[compost_tea] Phytopathology88:compost water extracts+induced resistance by Zhang & Hoitink

From: Steve Diver <steved_at_ncat.org>
Date: Wed, 20 Oct 2004 17:06:13 -0000

Another relevant article from Hoitink et al:

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Compost and Compost Water Extract-Induced Systemic Acquired
Resistance
in Cucumber and Arabidopsis.

W. Zhang, D. Y. Han, W. A. Dick, K. R. Davis, and
H. A. J. Hoitink.

Phytopathology 88: 450-455.  May 1998.  Volume 88, Number 5

Abstract:

A biocontrol agent-fortified compost mix, suppressive to several
diseases caused by soilborne plant pathogens, induced systemic
acquired resistance (SAR) in cucumber against anthracnose caused
by Colletotrichum orbiculare and in Arabidopsis against bacterial
speck caused by Pseudomonas syringae pv. maculicola KD4326.
A peat mix conducive to soilborne diseases did not induce SAR.
The population size of P. syringae pv. maculicola KD4326 was
significantly lower in leaves of Arabidopsis plants grown in
the compost mix compared to those grown in the peat mix.
Autoclaving destroyed the SAR-inducing effect of the compost
mix, and inoculation of the autoclaved mix with nonautoclaved
compost mix or Pantoea agglomerans 278A restored the effect,
suggesting the SAR-inducing activity of the compost mix was
biological in nature. Topical sprays with water extract prepared
from the compost mix reduced symptoms of bacterial speck and
the population size of pathogenic KD4326 in Arabidopsis grown
in the peat mix but not in the compost mix. The peat mix water
extract applied as a spray did not control bacterial speck on
plants grown in either mix. Topical sprays with salicylic acid
(SA) reduced the severity of bacterial speck on plants in the
peat mix but did not further reduce the severity of symptoms
on plants in the compost mix. The activity of the compost
water extract was heat-stable and passed through a 0.2-µm
membrane filter. Beta-1,3-Glucanase activity was low in
cucumber plants grown in either mix, but when infected with
C. orbiculare, this activity was induced to significantly
higher levels in plants grown in the compost mix than in
plants grown in the peat mix. Similar results were obtained
for beta-D-glucuronidase (GUS) activity driven by a PR2
(beta-1,3-glucanase) gene promoter in transgenic Arabidopsis
plants grown in the compost or peat mix. GUS activity was
induced with topical sprays of the compost water extract
or SA in plants not inoculated with the pathogen, suggesting
that compost-induced disease suppression more than likely
involved the potentiation of resistance responses rather
than their activation and that compost-induced SAR differed
from SAR induced by pathogens, SA, or compost water extract.

Additional keywords: compost-amended potting mix.

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[Excerpt:]

Water extracts from the compost or peat mix were prepared
by adding tap water to the mixes (1:1, vol/vol). These
mixtures (4 liters) were stirred thoroughly and allowed to
ferment for 1 week, according to a procedure developed by
Weltzien (46), filtered through cheesecloth, and passed
through Whatman (Maidstone, England) No. 4 filter paper
(particle retention, >20 µm).

46. Weltzien, H. C. 1992. Biocontrol of foliar fungal diseases
with compost extracts. Pages 430-450 in: Microbial Ecology
of Leaves. J. H. Andrews and S. S. Hirano, eds. Springer-Verlag,
New York.

Fyi, this Phytopathology_88 article builds on Zhang and
Hoitink's earlier classic work with disease-suppressive
composts and systemic acquired resistance in cucumber:

Zhang, W., Hoitink, H. A. J., and Dick, W. A. 1996.
Compost-induced systemic acquired resistance in cucumber
to Pythium root rot and anthracnose. Phytopathology
86: 1066-1070.

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Received on Wed Oct 20 2004 - 13:47:06 EDT

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