- NTL4) mediated C18-RPTLC study and a characteristic
protonated mass (MH+
) peak at 268. LC-MS-MS of another compound with
characteristic protonated mass (MH+
) peak at 214 showed daughter ion fragmentation
pattern of m/z (71, 85, 113, 102) and finally through 1H and 13C NMR structure was
confirmed as 3-oxo-hexanoyl homoserine lactone (C6-OHHL). C6-OHHL was found to
play key role for regulating pathogenesis and the novel C10-Undecanoyl HSL was found
to stimulate the function of C6-OHHL. These signal molecules production, secretion,
distribution in the natural system were observed to be critically regulated by surrounding
environmental conditions viz. temperature, pH, carbon substrate type and concentration
etc. Growth media pH >8, C6-OHHL was found to be degraded due to lactonolysis
(lactone ring opening). At higher glucose concentration (0.5%, 0.75%, 1%) C6-OHHL
was not found but detected under lower (0.1%, 0.25%) glucose concentration. Among
different incubation temperatures, C6-OHHL was not detected at 35oC and 37oC. Disease
Severity Index (DSI) was found highest (78.923 %) in 33oC under laboratory condition.
In phytotron, among six different elevated CO2 and temperature interactions, in T3C2
(600 ppm, 28oC) maximum C6-OHHL, Cellulase and disease severity (73.18%) was
noticed. At per our best knowledge we are reporting first time C10-Undecanoyl
Homoserine Lactone from Pectobacterium carotovorum pv. carotovorum. From this
study it can be concluded that, at elevated CO2 and elevated temperature (upto a certain
limit) soft rot disease severity will be more though interactions with all the
environmental parameters, plant physiology and changing climatic variables may
complicate the effects of elevated CO2 on plant pathogenesis.
 
Date 2016-11-01T09:32:37Z
2016-11-01T09:32:37Z
2011
 
Type Thesis
 
Identifier http://krishikosh.egranth.ac.in/handle/1/83063
 
Format application/pdf
 
Publisher IARI, DIVISION OF ENVIRONMENTAL SCIENCES